set "wipe_tower_extra_rib_length": "8"

With the gap wall on a multi-tool printer, quantize the ram band up to its
whole reserved rows (as the BBL tower does for the old-tool purge) and start
CP TOOLCHANGE WIPE at the left-edge boundary on a fresh row below it instead
of continuing from wherever the ram serpentine ended. The entry scrub then
runs at the wall gap on ram toolchanges too, and the wipe box is whole rows,
so it is filled completely like the no-ram case. SEMM and skip-points-off
behavior is unchanged.

resources/profiles/Snapmaker/process/fdm_process_U1_common.json

@@ -70,7 +70,7 @@
 	"wipe_tower_no_sparse_layers": "0",
 	"wipe_tower_cone_angle": "30",
 	"wipe_tower_wall_type": "rib",
-	"wipe_tower_extra_rib_length": "0",
+	"wipe_tower_extra_rib_length": "8",
 	"prime_tower_width": "35",
 	"prime_volume": "30",
 	"wall_generator": "arachne",

src/libslic3r/Config.hpp

@@ -2,6 +2,7 @@
 #define slic3r_Config_hpp_
 
 #include <assert.h>
+#include <algorithm>
 #include <map>
 #include <climits>
 #include <cfloat>
@@ -780,10 +781,14 @@ public:
                 this->values[i] = rhs_vec->values[i];
                 modified        = true;
             } else {
-                if ((i < default_index.size()) && (default_index[i] < default_value.size()))
+                // Orca: a negative slot (failed variant lookup) must not silently collapse the
+                // whole array to the first slot's value — the int-vs-size_t comparison used to
+                // promote -1 past the bounds check. Keep the slot's own value (get_at-style
+                // clamp) when no valid index is available.
+                if ((i < default_index.size()) && (default_index[i] >= 0) && (size_t(default_index[i]) < default_value.size()))
                     this->values[i] = default_value[default_index[i]];
                 else
-                    this->values[i] = default_value[0];
+                    this->values[i] = default_value[std::min(i, default_value.size() - 1)];
             }
         }
         return modified;
@@ -2106,6 +2111,11 @@ public:
             throw ConfigurationError("ConfigOptionEnumGeneric: Assigning an incompatible type");
         // rhs could be of the following type: ConfigOptionEnumGeneric or ConfigOptionEnum<T>
         this->value = rhs->getInt();
+        // Orca: options embedded in a StaticPrintConfig are constructed without a keys_map;
+        // adopt the source's so a later serialize() can emit names.
+        if (this->keys_map == nullptr)
+            if (auto rhs_generic = dynamic_cast<const ConfigOptionEnumGeneric *>(rhs))
+                this->keys_map = rhs_generic->keys_map;
     }
 
     std::string serialize() const override
@@ -2162,7 +2172,12 @@ public:
         if (rhs->type() != this->type())
             throw ConfigurationError("ConfigOptionEnumGeneric: Assigning an incompatible type");
         // rhs could be of the following type: ConfigOptionEnumsGeneric
-        this->values = dynamic_cast<const ConfigOptionEnumsGenericTempl *>(rhs)->values;
+        auto rhs_enums = dynamic_cast<const ConfigOptionEnumsGenericTempl *>(rhs);
+        this->values = rhs_enums->values;
+        // Orca: options embedded in a StaticPrintConfig are constructed without a keys_map;
+        // adopt the source's so a later serialize() emits names instead of empty tokens.
+        if (this->keys_map == nullptr)
+            this->keys_map = rhs_enums->keys_map;
     }
 
     std::string serialize() const override

src/libslic3r/GCode.cpp

@@ -13,6 +13,7 @@
 #include "GCode/PrintExtents.hpp"
 #include "GCode/Thumbnails.hpp"
 #include "GCode/WipeTower.hpp"
+#include "GCode/WipeTower2.hpp"
 #include "ShortestPath.hpp"
 #include "Print.hpp"
 #include "Utils.hpp"
@@ -888,6 +889,65 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
         return res;
     }
 
+    // Type2 tower-local point -> bed frame. The rib-wall offset is tower-local, so it
+    // rotates with the tower (unlike the BBL tower in append_tcr, which never rotates).
+    Vec2f WipeTowerIntegration::transform_wt2_pt(const Vec2f &pt) const
+    {
+        const float alpha = m_wipe_tower_rotation / 180.f * float(M_PI);
+        return Eigen::Rotation2Df(alpha) * (pt + m_rib_offset) + m_wipe_tower_pos;
+    }
+
+    // Printable-area bounds for tower-approach routing, in object coordinates (shared by
+    // the BBL avoid-perimeter path in append_tcr and the Type2 skip-points router).
+    // Multi-nozzle: clamp the travel bounds to the region every extruder can reach
+    // (get_extruder_shared_printable_polygon) instead of the full bed. Gated on the
+    // multi-nozzle predicate so every existing single/dual printer keeps the historic
+    // full-printable_area routing byte-identical.
+    BoundingBox WipeTowerIntegration::printer_travel_bounds(GCode &gcodegen) const
+    {
+        const Vec2f plate_origin_2d(m_plate_origin(0), m_plate_origin(1));
+        BoundingBox printer_bbx;
+        if (is_multi_nozzle_printer(gcodegen.m_config)) {
+            printer_bbx     = get_extents(gcodegen.m_print->get_extruder_shared_printable_polygon());
+            printer_bbx.min = wipe_tower_point_to_object_point(gcodegen, unscaled<float>(printer_bbx.min) + plate_origin_2d);
+            printer_bbx.max = wipe_tower_point_to_object_point(gcodegen, unscaled<float>(printer_bbx.max) + plate_origin_2d);
+        } else {
+            Points bed_points;
+            for (const auto& p : gcodegen.m_config.printable_area.values)
+                bed_points.push_back(wipe_tower_point_to_object_point(gcodegen, p.cast<float>() + plate_origin_2d));
+            printer_bbx = BoundingBox(bed_points);
+        }
+        return printer_bbx;
+    }
+
+    // With skip points enabled the Type2 tower wall has an opening at each toolchange's
+    // entry (tcr.start_pos): route the approach around the tower's bounding box so the
+    // nozzle enters through that opening instead of dragging across the printed wall
+    // (append_tcr parity). Emits only the waypoints leading up to the opening — the
+    // caller still travels to start_wipe_pos itself. Returns an empty string when the
+    // gap wall is off (option off or cone wall) or the approach already starts inside
+    // the tower: such hops never cross the wall and must stay direct.
+    std::string WipeTowerIntegration::travel_to_tower_gap(GCode &gcodegen, const Point &route_start, const Point &start_wipe_pos) const
+    {
+        if (!WipeTower2::use_gap_wall(gcodegen.m_config))
+            return {};
+        const Vec2f plate_origin_2d(m_plate_origin(0), m_plate_origin(1));
+        // Transform the tower-local bbx corners exactly like the tcr points; a rotated
+        // tower gets a conservative axis-aligned envelope.
+        Polygon avoid_points = scaled(m_wipe_tower_bbx).polygon();
+        for (auto& p : avoid_points.points)
+            p = wipe_tower_point_to_object_point(gcodegen, transform_wt2_pt(unscale(p).cast<float>()) + plate_origin_2d);
+        BoundingBox avoid_bbx(avoid_points.points);
+        if (avoid_bbx.contains(route_start))
+            return {};
+        Polyline    travel_polyline = generate_path_to_wipe_tower(route_start, start_wipe_pos, avoid_bbx, printer_travel_bounds(gcodegen));
+        std::string gcode;
+        // The polyline's last point is start_wipe_pos itself — emitted by the caller.
+        for (size_t i = 0; i + 1 < travel_polyline.points.size(); ++i)
+            gcode += gcodegen.travel_to(travel_polyline.points[i], erMixed, "Travel to a Wipe Tower");
+        return gcode;
+    }
+
     std::string WipeTowerIntegration::append_tcr(GCode& gcodegen, const WipeTower::ToolChangeResult& tcr, int new_filament_id, double z) const
     {
         if (new_filament_id != -1 && new_filament_id != tcr.new_tool)
@@ -998,6 +1058,7 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
         std::string change_filament_gcode = gcodegen.config().change_filament_gcode.value;
 
         bool is_used_travel_avoid_perimeter = gcodegen.m_config.prime_tower_skip_points.value;
+        if (is_nozzle_change && !tcr.nozzle_change_result.is_extruder_change) is_used_travel_avoid_perimeter = false;
 
         // add nozzle change gcode into change filament gcode
         std::string nozzle_change_gcode_trans;
@@ -1260,24 +1321,7 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
                 Vec2f       gcode_last_pos2d{gcode_last_pos[0], gcode_last_pos[1]};
                 Point       gcode_last_pos2d_object = gcodegen.gcode_to_point(gcode_last_pos2d.cast<double>() + plate_origin_2d.cast<double>());
                 Point       start_wipe_pos          = wipe_tower_point_to_object_point(gcodegen, tool_change_start_pos + plate_origin_2d);
-                BoundingBox avoid_bbx, printer_bbx;
-                {
-                    // set printer_bbx
-                    // Multi-nozzle: clamp the avoid-perimeter travel bounds to the region every
-                    // extruder can reach (get_extruder_shared_printable_polygon) instead of the full
-                    // bed. Gated on the multi-nozzle predicate so H2D and every existing single/dual
-                    // printer keep the historic full-printable_area routing byte-identical.
-                    if (is_multi_nozzle_printer(gcodegen.m_config)) {
-                        printer_bbx     = get_extents(gcodegen.m_print->get_extruder_shared_printable_polygon());
-                        printer_bbx.min = wipe_tower_point_to_object_point(gcodegen, unscaled<float>(printer_bbx.min) + plate_origin_2d);
-                        printer_bbx.max = wipe_tower_point_to_object_point(gcodegen, unscaled<float>(printer_bbx.max) + plate_origin_2d);
-                    } else {
-                        Pointfs bed_pointsf = gcodegen.m_config.printable_area.values;
-                        Points  bed_points;
-                        for (auto p : bed_pointsf) { bed_points.push_back(wipe_tower_point_to_object_point(gcodegen, p.cast<float>() + plate_origin_2d)); }
-                        printer_bbx = BoundingBox(bed_points);
-                    }
-                }
+                BoundingBox avoid_bbx, printer_bbx = printer_travel_bounds(gcodegen);
                 {
                     // set avoid_bbx
                     avoid_bbx            = scaled(m_wipe_tower_bbx);
@@ -1307,20 +1351,23 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
         }
 
         // do unretract after setting current extruder_id
-        // PETG filaments on a device with a filament switcher get a small (2 mm) pre-extrusion
-        // before the tool change. has_filament_switcher is a develop-only key read defensively from the
-        // full config (Orca does not carry it as a static PrintConfig member — same convention as
-        // enable_filament_dynamic_map); no shipping profile sets it (grep resources/profiles = 0), so
-        // is_petg_pre_extrusion is always false -> extra_unretract stays 0 -> byte-identical to the plain
-        // unretract() fleet-wide. The tower-interface contact pre-extrusion length (the
-        // is_contact_pre_extrusion branch) is NOT applied here; it is only computed as the guard used to
-        // give the contact path priority over PETG.
+        // BBS pattern: the wipe tower shifts the toolchange start position outward for the
+        // tower-interface (contact) pre-extrusion and for the PETG-with-filament-switcher case;
+        // the pre-extrusion material itself is laid down here as extra unretract on the approach.
+        // has_filament_switcher is a develop-only key read defensively from the full config (Orca
+        // does not carry it as a static PrintConfig member — same convention as
+        // enable_filament_dynamic_map); no shipping profile sets it, so is_petg_pre_extrusion is
+        // always false fleet-wide.
         const ConfigOptionBool* has_filament_switcher_opt = gcodegen.m_print->full_print_config().option<ConfigOptionBool>("has_filament_switcher");
         bool is_contact_pre_extrusion = tcr.is_contact && gcodegen.m_config.enable_tower_interface_features;
         bool is_petg_pre_extrusion    = !is_contact_pre_extrusion
                                         && gcodegen.config().filament_type.get_at(tcr.new_tool) == "PETG"
                                         && has_filament_switcher_opt && has_filament_switcher_opt->value;
-        float extra_unretract = is_petg_pre_extrusion ? 2.f : 0.f;
+        float extra_unretract = 0.f;
+        if (is_contact_pre_extrusion)
+            extra_unretract = gcodegen.m_config.filament_tower_interface_pre_extrusion_length.get_at(tcr.new_tool);
+        else if (is_petg_pre_extrusion)
+            extra_unretract = 2.f;
         std::string toolchange_unretract_str = (extra_unretract > 0.f) ? gcodegen.unretract(extra_unretract) : gcodegen.unretract();
         check_add_eol(toolchange_unretract_str);
 
@@ -1418,20 +1465,16 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
         // We want to rotate and shift all extrusions (gcode postprocessing) and starting and ending position
         float alpha = m_wipe_tower_rotation / 180.f * float(M_PI);
 
-        auto transform_wt_pt = [&alpha, this](const Vec2f &pt) -> Vec2f {
-            Vec2f out = Eigen::Rotation2Df(alpha) * pt;
-            out += m_wipe_tower_pos;
-            return out;
-        };
-
+        // Priming lines are absolute bed moves; everything else is tower-local
+        // (transform_wt2_pt).
         Vec2f start_pos = tcr.start_pos;
         Vec2f end_pos   = tcr.end_pos;
         if (!tcr.priming) {
-            start_pos = transform_wt_pt(start_pos);
-            end_pos   = transform_wt_pt(end_pos);
+            start_pos = transform_wt2_pt(start_pos);
+            end_pos   = transform_wt2_pt(end_pos);
         }
 
-        Vec2f wipe_tower_offset   = tcr.priming ? Vec2f::Zero() : m_wipe_tower_pos;
+        Vec2f wipe_tower_offset   = tcr.priming ? Vec2f::Zero() : Vec2f(m_wipe_tower_pos + Eigen::Rotation2Df(alpha) * m_rib_offset);
         float wipe_tower_rotation = tcr.priming ? 0.f : alpha;
         Vec2f plate_origin_2d(m_plate_origin(0), m_plate_origin(1));
 
@@ -1461,16 +1504,22 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
                                                              || is_ramming
                                                              || tool_change_on_wipe_tower);
 
-        if (should_travel_to_tower || gcodegen.m_need_change_layer_lift_z) {
+        const Point start_wipe_pos     = wipe_tower_point_to_object_point(gcodegen, start_pos + plate_origin_2d);
+        const bool travel_to_tower_now = should_travel_to_tower || gcodegen.m_need_change_layer_lift_z;
+        if (travel_to_tower_now) {
             // FIXME: It would be better if the wipe tower set the force_travel flag for all toolchanges,
             // then we could simplify the condition and make it more readable.
             gcode += gcodegen.retract();
             gcodegen.m_avoid_crossing_perimeters.use_external_mp_once();
-            gcode += gcodegen.travel_to(wipe_tower_point_to_object_point(gcodegen, start_pos + plate_origin_2d), erMixed, "Travel to a Wipe Tower");
+            if (!tcr.priming && gcodegen.last_pos_defined())
+                gcode += travel_to_tower_gap(gcodegen, gcodegen.last_pos(), start_wipe_pos);
+            gcode += gcodegen.travel_to(start_wipe_pos, erMixed, "Travel to a Wipe Tower");
             gcode += gcodegen.unretract();
         } else {
             // When this is multiextruder printer without any ramming, we can just change
-            // the tool without travelling to the tower.
+            // the tool without travelling to the tower. The tower entry travel then lives
+            // inside the tcr gcode; with skip points on it is rerouted below, once the
+            // toolchange gcode (and the head position it ends at) is known.
         }
 
         if (will_go_down) {
@@ -1493,6 +1542,36 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
                 toolchange_temp_override = interface_temp;
             }
             toolchange_gcode_str = gcodegen.set_extruder(new_extruder_id, tcr.print_z, false, toolchange_temp_override); // TODO: toolchange_z vs print_z
+            if (!travel_to_tower_now && !tcr.priming && WipeTower2::use_gap_wall(gcodegen.m_config)) {
+                // The tool changed in place (multi-tool printer without ramming), so the
+                // tower entry is the tcr's own positioning move — a straight line across
+                // the printed wall. Route it around the tower and in through the wall
+                // opening instead, riding at the end of the change_filament_gcode
+                // substitution so the generator's positioning move degrades to a
+                // zero-length one (append_tcr parity: travel after the filament change,
+                // retracted, with the new filament).
+                Vec3f last_gcode_pos = gcodegen.writer().get_position().cast<float>();
+                Point route_start;
+                bool  have_start = false;
+                if (GCodeProcessor::get_last_position_from_gcode(toolchange_gcode_str, last_gcode_pos)) {
+                    // A custom change_filament_gcode may have moved the head (tool docks
+                    // etc.); recover the real position from the emitted gcode.
+                    route_start = gcodegen.gcode_to_point(Vec2d(last_gcode_pos.x(), last_gcode_pos.y()) + plate_origin_2d.cast<double>());
+                    have_start  = true;
+                } else if (gcodegen.last_pos_defined()) {
+                    route_start = gcodegen.last_pos();
+                    have_start  = true;
+                }
+                if (have_start) {
+                    gcodegen.set_last_pos(route_start);
+                    gcodegen.m_avoid_crossing_perimeters.use_external_mp_once();
+                    std::string travel = travel_to_tower_gap(gcodegen, route_start, start_wipe_pos);
+                    travel += gcodegen.travel_to(start_wipe_pos, erMixed, "Travel to a Wipe Tower");
+                    check_add_eol(travel);
+                    toolchange_gcode_str += travel;
+                    gcodegen.set_last_pos(start_wipe_pos);
+                }
+            }
             if (gcodegen.config().enable_prime_tower) {
                 deretraction_str += gcodegen.writer().travel_to_z(z, "Force restore layer Z", true);
                 Vec3d position{gcodegen.writer().get_position()};
@@ -1678,7 +1757,7 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
             // Prepare a future wipe.
             gcodegen.m_wipe.reset_path();
             for (const Vec2f& wipe_pt : tcr.wipe_path)
-                gcodegen.m_wipe.path.points.emplace_back(wipe_tower_point_to_object_point(gcodegen, transform_wt_pt(wipe_pt) + plate_origin_2d));
+                gcodegen.m_wipe.path.points.emplace_back(wipe_tower_point_to_object_point(gcodegen, transform_wt2_pt(wipe_pt) + plate_origin_2d));
         }
 
         // Let the planner know we are traveling between objects.

src/libslic3r/GCode.hpp

@@ -132,6 +132,9 @@ private:
     std::string append_tcr(GCode &gcodegen, const WipeTower::ToolChangeResult &tcr, int new_extruder_id, double z = -1.) const;
     Polyline generate_path_to_wipe_tower(const Point &start_pos, const Point &end_pos, const BoundingBox &avoid_polygon, const BoundingBox &printer_bbx) const;
     std::string append_tcr2(GCode &gcodegen, const WipeTower::ToolChangeResult &tcr, int new_extruder_id, double z = -1.) const;
+    std::string travel_to_tower_gap(GCode &gcodegen, const Point &route_start, const Point &start_wipe_pos) const;
+    Vec2f transform_wt2_pt(const Vec2f &pt) const;
+    BoundingBox printer_travel_bounds(GCode &gcodegen) const;
 
     // Postprocesses gcode: rotates and moves G1 extrusions and returns result
     std::string post_process_wipe_tower_moves(const WipeTower::ToolChangeResult& tcr, const Vec2f& translation, float angle) const;

src/libslic3r/GCode/GCodeProcessor.cpp

@@ -1450,8 +1450,8 @@ void GCodeProcessor::run_post_process()
     // flag) runs none of this. It is pure data construction — it only fills m_filament_blocks /
     // m_extruder_blocks / m_machine_*_gcode_*_line_id and never touches the exported g-code, so even
     // the enable_pre_heating fleet stays byte-identical (nothing reads the blocks until the injection
-    // pass). In practice it also stays empty/degenerate today because no template/code yet emits the
-    // MACHINE_*_GCODE_* / NOZZLE_CHANGE_* / CP_TOOLCHANGE_WIPE markers it keys off.
+    // pass). The wipe tower emits the NOZZLE_CHANGE_* (ramming) and CP_TOOLCHANGE_WIPE markers this
+    // builder keys off; the MACHINE_*_GCODE_* markers come from the machine g-code templates.
     m_filament_blocks.clear();
     m_extruder_blocks.clear();
     m_machine_start_gcode_end_line_id = (unsigned int) (-1);

src/libslic3r/GCode/PrintExtents.cpp

@@ -143,7 +143,8 @@ BoundingBoxf get_wipe_tower_extrusions_extents(const Print &print, const coordf_
     double wipe_tower_y = print.config().wipe_tower_y.get_at(plate_idx) + plate_origin(1);
     Transform2d trafo =
         Eigen::Translation2d(wipe_tower_x, wipe_tower_y) *
-        Eigen::Rotation2Dd(Geometry::deg2rad(print.config().wipe_tower_rotation_angle.value));
+        Eigen::Rotation2Dd(Geometry::deg2rad(print.config().wipe_tower_rotation_angle.value)) *
+        Eigen::Translation2d(print.wipe_tower_data().rib_offset.cast<double>()); // tower-local rib-wall shift, zero unless rib
 
     BoundingBoxf bbox;
     for (const std::vector<WipeTower::ToolChangeResult> &tool_changes : print.wipe_tower_data().tool_changes) {

src/libslic3r/GCode/WipeTower.hpp

@@ -12,7 +12,7 @@
 #include "libslic3r/Polyline.hpp"
 #include "libslic3r/TriangleMesh.hpp"
 #include <unordered_set>
-
+#include "libslic3r/MultiNozzleUtils.hpp"
 namespace Slic3r
 {
 
@@ -20,6 +20,11 @@ class WipeTowerWriter;
 class PrintConfig;
 enum GCodeFlavor : unsigned char;
 
+// Cuts the tower wall polygon open at each skip point (a toolchange's entry position)
+// so the entry travel can pass through instead of crossing the printed wall. Defined in
+// WipeTower.cpp, shared by WipeTower and WipeTower2.
+Polylines contrust_gap_for_skip_points(
+    const Polygon& polygon, const std::vector<Vec2f>& skip_points, float wt_width, float gap_length, Polygon& insert_skip_polygon);
 
 class WipeTower
 {
@@ -84,7 +89,6 @@ public:
         bool                    priming;
 
 		bool                    is_tool_change{false};
-        bool                    is_contact{false};
 		Vec2f                   tool_change_start_pos;
 
         // Pass a polyline so that normal G-code generator can do a wipe for us.
@@ -108,6 +112,7 @@ public:
         // executing the gcode finish_layer_tcr.
         bool is_finish_first = false;
 
+        bool               is_contact = false;
         NozzleChangeResult nozzle_change_result;
 
 		// Sum the total length of the extrusion.
@@ -122,6 +127,8 @@ public:
 			}
 			return e_length;
 		}
+		// Orca: set by WipeTower2 (non-BBL tower) to force a travel to the tower even when the
+		// previous position is unknown; read by WipeTowerIntegration::append_tcr2 (GCode.cpp).
 		bool force_travel = false;
 	};
 
@@ -162,15 +169,12 @@ public:
                                    bool priming,
                                    size_t old_tool,
                                    bool is_finish,
-                                   bool is_tool_change,
-                                   float purge_volume,
-                                   bool is_contact = false) const;
+		                           bool is_tool_change, float purge_volume, bool is_contact) const;
 
     ToolChangeResult construct_block_tcr(WipeTowerWriter& writer,
                                    bool priming,
                                    size_t filament_id,
-                                   bool is_finish,
-                                   float purge_volume) const;
+                                   bool is_finish, float purge_volume) const;
 
 
 	// x			-- x coordinates of wipe tower in mm ( left bottom corner )
@@ -184,9 +188,14 @@ public:
 	// Set the extruder properties.
     void set_extruder(size_t idx, const PrintConfig& config);
 
+    void set_shared_print_bed(const Polygons &bed) { m_shared_print_bed = bed; }
+    // Orca: has_filament_switcher is not a static PrintConfig member here, so it is pushed in from
+    // Print via a setter rather than read in the ctor. Device-set only.
+    void set_has_filament_switcher(bool v) { m_has_filament_switcher = v; }
 	// Appends into internal structure m_plan containing info about the future wipe tower
 	// to be used before building begins. The entries must be added ordered in z.
-	void plan_toolchange(float z_par, float layer_height_par, unsigned int old_tool, unsigned int new_tool, float wipe_volume = 0.f, float prime_volume = 0.f);
+    void plan_toolchange(float z_par, float layer_height_par, unsigned int old_tool, unsigned int new_tool, float wipe_volume_ec = 0.f, float wipe_volume_nc = 0.f, float prime_volume = 0.f);
+
 
 	// Iterates through prepared m_plan, generates ToolChangeResults and appends them to "result"
 	void generate(std::vector<std::vector<ToolChangeResult>> &result);
@@ -219,9 +228,6 @@ public:
 		}
 	}
 
-	void set_wipe_volume(std::vector<std::vector<float>>& wiping_matrix) {
-		wipe_volumes = wiping_matrix;
-	}
 
 	// Switch to a next layer.
 	void set_layer(
@@ -250,7 +256,6 @@ public:
 
 		// Calculate extrusion flow from desired line width, nozzle diameter, filament diameter and layer_height:
 		m_extrusion_flow = extrusion_flow(layer_height);
-
         // Advance m_layer_info iterator, making sure we got it right
 		while (!m_plan.empty() && m_layer_info->z < print_z - WT_EPSILON && m_layer_info+1 != m_plan.end())
 			++m_layer_info;
@@ -309,20 +314,9 @@ public:
     std::vector<float> get_used_filament() const { return m_used_filament_length; }
     int get_number_of_toolchanges() const { return m_num_tool_changes; }
 
-	void set_filament_map(const std::vector<int> &filament_map) { m_filament_map = filament_map; }
-	// Vortek H2C: filament_id → physical nozzle_id for carousel rotation detection
-	void set_filament_nozzle_map(const std::vector<int> &nozzle_map) { m_filament_nozzle_map = nozzle_map; }
-
 	void set_has_tpu_filament(bool has_tpu) { m_has_tpu_filament = has_tpu; }
+
     bool has_tpu_filament() const { return m_has_tpu_filament; }
-
-    // Orca: has_filament_switcher is not a static PrintConfig member, so it is pushed in from Print
-    // via a setter rather than read in the ctor. Device-set only.
-    void set_has_filament_switcher(bool v) { m_has_filament_switcher = v; }
-    // The region every extruder can reach, used to clamp the PETG pre-extrusion offset to the
-    // printable bed.
-    void set_shared_print_bed(const Polygons &bed) { m_shared_print_bed = bed; }
-
     struct FilamentParameters {
         std::string 	    material = "PLA";
         int                 category;
@@ -331,15 +325,15 @@ public:
         bool                is_support = false;
         int  			    nozzle_temperature = 0;
         int  			    nozzle_temperature_initial_layer = 0;
-        int                 interface_print_temperature = 0;
-        float               loading_speed = 0.f;
-        float               loading_speed_start = 0.f;
-        float               unloading_speed = 0.f;
-        float               unloading_speed_start = 0.f;
-        float               delay = 0.f ;
-        int                 cooling_moves = 0;
-        float               cooling_initial_speed = 0.f;
-        float               cooling_final_speed = 0.f;
+        // BBS: remove useless config
+        //float               loading_speed = 0.f;
+        //float               loading_speed_start = 0.f;
+        //float               unloading_speed = 0.f;
+        //float               unloading_speed_start = 0.f;
+        //float               delay = 0.f ;
+        //int                 cooling_moves = 0;
+        //float               cooling_initial_speed = 0.f;
+        //float               cooling_final_speed = 0.f;
         float               ramming_line_width_multiplicator = 1.f;
         float               ramming_step_multiplicator = 1.f;
         float               max_e_speed = std::numeric_limits<float>::max();
@@ -349,41 +343,41 @@ public:
         float               retract_length;
         float               retract_speed;
         float               wipe_dist;
-        float               tower_interface_pre_extrusion_dist = 0.f;
-        float               tower_interface_pre_extrusion_length = 0.f;
-        // Outward shift of the wipe start for a PETG pre-extrusion on filament-switcher devices;
-        // set from filament_tower_interface_pre_extrusion_dist.
-        float               petg_pre_extrusion_offset_dist = 0.f;
-        float               tower_ironing_area = 4.f;
-        float               tower_interface_purge_length = 0.f;
-        // Distance (in mm of filament) that a hotend is allowed to pre-cool before the
-        // tower is reached; drives the prime-tower heating-during-wipe model (multi-nozzle only).
-        float               filament_cooling_before_tower = 0.f;
-        // .first = extruder change, .second = nozzle change (carousel)
-        std::pair<float,float>  max_e_ramming_speed{0.f, 0.f};
-        std::pair<float,float>  ramming_travel_time{0.f, 0.f};
-        std::pair<int,int>      precool_target_temp{0, 0};
-        std::pair<std::vector<float>,std::vector<float>> precool_t;
-        std::pair<std::vector<float>,std::vector<float>> precool_t_first_layer;
+        std::pair<float,float>  max_e_ramming_speed;//[0]extruder change [1]nozzle change
+        std::pair<float, float> ramming_travel_time; // Travel time after ramming
+        std::pair<std::vector<float>,std::vector<float>>  precool_t;//Pre-cooling time, set to 0 to ensure the ramming speed is controlled solely by ramming volumetric speed.
+        std::pair<std::vector<float>, std::vector<float>> precool_t_first_layer;
+        std::pair<int,int>    precool_target_temp;
+        float filament_cooling_before_tower = 0.f;
+        float flat_iron_area;
+        float filament_tower_interface_print_temp;
+        float filament_tower_interface_pre_extrusion_dist = 0;
+        float filament_tower_interface_pre_extrusion_length = 0;
+        float filament_petg_pre_extrusion_offset_dist = 0;
     };
 
 
-	void set_used_filament_ids(const std::vector<int> &used_filament_ids) { m_used_filament_ids = used_filament_ids; };
+    void set_used_filament_ids(const std::vector<int> &used_filament_ids) { m_used_filament_ids = used_filament_ids; };
     void set_filament_categories(const std::vector<int> & filament_categories) { m_filament_categories = filament_categories;};
-	std::vector<int> m_used_filament_ids;
+    void set_nozzle_group_result(const MultiNozzleUtils::LayeredNozzleGroupResult &multi_nozzle_group_result) { m_multi_nozzle_group_result = &multi_nozzle_group_result; };
+    std::vector<int> m_used_filament_ids;
     std::vector<int> m_filament_categories;
+    const MultiNozzleUtils::LayeredNozzleGroupResult *m_multi_nozzle_group_result{nullptr};
+
+    enum class WipeTowerLayerType : unsigned char { Normal, Contact, Solid, Contact_UP};// Contact layer should be solid and reduce feed
 
 	struct WipeTowerBlock
     {
         int              block_id{0};
         int              filament_adhesiveness_category{0};
         std::vector<float>      layer_depths;
-		std::vector<bool>       solid_infill;
+        //std::vector<bool>       solid_infill;
         std::vector<float>      finish_depth{0}; // the start pos of finish frame for every layer
+        std::vector<WipeTowerLayerType> layers_type;     // type of the layer, normal, Contact or Solid
         float            depth{0};
         float            start_depth{0};
         float            cur_depth{0};
-		int              last_filament_change_id{-1};
+        int              last_filament_change_id{-1};
         int              last_nozzle_change_id{-1};
 	};
 
@@ -403,25 +397,33 @@ public:
     WipeTowerBlock* get_block_by_category(int filament_adhesiveness_category, bool create);
     void add_depth_to_block(int filament_id, int filament_adhesiveness_category, float depth, bool is_nozzle_change = false);
 	int get_filament_category(int filament_id);
-	bool is_in_same_extruder(int filament_id_1, int filament_id_2);
-	// Vortek H2C: format BBS-compatible NOZZLE_CHANGE_START/END tag with OF/NF/ON/NN payload
-	std::string format_nozzle_change_tag(bool start, int old_filament_id, int new_filament_id) const;
 	void reset_block_status();
     int get_wall_filament_for_all_layer();
 	// for generate new wipe tower
     void generate_new(std::vector<std::vector<WipeTower::ToolChangeResult>> &result);
 
 	void plan_tower_new();
-	void generate_wipe_tower_blocks();
+	void generate_wipe_tower_blocks(bool add_solid_flag);
     void update_all_layer_depth(float wipe_tower_depth);
-
+    void set_nozzle_last_layer_id();
+    void set_first_layer_flow_ratio(const float flow_ratio);
+    // Orca: default/initial-layer/travel acceleration are object-scope options here (PrintConfig
+    // members in BBS), so Print pushes the resolved per-variant columns in via this setter.
+    void set_accelerations(const std::vector<double> &normal, const std::vector<double> &first_layer_normal,
+                           const std::vector<double> &travel, const std::vector<double> &first_layer_travel);
+    void calc_block_infill_gap();
     ToolChangeResult   tool_change_new(size_t new_tool, bool solid_change = false, bool solid_nozzlechange=false);
-    NozzleChangeResult nozzle_change_new(int old_filament_id, int new_filament_id, bool solid_change = false);
+    NozzleChangeResult ramming(int old_filament_id, int new_filament_id, bool solid_change = false, bool extruder_change = true); // extruder_chang means nozzle_change
     ToolChangeResult   finish_layer_new(bool extrude_perimeter = true, bool extrude_fill = true, bool extrude_fill_wall = true);
     ToolChangeResult   finish_block(const WipeTowerBlock &block, int filament_id, bool extrude_fill = true);
-    ToolChangeResult   finish_block_solid(const WipeTowerBlock &block, int filament_id, bool extrude_fill = true ,bool interface_solid =false);
+    ToolChangeResult   finish_block_solid(const WipeTowerBlock &block, int filament_id, bool extrude_fill = true, WipeTowerLayerType layer_type = WipeTowerLayerType::Normal);
     void toolchange_wipe_new(WipeTowerWriter &writer, const box_coordinates &cleaning_box, float wipe_length,bool solid_toolchange=false);
     Vec2f              get_rib_offset() const { return m_rib_offset; }
+    bool               is_need_ramming(int filament_id_1, int filament_id_2, int layer_id) const;
+    bool               is_same_extruder(int filament_id_1, int filament_id_2, int layer_id) const;
+    bool               is_same_nozzle(int filament_id_1, int filament_id_2, int layer_id) const;
+    int                get_nozzle_id(int filament_id, int layer_id) const;
+    int                get_extruder_id(int filament_id, int layer_id) const;
 
 private:
 	enum wipe_shape // A fill-in direction
@@ -441,7 +443,6 @@ private:
     bool   m_enable_wrapping_detection = false;
 	bool   m_enable_timelapse_print = false;
 	bool   m_semm               = true; // Are we using a single extruder multimaterial printer?
-	bool   m_purge_in_prime_tower = false; // Do we purge in the prime tower?
     Vec2f  m_wipe_tower_pos; 			// Left front corner of the wipe tower in mm.
 	float  m_wipe_tower_width; 			// Width of the wipe tower.
 	float  m_wipe_tower_depth 	= 0.f; 	// Depth of the wipe tower
@@ -459,12 +460,11 @@ private:
     float  m_travel_speed       = 0.f;
     float  m_first_layer_speed  = 0.f;
     size_t m_first_layer_idx    = size_t(-1);
-
-    std::vector<double> m_filaments_change_length;
+    Vec2f            m_origin;
+    std::vector<int>    m_last_layer_id;
+    std::pair<std::vector<double>,std::vector<double>> m_filaments_change_length;//[0]extruder change [1]nozzle change
     size_t       m_cur_layer_id;
     NozzleChangeResult m_nozzle_change_result;
-    std::vector<int>   m_filament_map;
-    std::vector<int>   m_filament_nozzle_map;  // Vortek H2C: filament_id → physical nozzle_id
     bool               m_has_tpu_filament{false};
     bool               m_is_multi_extruder{false};
     bool               m_use_gap_wall{false};
@@ -475,33 +475,32 @@ private:
     bool               m_used_fillet{false};
     Vec2f              m_rib_offset{Vec2f(0.f, 0.f)};
     bool               m_tower_framework{false};
-
+    bool               m_need_reverse_travel{false};
+    bool               m_enable_tower_interface_features{false};
 	// G-code generator parameters.
-    float           m_cooling_tube_retraction   = 0.f;
-    float           m_cooling_tube_length       = 0.f;
-    float           m_parking_pos_retraction    = 0.f;
-    float           m_extra_loading_move        = 0.f;
+    // BBS: remove useless config
+    //float           m_cooling_tube_retraction   = 0.f;
+    //float           m_cooling_tube_length       = 0.f;
+    //float           m_parking_pos_retraction    = 0.f;
+    //float           m_extra_loading_move        = 0.f;
     float           m_bridging                  = 0.f;
     bool            m_no_sparse_layers          = false;
-    bool            m_set_extruder_trimpot      = false;
+    // BBS: remove useless config
+    //bool            m_set_extruder_trimpot      = false;
     bool            m_adhesion                  = true;
     GCodeFlavor     m_gcode_flavor;
-
-    // Multi-nozzle prime-tower heating during wipe. m_is_multiple_nozzle gates the whole
-    // feature; it is false for every current (single-nozzle) printer (extruder_max_nozzle_count
-    // defaults to 1), so the pre-heat/pre-cool path is inert and wipe-tower g-code is unchanged.
-    bool                m_is_multiple_nozzle = false;
-    std::vector<double> m_hotend_heating_rate;     // config.hotend_heating_rate (deg/s per extruder)
-    std::vector<int>    m_physical_extruder_map;   // logical extruder -> physical tool number (M104 T param)
-
-    // Per-extruder printable-height clamp. m_printable_height = config.extruder_printable_height
-    // (per-extruder Z limit; empty for single-extruder printers, [320,325] for H2D). m_last_layer_id
-    // records, per extruder, the last wipe-tower layer that uses it. is_valid_last_layer() is gated on
-    // m_is_multi_extruder so single-extruder wipe-tower g-code is unchanged; the clamp only bites a
-    // multi-extruder wipe tower whose final per-extruder layer exceeds that extruder's printable
-    // height (near the Z limit).
-    std::vector<double> m_printable_height;
-    std::vector<int>    m_last_layer_id;
+    bool                      m_is_multiple_nozzle = false;
+    std::vector<unsigned int> m_normal_accels;
+    std::vector<unsigned int> m_first_layer_normal_accels;
+    std::vector<unsigned int> m_travel_accels;
+    std::vector<unsigned int> m_first_layer_travel_accels;
+    unsigned int              m_max_accels;
+    bool                      m_accel_to_decel_enable;
+    float                     m_accel_to_decel_factor;
+    bool                      m_enable_arc_fitting = true;
+    std::vector<double>       m_hotend_heating_rate;
+    std::vector<double>       m_hotend_cooling_rate;
+    Polygons                  m_shared_print_bed;
 
     // Bed properties
     enum {
@@ -512,10 +511,11 @@ private:
     float m_bed_width; // width of the bed bounding box
     Vec2f m_bed_bottom_left; // bottom-left corner coordinates (for rectangular beds)
 
+    float m_first_layer_flow_ratio;
 	float m_perimeter_width = 0.4f * Width_To_Nozzle_Ratio; // Width of an extrusion line, also a perimeter spacing for 100% infill.
     float m_nozzle_change_perimeter_width = 0.4f * Width_To_Nozzle_Ratio;
 	float m_extrusion_flow = 0.038f; //0.029f;// Extrusion flow is derived from m_perimeter_width, layer height and filament diameter.
-
+    std::unordered_map<int, std::pair<float,float>> m_block_infill_gap_width; // categories to infill_gap: toolchange gap, nozzlechange gap
 	// Extruder specific parameters.
     std::vector<FilamentParameters> m_filpar;
 
@@ -528,50 +528,52 @@ private:
 	// A fill-in direction (positive Y, negative Y) alternates with each layer.
 	wipe_shape   	m_current_shape = SHAPE_NORMAL;
     size_t 	m_current_tool  = 0;
-	// Orca: support mmu wipe tower
-    std::vector<std::vector<float>> wipe_volumes;
+	// BBS
+    //const std::vector<std::vector<float>> wipe_volumes;
 
 	float           m_depth_traversed = 0.f; // Current y position at the wipe tower.
     bool            m_current_layer_finished = false;
 	bool 			m_left_to_right   = true;
 	float			m_extra_spacing   = 1.f;
 	float           m_tpu_fixed_spacing = 2;
-    std::vector<Vec2f> m_wall_skip_points;
+    float           m_max_speed = 5400.f;  // the maximum printing speed on the prime tower.
+    std::vector<std::vector<Vec2f>> m_wall_skip_points;
     std::map<float,Polylines> m_outer_wall;
+    std::vector<double>        m_printable_height;
     bool is_first_layer() const { return size_t(m_layer_info - m_plan.begin()) == m_first_layer_idx; }
+    bool                       is_valid_last_layer(int tool, int layer_id, double layer_z) const;
     bool                       m_flat_ironing=false;
-    bool                       m_enable_tower_interface_features=false;
-    bool                       m_enable_tower_interface_cooldown_during_tower=false;
-    // Filament-switcher device flag + shared printable bed for the PETG pre-extrusion offset.
-    // m_has_filament_switcher is false for the whole shipping fleet (no profile sets the key), so
-    // the PETG branch in get_next_pos never runs -> no change fleet-wide.
-    bool                       m_has_filament_switcher=false;
-    Polygons                   m_shared_print_bed;
-    bool                       m_prev_layer_had_interface=false;
-    bool                       m_current_layer_has_interface=false;
+    bool                       m_contact_ironing = false;
+    bool                       m_has_filament_switcher = false;
+    float                      m_contact_speed   = 20 * 60.f;
+    std::vector<int>           m_physical_extruder_map;
 	// Calculates length of extrusion line to extrude given volume
 	float volume_to_length(float volume, float line_width, float layer_height) const {
 		return std::max(0.f, volume / (layer_height * (line_width - layer_height * (1.f - float(M_PI) / 4.f))));
 	}
-
+    // Calculates volume of extrusion line
+    float length_to_volume(float length,float line_width, float layer_height) const
+    {
+        return std::max(0.f, length * (layer_height * (line_width - layer_height * (1.f - float(M_PI) / 4.f))));
+    }
 	// Calculates depth for all layers and propagates them downwards
 	void plan_tower();
 
 	// Goes through m_plan and recalculates depths and width of the WT to make it exactly square - experimental
 	void make_wipe_tower_square();
 
-	Vec2f get_next_pos(const WipeTower::box_coordinates &cleaning_box, float wipe_length, bool interface_layer, size_t interface_tool);
+	Vec2f get_next_pos(const WipeTower::box_coordinates &cleaning_box, float wipe_length, bool solid_toolchange);
 
     // Goes through m_plan, calculates border and finish_layer extrusions and subtracts them from last wipe
     void save_on_last_wipe();
 
 	bool is_tpu_filament(int filament_id) const;
 	bool is_petg_filament(int filament_id) const;
-    bool is_need_reverse_travel(int filament_id, bool extruder_change) const;
-
+    bool is_need_reverse_travel(int filament, bool extruder_change) const;
 	// BBS
 	box_coordinates align_perimeter(const box_coordinates& perimeter_box);
 
+    void set_for_wipe_tower_writer(WipeTowerWriter &writer);
 
     // to store information about tool changes for a given layer
 	struct WipeTowerInfo{
@@ -584,6 +586,7 @@ private:
             float wipe_volume;
 			float wipe_length;
             float nozzle_change_depth{0};
+            float nozzle_change_length{0};
 			// BBS
 			float purge_volume;
             ToolChange(size_t old, size_t newtool, float depth=0.f, float ramming_depth=0.f, float fwl=0.f, float wv=0.f, float wl = 0, float pv = 0)
@@ -613,7 +616,7 @@ private:
     // ot -1 if there is no such toolchange.
     int first_toolchange_to_nonsoluble_nonsupport(
             const std::vector<WipeTowerInfo::ToolChange>& tool_changes) const;
-
+    WipeTowerInfo::ToolChange set_toolchange(int old_tool, int new_tool, float layer_height, float wipe_volume, float purge_volume,int layer_id);
 	void toolchange_Unload(
 		WipeTowerWriter &writer,
 		const box_coordinates  &cleaning_box,
@@ -633,13 +636,10 @@ private:
 		WipeTowerWriter &writer,
 		const box_coordinates  &cleaning_box,
 		float wipe_volume);
-    void get_wall_skip_points(const WipeTowerInfo &layer);
-
-    // Per-extruder printable-height clamp (see m_printable_height). is_valid_last_layer returns
-    // false only for a multi-extruder wipe tower's final per-extruder layer that exceeds that
-    // extruder's printable height; returns true (no clamp) in every other case.
-    bool is_valid_last_layer(int tool, int layer_id, double layer_z) const;
-    void set_nozzle_last_layer_id();
+    void get_wall_skip_points(const WipeTowerInfo &layer,int layer_id);
+    void get_all_wall_skip_points();
+    ToolChangeResult merge_tcr(ToolChangeResult &first, ToolChangeResult &second);
+    float            get_block_gap_width(int tool, bool is_nozzlechangle = false);
 };
 
 

src/libslic3r/GCode/WipeTower2.cpp

@@ -24,7 +24,6 @@
 namespace Slic3r
 {
 
-static constexpr float      flat_iron_area                 = 4.f;
 constexpr float         flat_iron_speed                = 10.f * 60.f;
 static const double     wipe_tower_wall_infill_overlap = 0.0;
 static constexpr double WIPE_TOWER_RESOLUTION          = 0.1;
@@ -234,24 +233,6 @@ static Polygon rounding_rectangle(Polygon& polygon, double rounding = 2., double
     return res;
 }
 
-static std::pair<bool, Vec2f> ray_intersetion_line(const Vec2f& a, const Vec2f& v1, const Vec2f& b, const Vec2f& c)
-{
-    const Vec2f v2    = c - b;
-    double      denom = cross2(v1, v2);
-    if (fabs(denom) < EPSILON)
-        return {false, Vec2f(0, 0)};
-    const Vec2f v12    = (a - b);
-    double      nume_a = cross2(v2, v12);
-    double      nume_b = cross2(v1, v12);
-    double      t1     = nume_a / denom;
-    double      t2     = nume_b / denom;
-    if (t1 >= 0 && t2 >= 0 && t2 <= 1.) {
-        // Get the intersection point.
-        Vec2f res = a + t1 * v1;
-        return std::pair<bool, Vec2f>(true, res);
-    }
-    return std::pair<bool, Vec2f>(false, Vec2f{0, 0});
-}
 static Polygon scale_polygon(const std::vector<Vec2f>& points)
 {
     Polygon res;
@@ -296,6 +277,7 @@ static Polygon generate_rectange(const Line& line, coord_t offset)
     return poly;
 };
 
+// Straight or arc-fitted wall segment used by WipeTowerWriter2::generate_path().
 struct Segment
 {
     Vec2f      start;
@@ -306,234 +288,6 @@ struct Segment
     bool is_valid() const { return start.y() < end.y(); }
 };
 
-static std::vector<Segment> remove_points_from_segment(const Segment& segment, const std::vector<Vec2f>& skip_points, double range)
-{
-    std::vector<Segment> result;
-    result.push_back(segment);
-    float x = segment.start.x();
-
-    for (const Vec2f& point : skip_points) {
-        std::vector<Segment> newResult;
-        for (const auto& seg : result) {
-            if (point.y() + range <= seg.start.y() || point.y() - range >= seg.end.y()) {
-                newResult.push_back(seg);
-            } else {
-                if (point.y() - range > seg.start.y()) {
-                    newResult.push_back(Segment(Vec2f(x, seg.start.y()), Vec2f(x, point.y() - range)));
-                }
-                if (point.y() + range < seg.end.y()) {
-                    newResult.push_back(Segment(Vec2f(x, point.y() + range), Vec2f(x, seg.end.y())));
-                }
-            }
-        }
-
-        result = newResult;
-    }
-
-    result.erase(std::remove_if(result.begin(), result.end(), [](const Segment& seg) { return !seg.is_valid(); }), result.end());
-    return result;
-}
-
-struct IntersectionInfo
-{
-    Vec2f pos;
-    int   idx;
-    int   pair_idx; // gap_pair idx
-    float dis_from_idx;
-    bool  is_forward;
-};
-
-struct PointWithFlag
-{
-    Vec2f pos;
-    int   pair_idx; // gap_pair idx
-    bool  is_forward;
-};
-static IntersectionInfo move_point_along_polygon(
-    const std::vector<Vec2f>& points, const Vec2f& startPoint, int startIdx, float offset, bool forward, int pair_idx)
-{
-    float            remainingDistance = offset;
-    IntersectionInfo res;
-    int              mod = points.size();
-    if (forward) {
-        int next = (startIdx + 1) % mod;
-        remainingDistance -= (points[next] - startPoint).norm();
-        if (remainingDistance <= 0) {
-            res.idx          = startIdx;
-            res.pos          = startPoint + (points[next] - startPoint).normalized() * offset;
-            res.pair_idx     = pair_idx;
-            res.dis_from_idx = (points[startIdx] - res.pos).norm();
-            return res;
-        } else {
-            for (int i = (startIdx + 1) % mod; i != startIdx; i = (i + 1) % mod) {
-                float segmentLength = (points[(i + 1) % mod] - points[i]).norm();
-                if (remainingDistance <= segmentLength) {
-                    float ratio      = remainingDistance / segmentLength;
-                    res.idx          = i;
-                    res.pos          = points[i] + ratio * (points[(i + 1) % mod] - points[i]);
-                    res.dis_from_idx = remainingDistance;
-                    res.pair_idx     = pair_idx;
-                    return res;
-                }
-                remainingDistance -= segmentLength;
-            }
-            res.idx          = (startIdx - 1 + mod) % mod;
-            res.pos          = points[startIdx];
-            res.pair_idx     = pair_idx;
-            res.dis_from_idx = (res.pos - points[res.idx]).norm();
-        }
-    } else {
-        int next = (startIdx + 1) % mod;
-        remainingDistance -= (points[startIdx] - startPoint).norm();
-        if (remainingDistance <= 0) {
-            res.idx          = startIdx;
-            res.pos          = startPoint - (points[next] - points[startIdx]).normalized() * offset;
-            res.dis_from_idx = (res.pos - points[startIdx]).norm();
-            res.pair_idx     = pair_idx;
-            return res;
-        }
-        for (int i = (startIdx - 1 + mod) % mod; i != startIdx; i = (i - 1 + mod) % mod) {
-            float segmentLength = (points[(i + 1) % mod] - points[i]).norm();
-            if (remainingDistance <= segmentLength) {
-                float ratio      = remainingDistance / segmentLength;
-                res.idx          = i;
-                res.pos          = points[(i + 1) % mod] - ratio * (points[(i + 1) % mod] - points[i]);
-                res.dis_from_idx = segmentLength - remainingDistance;
-                res.pair_idx     = pair_idx;
-                return res;
-            }
-            remainingDistance -= segmentLength;
-        }
-        res.idx          = startIdx;
-        res.pos          = points[res.idx];
-        res.pair_idx     = pair_idx;
-        res.dis_from_idx = 0;
-    }
-    return res;
-};
-
-static void insert_points(std::vector<PointWithFlag>& pl, int idx, Vec2f pos, int pair_idx, bool is_forward)
-{
-    int   next = (idx + 1) % pl.size();
-    Vec2f pos1 = pl[idx].pos;
-    Vec2f pos2 = pl[next].pos;
-    if ((pos - pos1).squaredNorm() < EPSILON) {
-        pl[idx].pair_idx   = pair_idx;
-        pl[idx].is_forward = is_forward;
-    } else if ((pos - pos2).squaredNorm() < EPSILON) {
-        pl[next].pair_idx   = pair_idx;
-        pl[next].is_forward = is_forward;
-    } else {
-        pl.insert(pl.begin() + idx + 1, PointWithFlag{pos, pair_idx, is_forward});
-    }
-}
-
-static Polylines remove_points_from_polygon(
-    const Polygon& polygon, const std::vector<Vec2f>& skip_points, double range, bool is_left, Polygon& insert_skip_pg)
-{
-    assert(polygon.size() > 2);
-    Polylines                     result;
-    std::vector<PointWithFlag>    new_pl; // add intersection points for gaps, where bool indicates whether it's a gap point.
-    std::vector<IntersectionInfo> inter_info;
-    Vec2f                         ray          = is_left ? Vec2f(-1, 0) : Vec2f(1, 0);
-    auto                          polygon_box  = get_extents(polygon);
-    Point                         anchor_point = is_left ? Point{polygon_box.max[0], polygon_box.min[1]} : polygon_box.min; // rd:ld
-    std::vector<Vec2f>            points;
-    {
-        points.reserve(polygon.points.size());
-        int      idx      = polygon.closest_point_index(anchor_point);
-        Polyline tmp_poly = polygon.split_at_index(idx);
-        for (auto& p : tmp_poly)
-            points.push_back(unscale(p).cast<float>());
-        points.pop_back();
-    }
-
-    for (int i = 0; i < skip_points.size(); i++) {
-        for (int j = 0; j < points.size(); j++) {
-            Vec2f& p1                  = points[j];
-            Vec2f& p2                  = points[(j + 1) % points.size()];
-            auto [is_inter, inter_pos] = ray_intersetion_line(skip_points[i], ray, p1, p2);
-            if (is_inter) {
-                IntersectionInfo forward  = move_point_along_polygon(points, inter_pos, j, range, true, i);
-                IntersectionInfo backward = move_point_along_polygon(points, inter_pos, j, range, false, i);
-                backward.is_forward       = false;
-                forward.is_forward        = true;
-                inter_info.push_back(backward);
-                inter_info.push_back(forward);
-                break;
-            }
-        }
-    }
-
-    // insert point to new_pl
-    for (const auto& p : points)
-        new_pl.push_back({p, -1});
-    std::sort(inter_info.begin(), inter_info.end(), [](const IntersectionInfo& lhs, const IntersectionInfo& rhs) {
-        if (rhs.idx == lhs.idx)
-            return lhs.dis_from_idx < rhs.dis_from_idx;
-        return lhs.idx < rhs.idx;
-    });
-    for (int i = inter_info.size() - 1; i >= 0; i--) {
-        insert_points(new_pl, inter_info[i].idx, inter_info[i].pos, inter_info[i].pair_idx, inter_info[i].is_forward);
-    }
-
-    {
-        // set insert_pg for wipe_path
-        for (auto& p : new_pl)
-            insert_skip_pg.points.push_back(scaled(p.pos));
-    }
-
-    int      beg  = 0;
-    bool     skip = true;
-    int      i    = beg;
-    Polyline pl;
-
-    do {
-        if (skip || new_pl[i].pair_idx == -1) {
-            pl.points.push_back(scaled(new_pl[i].pos));
-            i    = (i + 1) % new_pl.size();
-            skip = false;
-        } else {
-            if (!pl.points.empty()) {
-                pl.points.push_back(scaled(new_pl[i].pos));
-                result.push_back(pl);
-                pl.points.clear();
-            }
-            int left = new_pl[i].pair_idx;
-            int j    = (i + 1) % new_pl.size();
-            while (j != beg && new_pl[j].pair_idx != left) {
-                if (new_pl[j].pair_idx != -1 && !new_pl[j].is_forward)
-                    left = new_pl[j].pair_idx;
-                j = (j + 1) % new_pl.size();
-            }
-            i    = j;
-            skip = true;
-        }
-    } while (i != beg);
-
-    if (!pl.points.empty()) {
-        if (new_pl[i].pair_idx == -1)
-            pl.points.push_back(scaled(new_pl[i].pos));
-        result.push_back(pl);
-    }
-    return result;
-}
-
-static Polylines contrust_gap_for_skip_points(
-    const Polygon& polygon, const std::vector<Vec2f>& skip_points, float wt_width, float gap_length, Polygon& insert_skip_polygon)
-{
-    if (skip_points.empty()) {
-        insert_skip_polygon = polygon;
-        return Polylines{to_polyline(polygon)};
-    }
-    bool        is_left = false;
-    const auto& pt      = skip_points.front();
-    if (abs(pt.x()) < wt_width / 2.f) {
-        is_left = true;
-    }
-    return remove_points_from_polygon(polygon, skip_points, gap_length, is_left, insert_skip_polygon);
-};
-
 static Polygon generate_rectange_polygon(const Vec2f& wt_box_min, const Vec2f& wt_box_max)
 {
     Polygon res;
@@ -1245,6 +999,12 @@ WipeTower::ToolChangeResult WipeTower2::construct_tcr(WipeTowerWriter2& writer,
 
 
 
+bool WipeTower2::use_gap_wall(const PrintConfig& config)
+{
+    // The cone wall has its own fully separate generator with no gap machinery.
+    return config.prime_tower_skip_points.value && config.wipe_tower_wall_type.value != wtwCone;
+}
+
 WipeTower2::WipeTower2(const PrintConfig& config, const PrintRegionConfig& default_region_config,int plate_idx, Vec3d plate_origin, const std::vector<std::vector<float>>& wiping_matrix, size_t initial_tool) :
     m_semm(config.single_extruder_multi_material.value),
     m_enable_filament_ramming(config.enable_filament_ramming.value),
@@ -1272,7 +1032,7 @@ WipeTower2::WipeTower2(const PrintConfig& config, const PrintRegionConfig& defau
     m_rib_width(config.wipe_tower_rib_width), 
     m_extra_rib_length(config.wipe_tower_extra_rib_length),
     m_wall_type((int)config.wipe_tower_wall_type),
-    m_flat_ironing(config.prime_tower_flat_ironing.value),
+    m_use_gap_wall(use_gap_wall(config)),
     m_enable_tower_interface_features(config.enable_tower_interface_features.value),
     m_enable_tower_interface_cooldown_during_tower(config.enable_tower_interface_cooldown_during_tower.value)
 {
@@ -1342,6 +1102,7 @@ void WipeTower2::set_extruder(size_t idx, const PrintConfig& config)
         m_filpar[idx].is_soluble = (idx != size_t(m_wipe_tower_filament - 1));
     else
         m_filpar[idx].is_soluble = config.filament_soluble.get_at(idx);
+    m_filpar[idx].is_support = config.filament_is_support.get_at(idx);
     m_filpar[idx].temperature = config.nozzle_temperature.get_at(idx);
     m_filpar[idx].first_layer_temperature = config.nozzle_temperature_initial_layer.get_at(idx);
     m_filpar[idx].filament_minimal_purge_on_wipe_tower = config.filament_minimal_purge_on_wipe_tower.get_at(idx);
@@ -1478,11 +1239,11 @@ std::vector<WipeTower::ToolChangeResult> WipeTower2::prime(
         toolchange_Load(writer, cleaning_box); // Prime the tool.
         if (idx_tool + 1 == tools.size()) {
             // Last tool should not be unloaded, but it should be wiped enough to become of a pure color.
-            toolchange_Wipe(writer, cleaning_box, wipe_volumes[tools[idx_tool-1]][tool], false);
+            toolchange_Wipe(writer, cleaning_box, wipe_volumes[tools[idx_tool-1]][tool], false, true);
         } else {
             // Ram the hot material out of the melt zone, retract the filament into the cooling tubes and let it cool.
             //writer.travel(writer.x(), writer.y() + m_perimeter_width, 7200);
-            toolchange_Wipe(writer, cleaning_box , 20.f, false);
+            toolchange_Wipe(writer, cleaning_box , 20.f, false, true);
             WipeTower::box_coordinates box = cleaning_box;
             box.translate(0.f, writer.y() - cleaning_box.ld.y() + m_perimeter_width);
             toolchange_Unload(writer, box , m_filpar[m_current_tool].material, m_filpar[m_current_tool].first_layer_temperature, m_filpar[tools[idx_tool + 1]].first_layer_temperature);
@@ -1525,8 +1286,9 @@ WipeTower::ToolChangeResult WipeTower2::tool_change(size_t tool)
 
     float wipe_area = 0.f;
 	float wipe_volume = 0.f;
+    float ramming_depth = 0.f;
     bool interface_layer = m_enable_tower_interface_features && m_current_layer_has_interface;
-	
+
 	// Finds this toolchange info
 	if (tool != (unsigned int)(-1))
 	{
@@ -1534,6 +1296,7 @@ WipeTower::ToolChangeResult WipeTower2::tool_change(size_t tool)
 			if ( b.new_tool == tool ) {
                 wipe_volume = b.wipe_volume;
 				wipe_area = b.required_depth;
+                ramming_depth = b.ramming_depth;
 				break;
 			}
 	}
@@ -1571,7 +1334,9 @@ WipeTower::ToolChangeResult WipeTower2::tool_change(size_t tool)
     writer.speed_override_backup();
 	writer.speed_override(100);
 
-	Vec2f initial_position = cleaning_box.ld + Vec2f(0.f, m_depth_traversed);
+    // On a boundary wipe start this enters at the wall gap on the first wipe row;
+    // toolchange_Unload() then climbs back up to the ram band along the box interior.
+    Vec2f initial_position = toolchange_entry_pos(m_depth_traversed, ramming_depth, is_first_layer());
     writer.set_initial_position(initial_position, m_wipe_tower_width, m_wipe_tower_depth, m_internal_rotation);
 
     // Increase the extruder driver current to allow fast ramming.
@@ -1580,6 +1345,11 @@ WipeTower::ToolChangeResult WipeTower2::tool_change(size_t tool)
 
     // Ram the hot material out of the melt zone, retract the filament into the cooling tubes and let it cool.
     if (tool != (unsigned int)-1){ 			// This is not the last change.
+        // Without a ram — or with the boundary wipe start, where the ram band is
+        // quantized to whole rows — the box is planned as whole wipe rows; the wipe
+        // then fills it completely so adjacent purge blocks stay contiguous. Uses the
+        // old tool (m_current_tool before toolchange_Change).
+        const bool fill_box = !tool_ramming_enabled(m_current_tool) || boundary_wipe_start_enabled(m_current_tool);
         auto new_tool_temp = is_first_layer() ? m_filpar[tool].first_layer_temperature : m_filpar[tool].temperature;
         toolchange_Unload(writer, cleaning_box, m_filpar[m_current_tool].material,
                           (is_first_layer() ? m_filpar[m_current_tool].first_layer_temperature : m_filpar[m_current_tool].temperature),
@@ -1602,7 +1372,7 @@ WipeTower::ToolChangeResult WipeTower2::tool_change(size_t tool)
                 writer.extrude_explicit(target_x, writer.y(), pre_len, 600.f);
             }
         }
-        toolchange_Wipe(writer, cleaning_box, wipe_volume, interface_layer);     // Wipe the newly loaded filament until the end of the assigned wipe area.
+        toolchange_Wipe(writer, cleaning_box, wipe_volume, interface_layer, false, fill_box);     // Wipe the newly loaded filament until the end of the assigned wipe area.
         if (interface_layer) {
             int interface_temp = m_filpar[tool].interface_print_temperature;
             if (!m_enable_tower_interface_cooldown_during_tower && interface_temp > 0 && interface_temp != base_temp)
@@ -1657,11 +1427,20 @@ void WipeTower2::toolchange_Unload(
 	float remaining = xr - xl ;							// keeps track of distance to the next turnaround
 	float e_done = 0;									// measures E move done from each segment   
 
-    // Orca: Do ramming when SEMM and ramming is enabled or when multi tool head when ramming is enabled on the multi tool.
-    const bool do_ramming = (m_semm && m_enable_filament_ramming) || m_filpar[m_current_tool].multitool_ramming;
+    const bool do_ramming = tool_ramming_enabled(m_current_tool);
     const bool cold_ramming = m_is_mk4mmu3;
+    // Orca: see set_toolchange() — quantized ram band + wipe restart at the boundary.
+    const bool boundary_wipe_start = boundary_wipe_start_enabled(m_current_tool);
+    float planned_ramming_depth = 0.f;
+    if (boundary_wipe_start && m_layer_info != m_plan.end())
+        for (const auto& tch : m_layer_info->tool_changes)
+            if (tch.old_tool == m_current_tool) { planned_ramming_depth = tch.ramming_depth; break; }
 
     if (do_ramming) {
+        if (boundary_wipe_start)
+            // The entry sits at the wall gap on the first wipe row past the reserved
+            // ram band; step inward first, then move to the band clear of the wall.
+            writer.travel(Vec2f(ramming_start_pos.x(), writer.y()));
         writer.travel(ramming_start_pos); // move to starting position
         if (! m_is_mk4mmu3)
             writer.disable_linear_advance();
@@ -1672,7 +1451,8 @@ void WipeTower2::toolchange_Unload(
         writer.set_position(ramming_start_pos);
 
     // if the ending point of the ram would end up in mid air, align it with the end of the wipe tower:
-    if (do_ramming && (m_layer_info > m_plan.begin() && m_layer_info < m_plan.end() && (m_layer_info-1!=m_plan.begin() || !m_adhesion ))) {
+    // (with a boundary wipe start the band is quantized to whole rows below, so no phase alignment is needed)
+    if (do_ramming && !boundary_wipe_start && (m_layer_info > m_plan.begin() && m_layer_info < m_plan.end() && (m_layer_info-1!=m_plan.begin() || !m_adhesion ))) {
 
         // this is y of the center of previous sparse infill border
         float sparse_beginning_y = 0.f;
@@ -1731,6 +1511,28 @@ void WipeTower2::toolchange_Unload(
 			e_done = 0;
 		}
 	}
+
+    // Orca: quantize the ram band up to the whole reserved rows (BBL quantizes the
+    // old-tool purge the same way) so no unprinted void is left between the band and
+    // the wipe restarting at the boundary below it.
+    if (planned_ramming_depth > 0.f) {
+        const int   reserved_rows = std::max(1, int(std::round(planned_ramming_depth / y_step)));
+        const float last_row_y    = ramming_start_pos.y() + (reserved_rows - 1) * y_step;
+        // Same bead model as the ramming segments above: E per mm of ram line.
+        const float e_per_mm      = 1.f / (volume_to_length(1.f, line_width, m_layer_height) * filament_area());
+        const float fill_feed     = m_filpar[m_current_tool].ramming_speed.empty() ? 3000.f :
+            60.f * volume_to_length(m_filpar[m_current_tool].ramming_speed.back(), line_width, m_layer_height);
+        while (true) {
+            const float target_x = m_left_to_right ? xr : xl;
+            if (std::abs(target_x - writer.x()) > WT_EPSILON)
+                writer.ram(writer.x(), target_x, 0.f, 0.f, e_per_mm * std::abs(target_x - writer.x()), fill_feed);
+            if (writer.y() + 0.5f * y_step > last_row_y)
+                break;
+            writer.travel(writer.x(), writer.y() + y_step, 7200);
+            m_left_to_right = !m_left_to_right;
+        }
+    }
+
 	Vec2f end_of_ramming(writer.x(),writer.y());
     writer.change_analyzer_line_width(m_perimeter_width);   // so the next lines are not affected by ramming_line_width_multiplier
 
@@ -1838,10 +1640,27 @@ void WipeTower2::toolchange_Unload(
     // this is to align ramming and future wiping extrusions, so the future y-steps can be uniform from the start:
     // the perimeter_width will later be subtracted, it is there to not load while moving over just extruded material
     Vec2f pos = Vec2f(end_of_ramming.x(), end_of_ramming.y() + (y_step/m_extra_spacing_ramming-m_perimeter_width) / 2.f + m_perimeter_width);
-    if (do_ramming)
+    if (planned_ramming_depth > 0.f) {
+        // Orca: restart the wipe at the left-edge boundary on a fresh row below the
+        // quantized ram band so the entry scrub always runs at the wall gap (BBL keeps
+        // CP_TOOLCHANGE_WIPE starting at a box corner the same way). Same lattice
+        // formula as the no-ram branch below, offset by the ram band.
+        writer.travel(Vec2f(ramming_start_pos.x(),
+            cleaning_box.ld.y() + m_depth_traversed +
+                wipe_start_offset_after_ram(planned_ramming_depth, is_first_layer()) + m_perimeter_width), 2400.f);
+        m_left_to_right = true;
+    }
+    else if (do_ramming)
         writer.travel(pos, 2400.f);
-    else
-        writer.set_position(pos);
+    else {
+        // Orca: with no ram printed there is no ramming geometry to align with. Start the
+        // first wipe row so the purge row lattice continues across the block boundary
+        // (previous box's last row top edge sits at its box top): with the planned depth
+        // of rows * dy, the last row's top edge then lands exactly on this box's top and
+        // no blank band is left between adjacent purge blocks.
+        writer.set_position(Vec2f(end_of_ramming.x(),
+            cleaning_box.ld.y() + m_depth_traversed + wipe_start_offset_after_ram(0.f, is_first_layer()) + m_perimeter_width));
+    }
 
     writer.resume_preview()
           .flush_planner_queue();
@@ -1920,7 +1739,9 @@ void WipeTower2::toolchange_Wipe(
 	WipeTowerWriter2 &writer,
 	const WipeTower::box_coordinates  &cleaning_box,
 	float wipe_volume,
-    bool interface_layer)
+    bool interface_layer,
+    bool priming,
+    bool fill_box)
 {
 	// Increase flow on first layer, slow down print.
     writer.set_extrusion_flow(m_extrusion_flow * (is_first_layer() ? 1.18f : 1.f))
@@ -1929,7 +1750,7 @@ void WipeTower2::toolchange_Wipe(
 	const float& xr = cleaning_box.rd.x();
 
     writer.set_extrusion_flow(m_extrusion_flow * m_extra_flow);
-    const float line_width = m_perimeter_width * m_extra_flow;
+    const float line_width = wipe_line_width();
     writer.change_analyzer_line_width(line_width);
 
 	// Variables x_to_wipe and traversed_x are here to be able to make sure it always wipes at least
@@ -1937,7 +1758,7 @@ void WipeTower2::toolchange_Wipe(
     // wipe until the end of the assigned area.
 
 	float x_to_wipe = volume_to_length(wipe_volume, m_perimeter_width, m_layer_height) / m_extra_flow;
-	float dy = (is_first_layer() ? m_extra_flow : m_extra_spacing_wipe) * m_perimeter_width; // Don't use the extra spacing for the first layer, but do use the spacing resulting from increased flow.
+	float dy = wipe_row_spacing(is_first_layer()); // Don't use the extra spacing for the first layer, but do use the spacing resulting from increased flow.
     // All the calculations in all other places take the spacing into account for all the layers.
 
 	// If spare layers are excluded->if 1 or less toolchange has been done, it must be sill the first layer, too.So slow down.
@@ -1950,9 +1771,6 @@ void WipeTower2::toolchange_Wipe(
         m_left_to_right = !m_left_to_right;
     }
     
-    const bool do_ironing = m_flat_ironing && (!interface_layer || !m_enable_tower_interface_features);
-    const float ironing_area = m_filpar[m_current_tool].tower_ironing_area;
-
     // now the wiping itself:
 	for (int i = 0; true; ++i)	{
 		if (i!=0) {
@@ -1963,22 +1781,45 @@ void WipeTower2::toolchange_Wipe(
 		}
 
 		float traversed_x = writer.x();
+
+        // BBS gap wall: iron the first few mm of the purge, then drag the retracted nozzle
+        // back out through the wall gap and scrub it with a dry spiral centred on the entry
+        // point so the toolchange start blob is not left on the wall (same sequence as the
+        // BBL tower's toolchange_wipe_new; the spiral self-disables when the filament's
+        // tower ironing area is 0). WT2's entry gap always sits at the left-edge entry
+        // point, so only iron when the purge actually starts there heading right (in-place
+        // toolchangers do; SEMM ram/cooling moves leave the nozzle mid-box, far from any gap).
+        if (i == 0 && m_use_gap_wall && !interface_layer && !priming && m_left_to_right &&
+            writer.x() - xl < 2.5f * line_width) {
+            float ironing_length = 3.f;
+            if (xr - writer.x() < ironing_length)
+                ironing_length = std::max(xr - writer.x(), 0.f);
+            const float retract_length = m_filpar[m_current_tool].retract_length;
+            const float retract_speed  = m_filpar[m_current_tool].retract_speed * 60.f;
+            writer.extrude(writer.x() + ironing_length, writer.y(), wipe_speed);
+            writer.retract(retract_length, retract_speed);
+            writer.travel(writer.x() - 1.5f * ironing_length, writer.y(), 600.f);
+            writer.travel(writer.x() + 0.5f * ironing_length, writer.y(), 240.f);
+            const Vec2f iron_end(writer.x() + ironing_length, writer.y());
+            writer.spiral_flat_ironing(writer.pos(), m_filpar[m_current_tool].tower_ironing_area, m_perimeter_width, flat_iron_speed);
+            writer.travel(iron_end, wipe_speed);
+            writer.retract(-retract_length, retract_speed);
+        }
+
 		if (m_left_to_right)
             writer.extrude(xr - (i % 4 == 0 ? 0 : 1.5f*line_width), writer.y(), wipe_speed);
 		else
             writer.extrude(xl + (i % 4 == 1 ? 0 : 1.5f*line_width), writer.y(), wipe_speed);
 
-        if (i == 0 && do_ironing && ironing_area > 0.f) {
-            writer.travel(writer.x(), writer.y(), 600.f);
-            writer.spiral_flat_ironing(writer.pos(), ironing_area, m_perimeter_width, 10.f * 60.f);
-        }
-
         if (writer.y()+float(EPSILON) > cleaning_box.lu.y()-0.5f*line_width)
             break;		// in case next line would not fit
 
 		traversed_x -= writer.x();
         x_to_wipe -= std::abs(traversed_x);
-		if (x_to_wipe < WT_EPSILON) {
+        // Orca: with no ram printed the box was planned as whole wipe rows; fill it
+        // completely (quantizing the purge up to the planned rows) so the next block
+        // can start right above it without a blank band in between.
+        if (!fill_box && x_to_wipe < WT_EPSILON) {
             writer.travel(m_left_to_right ? xl + 1.5f*line_width : xr - 1.5f*line_width, writer.y(), 7200);
 			break;
 		}
@@ -2110,7 +1951,7 @@ WipeTower::ToolChangeResult WipeTower2::finish_layer()
         poly = generate_support_cone_wall(writer, wt_box, feedrate, infill_cone, spacing);
     } else {
         WipeTower::box_coordinates wt_box(Vec2f(0.f, 0.f), m_wipe_tower_width, m_layer_info->depth + m_perimeter_width);
-        poly = generate_support_rib_wall(writer, wt_box, feedrate, first_layer, m_wall_type == (int)wtwRib, true, false);
+        poly = generate_support_rib_wall(writer, wt_box, feedrate, first_layer, m_wall_type == (int)wtwRib, true);
     }
 
     // brim (first layer only)
@@ -2228,15 +2069,32 @@ void WipeTower2::plan_toolchange(float z_par, float layer_height_par, unsigned i
         return;
 
     // this is an actual toolchange - let's calculate depth to reserve on the wipe tower
-    float width = m_wipe_tower_width - 3*m_perimeter_width; 
-	float length_to_extrude = volume_to_length(0.25f * std::accumulate(m_filpar[old_tool].ramming_speed.begin(), m_filpar[old_tool].ramming_speed.end(), 0.f),
-										m_perimeter_width * m_filpar[old_tool].ramming_line_width_multiplicator,
-										layer_height_par);
-    // Orca: Set ramming depth to 0 if ramming is disabled.
-    float ramming_depth = m_enable_filament_ramming ? ((int(length_to_extrude / width) + 1) * (m_perimeter_width * m_filpar[old_tool].ramming_line_width_multiplicator * m_filpar[old_tool].ramming_step_multiplicator) * m_extra_spacing_ramming) : 0;
-    float first_wipe_line = - (width*((length_to_extrude / width)-int(length_to_extrude / width)) - width);
+    const bool first_layer_plan = (m_plan.size() - 1) == m_first_layer_idx;
+    m_plan.back().tool_changes.push_back(set_toolchange(old_tool, new_tool, layer_height_par, wipe_volume, first_layer_plan));
+}
 
-    float first_wipe_volume = length_to_volume(first_wipe_line, m_perimeter_width * m_extra_flow, layer_height_par);
+WipeTower2::WipeTowerInfo::ToolChange WipeTower2::set_toolchange(size_t old_tool, size_t new_tool, float layer_height, float wipe_volume, bool first_layer_plan)
+{
+    float width = m_wipe_tower_width - 3*m_perimeter_width;
+	float length_to_extrude = volume_to_length((m_semm ? 0.25f : m_filpar[old_tool].multitool_ramming_time) * std::accumulate(m_filpar[old_tool].ramming_speed.begin(), m_filpar[old_tool].ramming_speed.end(), 0.f),
+										m_perimeter_width * m_filpar[old_tool].ramming_line_width_multiplicator,
+										layer_height);
+    // Orca: Reserve ramming depth only when toolchange_Unload() will actually ram,
+    // otherwise the unprinted reservation leaves blank bands between the purge boxes.
+    const bool do_ramming = tool_ramming_enabled(old_tool);
+    // Orca: with the gap wall on a multi-tool printer the ram band is quantized up to
+    // the whole reserved rows and the wipe restarts at the left-edge boundary on a
+    // fresh row below it (BBL parity: the old-tool purge is whole rows and the wipe
+    // always starts at the box corner, where the entry scrub runs).
+    const bool boundary_wipe_start = boundary_wipe_start_enabled(old_tool);
+    float ramming_depth = do_ramming ? ((int(length_to_extrude / width) + 1) * (m_perimeter_width * m_filpar[old_tool].ramming_line_width_multiplicator * m_filpar[old_tool].ramming_step_multiplicator) * m_extra_spacing_ramming) : 0;
+    // first_wipe_line rides for free on the last (partially used) ramming row, which
+    // is already covered by ramming_depth. Without ramming that row does not exist
+    // (and with a boundary wipe start the ram band is quantized to whole rows), so
+    // the whole wipe volume needs reserved wiping depth.
+    float first_wipe_line = (do_ramming && !boundary_wipe_start) ? - (width*((length_to_extrude / width)-int(length_to_extrude / width)) - width) : 0.f;
+
+    float first_wipe_volume = length_to_volume(first_wipe_line, m_perimeter_width * m_extra_flow, layer_height);
 
     // ORCA: Keep wipe-depth planning consistent with toolchange_Wipe().
     // ORCA: On the first layer, toolchange_Wipe() advances purge rows using
@@ -2245,12 +2103,11 @@ void WipeTower2::plan_toolchange(float z_par, float layer_height_par, unsigned i
     // ORCA: float dy = (is_first_layer() ? m_extra_flow : m_extra_spacing_wipe) * m_perimeter_width;
     // ORCA: Use the same spacing here so reserved depth matches consumed depth
     // ORCA: and first-layer purge segments do not leave visible gaps.
-    const bool first_layer_plan = (m_plan.size() - 1) == m_first_layer_idx;
     const float planning_spacing = first_layer_plan ? m_extra_flow : m_extra_spacing_wipe;
 
-    float wiping_depth = get_wipe_depth(wipe_volume - first_wipe_volume, layer_height_par, m_perimeter_width, m_extra_flow, planning_spacing, width);
-    
-	m_plan.back().tool_changes.push_back(WipeTowerInfo::ToolChange(old_tool, new_tool, ramming_depth + wiping_depth, ramming_depth, first_wipe_line, wipe_volume));
+    float wiping_depth = get_wipe_depth(wipe_volume - first_wipe_volume, layer_height, m_perimeter_width, m_extra_flow, planning_spacing, width);
+
+	return WipeTowerInfo::ToolChange(old_tool, new_tool, ramming_depth + wiping_depth, ramming_depth, first_wipe_line, wipe_volume);
 }
 
 
@@ -2288,49 +2145,64 @@ void WipeTower2::save_on_last_wipe()
             continue;
 
         // Which toolchange will finish_layer extrusions be subtracted from?
-        int idx = first_toolchange_to_nonsoluble(m_layer_info->tool_changes);
+        int idx = first_toolchange_to_nonsoluble_nonsupport(m_layer_info->tool_changes);
 
         if (idx == -1) {
             // In this case, finish_layer will be called at the very beginning.
             finish_layer().total_extrusion_length_in_plane();
         }
 
+        const float width = m_wipe_tower_width - 3*m_perimeter_width; // width we draw into
+        auto recompute_toolchange = [this, width](WipeTowerInfo::ToolChange& toolchange, float volume_to_save) {
+            float volume_left_to_wipe = std::max(m_filpar[toolchange.new_tool].filament_minimal_purge_on_wipe_tower, toolchange.wipe_volume_total - volume_to_save);
+            float volume_we_need_depth_for = std::max(0.f, volume_left_to_wipe - length_to_volume(toolchange.first_wipe_line, m_perimeter_width*m_extra_flow, m_layer_info->height));
+
+            // ORCA: Keep wipe-depth planning consistent with toolchange_Wipe().
+            // ORCA: On the first layer, toolchange_Wipe() advances purge rows using
+            // ORCA: m_extra_flow * m_perimeter_width, while later layers use
+            // ORCA: m_extra_spacing_wipe * m_perimeter_width.
+            // ORCA: float dy = (is_first_layer() ? m_extra_flow : m_extra_spacing_wipe) * m_perimeter_width;
+            // ORCA: Use the same spacing here so reserved depth matches consumed depth
+            // ORCA: and first-layer purge segments do not leave visible gaps.
+            const bool first_layer_plan = size_t(m_layer_info - m_plan.begin()) == m_first_layer_idx;
+            const float planning_spacing = first_layer_plan ? m_extra_flow : m_extra_spacing_wipe;
+
+            float depth_to_wipe = get_wipe_depth(volume_we_need_depth_for, m_layer_info->height, m_perimeter_width, m_extra_flow, planning_spacing, width);
+
+            toolchange.required_depth = toolchange.ramming_depth + depth_to_wipe;
+            toolchange.wipe_volume = volume_left_to_wipe;
+        };
+
         for (int i=0; i<int(m_layer_info->tool_changes.size()); ++i) {
             auto& toolchange = m_layer_info->tool_changes[i];
             tool_change(toolchange.new_tool);
 
             if (i == idx) {
-                float width = m_wipe_tower_width - 3*m_perimeter_width; // width we draw into
-
-                float volume_to_save = length_to_volume(finish_layer().total_extrusion_length_in_plane(), m_perimeter_width, m_layer_info->height);
-                float volume_left_to_wipe = std::max(m_filpar[toolchange.new_tool].filament_minimal_purge_on_wipe_tower, toolchange.wipe_volume_total - volume_to_save);
-                float volume_we_need_depth_for = std::max(0.f, volume_left_to_wipe - length_to_volume(toolchange.first_wipe_line, m_perimeter_width*m_extra_flow, m_layer_info->height));
-                
-                // ORCA: Keep wipe-depth planning consistent with toolchange_Wipe().
-                // ORCA: On the first layer, toolchange_Wipe() advances purge rows using
-                // ORCA: m_extra_flow * m_perimeter_width, while later layers use
-                // ORCA: m_extra_spacing_wipe * m_perimeter_width.
-                // ORCA: float dy = (is_first_layer() ? m_extra_flow : m_extra_spacing_wipe) * m_perimeter_width;
-                // ORCA: Use the same spacing here so reserved depth matches consumed depth
-                // ORCA: and first-layer purge segments do not leave visible gaps.
-                const bool first_layer_plan = size_t(m_layer_info - m_plan.begin()) == m_first_layer_idx;
-                const float planning_spacing = first_layer_plan ? m_extra_flow : m_extra_spacing_wipe;
-                
-                float depth_to_wipe = get_wipe_depth(volume_we_need_depth_for, m_layer_info->height, m_perimeter_width, m_extra_flow, planning_spacing, width);
-
-                toolchange.required_depth = toolchange.ramming_depth + depth_to_wipe;
-                toolchange.wipe_volume = volume_left_to_wipe;
+                recompute_toolchange(toolchange, length_to_volume(finish_layer().total_extrusion_length_in_plane(), m_perimeter_width, m_layer_info->height));
+            } else if (toolchange.wipe_volume < m_filpar[toolchange.new_tool].filament_minimal_purge_on_wipe_tower) {
+                // Keep filament_minimal_purge_on_wipe_tower enforced for toolchanges that get
+                // no finish-layer saving, e.g. a support/soluble filament skipped as the
+                // finish filament above. Recomputing only when the clamp binds leaves all
+                // other toolchanges with their planned values bit-for-bit.
+                recompute_toolchange(toolchange, 0.f);
             }
         }
     }
 }
 
 
-// Return index of first toolchange that switches to non-soluble extruder
-// ot -1 if there is no such toolchange.
-int WipeTower2::first_toolchange_to_nonsoluble(
+// Return the index of the toolchange whose new filament should print the layer's
+// finish extrusions (sparse infill + wall + brim), or -1 to print them with the
+// layer's incoming filament before any toolchange happens.
+// Like WipeTower::first_toolchange_to_nonsoluble_nonsupport(): support and soluble
+// filaments bond poorly to the material printed on top of them, so they must not
+// print the tower's shell when another filament is available on the layer.
+int WipeTower2::first_toolchange_to_nonsoluble_nonsupport(
         const std::vector<WipeTowerInfo::ToolChange>& tool_changes) const
 {
+    if (tool_changes.empty())
+        return -1;
+
     // If a specific wipe tower filament is forced, use it to decide where to finish the layer.
     if (m_wipe_tower_filament > 0) {
         for (size_t idx = 0; idx < tool_changes.size(); ++idx) {
@@ -2339,8 +2211,19 @@ int WipeTower2::first_toolchange_to_nonsoluble(
         }
         return -1;
     }
-    // Orca: allow calculation of the required depth and wipe volume for soluble toolchanges as well.
-    return tool_changes.empty() ? -1 : 0;
+
+    auto is_wall_filament = [this](size_t tool) {
+        return !m_filpar[tool].is_soluble && !m_filpar[tool].is_support;
+    };
+    for (size_t idx = 0; idx < tool_changes.size(); ++idx)
+        if (is_wall_filament(tool_changes[idx].new_tool))
+            return idx;
+    if (is_wall_filament(tool_changes.front().old_tool))
+        return -1;
+    // Only support/soluble filaments on this layer: keep the first toolchange so the
+    // finish-layer saving and the minimal-purge clamp still apply to it (Orca depth
+    // and wipe volume accounting, see save_on_last_wipe()).
+    return 0;
 }
 
 static WipeTower::ToolChangeResult merge_tcr(WipeTower::ToolChangeResult& first,
@@ -2363,6 +2246,24 @@ static WipeTower::ToolChangeResult merge_tcr(WipeTower::ToolChangeResult& first,
 }
 
 
+// Precompute, for every plan layer, the wall openings ("skip points") at each toolchange's
+// entry position, like WipeTower::get_all_wall_skip_points(). toolchange_entry_pos()
+// reproduces from the finalized plan where tool_change() will start, so each gap coincides
+// with the entry travel's target (tcr.start_pos, pre-rotation frame). BBL parity: the gap
+// sits at the CP_TOOLCHANGE_WIPE start row, never at the ram band.
+void WipeTower2::compute_wall_skip_points()
+{
+    m_wall_skip_points.assign(m_plan.size(), std::vector<Vec2f>());
+    for (size_t layer_id = 0; layer_id < m_plan.size(); ++layer_id) {
+        float depth_traversed = 0.f;
+        for (const auto& toolchange : m_plan[layer_id].tool_changes) {
+            m_wall_skip_points[layer_id].emplace_back(
+                toolchange_entry_pos(depth_traversed, toolchange.ramming_depth, layer_id == m_first_layer_idx));
+            depth_traversed += toolchange.required_depth;
+        }
+    }
+}
+
 // Processes vector m_plan and calls respective functions to generate G-code for the wipe tower
 // Resulting ToolChangeResults are appended into vector "result"
 void WipeTower2::generate(std::vector<std::vector<WipeTower::ToolChangeResult>> &result)
@@ -2378,12 +2279,41 @@ void WipeTower2::generate(std::vector<std::vector<WipeTower::ToolChangeResult>>
     }
 #endif
 
-    m_rib_length = std::max({m_rib_length, sqrt(m_wipe_tower_depth * m_wipe_tower_depth + m_wipe_tower_width * m_wipe_tower_width)});
+    if (m_wall_type == (int)wtwRib) {
+        // Rib wall: force a square tower like WipeTower::plan_tower_new(), ignoring the
+        // configured prime_tower_width (the GUI greys it out in rib mode). The planned depths
+        // already include the extra-spacing factors, so sqrt(depth * width) preserves the
+        // purge area. Replan every toolchange for the new width, then re-derive the depths.
+        float max_depth = 0.f;
+        for (const auto& current_plan : m_plan)
+            max_depth = std::max(max_depth, current_plan.depth);
+        if (max_depth > EPSILON) {
+            m_wipe_tower_width = align_ceil(std::sqrt(max_depth * m_wipe_tower_width), m_perimeter_width);
+            for (size_t idx = 0; idx < m_plan.size(); ++idx)
+                for (auto& toolchange : m_plan[idx].tool_changes)
+                    toolchange = set_toolchange(toolchange.old_tool, toolchange.new_tool,
+                                                m_plan[idx].height, toolchange.wipe_volume,
+                                                idx == m_first_layer_idx);
+            plan_tower();
+        }
+
+        // Like WipeTower::plan_tower_new(): extend the ribs instead of the tower when the
+        // tower is smaller than the height-based stability minimum.
+        const float min_depth = WipeTower::get_limit_depth_by_height(m_wipe_tower_height);
+        if (m_wipe_tower_depth + EPSILON < min_depth)
+            m_rib_length = std::max(m_rib_length, min_depth * (float)std::sqrt(2.f));
+    }
+
+    const float diagonal = std::sqrt(m_wipe_tower_depth * m_wipe_tower_depth + m_wipe_tower_width * m_wipe_tower_width);
+    m_rib_length = std::max(m_rib_length, diagonal);
     m_rib_length += m_extra_rib_length;
-    m_rib_length = std::max(0.f, m_rib_length);
+    m_rib_length = std::max(diagonal, m_rib_length); // a negative extra length must not shrink the ribs below the diagonal
     m_rib_width  = std::min(m_rib_width, std::min(m_wipe_tower_depth, m_wipe_tower_width) /
                                              2.f); // Ensure that the rib wall of the wipetower are attached to the infill.
 
+    if (m_use_gap_wall)
+        compute_wall_skip_points();
+
     m_layer_info = m_plan.begin();
     m_current_height = 0.f;
 
@@ -2410,7 +2340,7 @@ void WipeTower2::generate(std::vector<std::vector<WipeTower::ToolChangeResult>>
         if (m_layer_info->depth < m_wipe_tower_depth - m_perimeter_width)
 			m_y_shift = (m_wipe_tower_depth-m_layer_info->depth-m_perimeter_width)/2.f;
 
-        int idx = first_toolchange_to_nonsoluble(layer.tool_changes);
+        int idx = first_toolchange_to_nonsoluble_nonsupport(layer.tool_changes);
         WipeTower::ToolChangeResult finish_layer_tcr;
 
         if (idx == -1) {
@@ -2503,8 +2433,7 @@ Polygon WipeTower2::generate_support_rib_wall(WipeTowerWriter2&
                                              double                 feedrate,
                                              bool                   first_layer,
                                              bool                   rib_wall,
-                                             bool                   extrude_perimeter,
-                                             bool                   skip_points)
+                                             bool                   extrude_perimeter)
 {
 
     float     retract_length = m_filpar[m_current_tool].retract_length;
@@ -2524,18 +2453,28 @@ Polygon WipeTower2::generate_support_rib_wall(WipeTowerWriter2&
     if (!extrude_perimeter)
         return wall_polygon;
 
-    if (skip_points) {
-        result_wall = contrust_gap_for_skip_points(wall_polygon, std::vector<Vec2f>(), m_wipe_tower_width, 2.5 * m_perimeter_width,
+    if (m_use_gap_wall) {
+        // Cut the wall open at each toolchange's entry (see compute_wall_skip_points()).
+        // The vector is empty during the save_on_last_wipe planning passes, which therefore
+        // measure the un-gapped wall — same approximation as the BBL tower.
+        static const std::vector<Vec2f> no_skip_points;
+        const size_t layer_id = size_t(m_layer_info - m_plan.begin());
+        const std::vector<Vec2f>& layer_skip_points =
+            layer_id < m_wall_skip_points.size() ? m_wall_skip_points[layer_id] : no_skip_points;
+        result_wall = contrust_gap_for_skip_points(wall_polygon, layer_skip_points, m_wipe_tower_width, 2.5 * m_perimeter_width,
                                                    insert_skip_polygon);
     } else {
         result_wall.push_back(to_polyline(wall_polygon));
         insert_skip_polygon = wall_polygon;
     }
     writer.generate_path(result_wall, feedrate, retract_length, retract_speed, m_used_fillet);
-    //if (m_cur_layer_id == 0) {
-    //    BoundingBox bbox = get_extents(result_wall);
-    //    m_rib_offset     = Vec2f(-unscaled<float>(bbox.min.x()), -unscaled<float>(bbox.min.y()));
-    //}
+    // Tower-local shift that puts the rib wall's protruding first-layer min corner at the
+    // configured tower position, like WipeTower::generate_support_wall_new(). Measured on
+    // the un-gapped outline so a wall gap cannot shift the tower.
+    if (rib_wall && is_first_layer()) {
+        BoundingBox bbox = get_extents(insert_skip_polygon);
+        m_rib_offset     = Vec2f(-unscaled<float>(bbox.min.x()), -unscaled<float>(bbox.min.y()));
+    }
 
     return insert_skip_polygon;
 }

src/libslic3r/GCode/WipeTower2.hpp

@@ -34,6 +34,10 @@ public:
 								   bool is_finish,
                                    bool is_contact = false) const;
 
+    // Whether this print cuts wall openings ("skip points") at the toolchange entries.
+    // Shared with the entry routing in GCode.cpp so the router and the tower agree.
+    static bool use_gap_wall(const PrintConfig& config);
+
 	// x			-- x coordinates of wipe tower in mm ( left bottom corner )
 	// y			-- y coordinates of wipe tower in mm ( left bottom corner )
 	// width		-- width of wipe tower in mm ( default 60 mm - leave as it is )
@@ -69,9 +73,9 @@ public:
         const float brim = m_wipe_tower_brim_width_real;
         return BoundingBoxf(Vec2d(-brim, -brim), Vec2d(double(m_wipe_tower_width) + brim, double(m_wipe_tower_depth) + brim));
     }
-    // WT2 doesn't currently compute a rib-origin compensation like WipeTower (m_rib_offset),
-    // so expose a zero offset for consistency purposes (to maintain API parity).
-    Vec2f get_rib_offset() const { return Vec2f::Zero(); }
+    // Tower-local shift that puts the rib wall's first-layer min corner at the configured
+    // tower position, like WipeTower::get_rib_offset(). Zero unless the rib wall is used.
+    Vec2f get_rib_offset() const { return m_rib_offset; }
     float get_rib_width() const { return m_rib_width; }
     float get_rib_length() const { return m_rib_length; }
 
@@ -149,6 +153,7 @@ public:
     struct FilamentParameters {
         std::string 	    material = "PLA";
         bool                is_soluble = false;
+        bool                is_support = false;
         int  			    temperature = 0;
         int  			    first_layer_temperature = 0;
         int                 interface_print_temperature = 0;
@@ -220,7 +225,6 @@ private:
 	float  m_perimeter_speed    = 0.f;
     float  m_first_layer_speed  = 0.f;
     size_t m_first_layer_idx    = size_t(-1);
-    bool   m_flat_ironing       = false;
     bool   m_enable_tower_interface_features = false;
     bool   m_enable_tower_interface_cooldown_during_tower = false;
     bool   m_prev_layer_had_interface = false;
@@ -231,6 +235,12 @@ private:
     float  m_rib_width                    = 10;
     float  m_extra_rib_length             = 0;
     float  m_rib_length                   = 0;
+    Vec2f  m_rib_offset                   = Vec2f::Zero();
+    bool   m_use_gap_wall                 = false;
+    // Per plan layer, each toolchange's entry position (tower-local, un-shifted frame):
+    // where the wall is cut open so the entry travel does not cross the printed wall.
+    // Filled by compute_wall_skip_points() once the plan is final.
+    std::vector<std::vector<Vec2f>> m_wall_skip_points;
 
     bool   m_enable_arc_fitting           = false;
 
@@ -278,6 +288,37 @@ private:
 
     bool is_first_layer() const { return size_t(m_layer_info - m_plan.begin()) == m_first_layer_idx; }
 
+    // Purge row lattice of toolchange_Wipe(): row pitch and extrusion width.
+    float wipe_row_spacing(bool first_layer) const { return (first_layer ? m_extra_flow : m_extra_spacing_wipe) * m_perimeter_width; }
+    float wipe_line_width() const { return m_perimeter_width * m_extra_flow; }
+
+    // Whether toolchange_Unload() rams this (old) tool out.
+    bool tool_ramming_enabled(size_t tool) const { return (m_semm && m_enable_filament_ramming) || m_filpar[tool].multitool_ramming; }
+    // Whether the wipe restarts at the box boundary on a fresh row below the quantized
+    // ram band after ramming this (old) tool out (multi-tool gap wall; SEMM keeps the
+    // stock continue-from-ram-end behavior).
+    bool boundary_wipe_start_enabled(size_t tool) const { return tool_ramming_enabled(tool) && !m_semm && m_use_gap_wall; }
+
+    // With a boundary wipe start the wipe begins on a fresh row below the quantized ram
+    // band. Y offset from the box start to that first wipe row.
+    float wipe_start_offset_after_ram(float ramming_depth, bool first_layer) const
+    {
+        return ramming_depth + wipe_row_spacing(first_layer) - (m_perimeter_width + wipe_line_width()) / 2.f;
+    }
+
+    // Tower-local entry position of a toolchange whose box starts depth_traversed into
+    // the layer: the box corner, moved down to the first wipe row when the plan gives
+    // it a boundary wipe start (ramming_depth > 0 iff the unload rams). tool_change()
+    // enters here and compute_wall_skip_points() cuts the wall gap here, so the routed
+    // entry, the gap and the wipe scrub all share one opening.
+    Vec2f toolchange_entry_pos(float depth_traversed, float ramming_depth, bool first_layer) const
+    {
+        Vec2f pos(m_perimeter_width / 2.f, m_perimeter_width / 2.f + depth_traversed);
+        if (!m_semm && m_use_gap_wall && ramming_depth > 0.f)
+            pos.y() += wipe_start_offset_after_ram(ramming_depth, first_layer);
+        return pos;
+    }
+
 	// Calculates extrusion flow needed to produce required line width for given layer height
 	float extrusion_flow(float layer_height = -1.f) const	// negative layer_height - return current m_extrusion_flow
 	{
@@ -328,9 +369,10 @@ private:
     std::vector<float> m_used_filament_length;
 	std::vector<std::pair<float, std::vector<float>>> m_used_filament_length_until_layer;
 
-    // Return index of first toolchange that switches to non-soluble extruder
-    // ot -1 if there is no such toolchange.
-    int first_toolchange_to_nonsoluble(
+    // Return the index of the toolchange whose new filament should print the layer's
+    // finish extrusions (sparse infill + wall + brim), or -1 to print them with the
+    // layer's incoming filament before any toolchange happens.
+    int first_toolchange_to_nonsoluble_nonsupport(
             const std::vector<WipeTowerInfo::ToolChange>& tool_changes) const;
 
 	void toolchange_Unload(
@@ -353,7 +395,9 @@ private:
 		WipeTowerWriter2 &writer,
 		const WipeTower::box_coordinates  &cleaning_box,
 		float wipe_volume,
-        bool interface_layer);
+        bool interface_layer,
+        bool priming = false,
+        bool fill_box = false);
 
 
     Polygon generate_support_rib_wall(WipeTowerWriter2&                 writer,
@@ -361,8 +405,7 @@ private:
                                       double                 feedrate,
                                       bool                   first_layer,
                                       bool                   rib_wall,
-                                      bool                   extrude_perimeter,
-                                      bool                   skip_points);
+                                      bool                   extrude_perimeter);
 
     Polygon generate_support_cone_wall(
         WipeTowerWriter2& writer, 
@@ -372,6 +415,12 @@ private:
 		float spacing);
 
     Polygon generate_rib_polygon(const WipeTower::box_coordinates& wt_box);
+
+    void compute_wall_skip_points();
+
+    // Computes the depth reserved for a toolchange (shared by plan_toolchange() and the
+    // rib-wall square-tower replanning in generate()).
+    WipeTowerInfo::ToolChange set_toolchange(size_t old_tool, size_t new_tool, float layer_height, float wipe_volume, bool first_layer_plan);
 };
 
 

src/libslic3r/Polyline.hpp

@@ -129,13 +129,13 @@ public:
     std::vector<PathFittingData> fitting_result;
     //BBS: simplify points by arc fitting
     void simplify_by_fitting_arc(double tolerance);
-    //BBS: 
+    void reset_to_linear_move();
+    //BBS:
     Polylines equally_spaced_lines(double distance) const;
 
 private:
     void append_fitting_result_after_append_points();
     void append_fitting_result_after_append_polyline(const Polyline& src);
-    void reset_to_linear_move();
     bool split_fitting_result_before_index(const size_t index, Point &new_endpoint, std::vector<PathFittingData>& data) const;
     bool split_fitting_result_after_index(const size_t index, Point &new_startpoint, std::vector<PathFittingData>& data) const;
 };

src/libslic3r/Print.cpp

@@ -3409,7 +3409,11 @@ void Print::update_filament_maps_to_config(std::vector<int> f_maps, std::vector<
             }
             else if ((extruder_volume_type_count > extruder_count) && (m_config.filament_volume_map.values.size() > index))
                 nozzle_volume_type = (NozzleVolumeType)(m_config.filament_volume_map.values[index]);
-            m_config.filament_map_2.values[index] = m_ori_full_print_config.get_index_for_extruder(f_maps[index], "print_extruder_id", extruder_type, nozzle_volume_type, "print_extruder_variant");
+            // Orca: when the process variant columns cannot be matched (degenerate
+            // print_extruder_id), key the override by plain extruder index like the seeding
+            // above instead of poisoning the map with -1.
+            int slot_index = m_ori_full_print_config.get_index_for_extruder(f_maps[index], "print_extruder_id", extruder_type, nozzle_volume_type, "print_extruder_variant");
+            m_config.filament_map_2.values[index] = slot_index >= 0 ? slot_index : f_maps[index] - 1;
         }
 
         m_full_print_config = m_ori_full_print_config;
@@ -4017,10 +4021,33 @@ void Print::_make_wipe_tower()
         // in BBL machine, wipe tower is only use to prime extruder. So just use a global wipe volume.
         WipeTower wipe_tower(m_config, m_plate_index, m_origin, m_wipe_tower_data.tool_ordering.first_extruder(),
                              m_wipe_tower_data.tool_ordering.empty() ? 0.f : m_wipe_tower_data.tool_ordering.back().print_z, m_wipe_tower_data.tool_ordering.all_extruders());
+        // Orca: the tower's first-layer flow follows the user's first-layer flow ratio (BBS reads
+        // its initial_layer_flow_ratio here — STUDIO-14254; first_layer_flow_ratio is Orca's analog,
+        // default 1.0 in both). Honor the set_other_flow_ratios gate that governs the option
+        // everywhere else.
+        wipe_tower.set_first_layer_flow_ratio(m_default_object_config.set_other_flow_ratios
+                                                  ? float(m_default_region_config.first_layer_flow_ratio)
+                                                  : 1.f);
         wipe_tower.set_has_tpu_filament(this->has_tpu_filament());
-        wipe_tower.set_filament_map(this->get_filament_maps());
-        // Vortek H2C: pass nozzle-level map for carousel rotation detection in tool_change_new()
-        wipe_tower.set_filament_nozzle_map(this->get_filament_nozzle_maps());
+        // Per-layer filament->nozzle grouping. sort_and_build_data() above publishes it on the Print
+        // for by-layer prints; by-object prints publish only later (psSkirtBrim), so fall back to the
+        // ToolOrdering's own copy there. set_extruder() below dereferences it, so it must be set first.
+        auto print_group_result = get_layered_nozzle_group_result();
+        const MultiNozzleUtils::LayeredNozzleGroupResult &nozzle_group_result =
+            print_group_result ? *print_group_result : m_wipe_tower_data.tool_ordering.get_layered_nozzle_group_result();
+        wipe_tower.set_nozzle_group_result(nozzle_group_result);
+        {
+            // Orca: acceleration options are object-scope (PrintConfig members in BBS), so resolve
+            // the per-variant columns here; initial_layer_travel_acceleration is FloatOrPercent
+            // over travel_acceleration and needs the full config to resolve.
+            std::vector<double> first_layer_travel_accels;
+            for (size_t i = 0; i < m_config.initial_layer_travel_acceleration.values.size(); ++i)
+                first_layer_travel_accels.emplace_back(m_full_print_config.get_abs_value_at("initial_layer_travel_acceleration", i));
+            wipe_tower.set_accelerations(m_default_object_config.default_acceleration.values,
+                                         m_default_object_config.initial_layer_acceleration.values,
+                                         m_default_object_config.travel_acceleration.values,
+                                         first_layer_travel_accels);
+        }
         // Feed the has_filament_switcher device flag (develop-only dynamic key, read defensively from
         // the full config — no shipping profile sets it) and the shared printable bed used by the PETG
         // pre-extrusion offset clamp. Both are inert unless has_filament_switcher is set.
@@ -4056,27 +4083,19 @@ void Print::_make_wipe_tower()
             multi_extruder_flush.emplace_back(wipe_volumes);
         }
 
-        // Use NozzleStatusRecorder for per-carousel-slot tracking (BBS pattern).
-        // The original Orca code tracked per-extruder (2 slots), which collapsed all
-        // carousel filaments into one slot and caused massive redundant AMS flushing.
-        auto group_result = get_layered_nozzle_group_result();
+        // Per-carousel-slot purge tracking via NozzleStatusRecorder (BBS pattern); the layered
+        // group result set on the tower above resolves each filament to its nozzle slot per layer.
         MultiNozzleUtils::NozzleStatusRecorder nozzle_recorder;
-        // Fallback (group_result == null) per-physical-nozzle tracking, matching the original
-        // pre-port behavior: remembers the last filament loaded in each physical nozzle slot.
-        std::vector<unsigned int> nozzle_cur_filament_ids(nozzle_nums, (unsigned int) -1);
 
         std::vector<int>filament_maps = get_filament_maps();
         int layer_idx = -1;
 
         unsigned int current_filament_id = m_wipe_tower_data.tool_ordering.first_extruder();
         // Initialize NozzleStatusRecorder with the first filament's carousel slot
-        if (group_result) {
-            auto nozzle = group_result->get_nozzle_for_filament(current_filament_id, layer_idx);
+        {
+            auto nozzle = nozzle_group_result.get_nozzle_for_filament(current_filament_id, layer_idx);
             if (nozzle)
                 nozzle_recorder.set_nozzle_status(nozzle->group_id, current_filament_id, nozzle->extruder_id);
-        } else {
-            size_t cur_nozzle_id = filament_maps[current_filament_id] - 1;
-            nozzle_cur_filament_ids[cur_nozzle_id] = current_filament_id;
         }
 
         for (auto& layer_tools : m_wipe_tower_data.tool_ordering.layer_tools()) { // for all layers
@@ -4095,8 +4114,8 @@ void Print::_make_wipe_tower()
                 float volume_to_purge = 0;
 
                 // Per-carousel-slot purge tracking via NozzleStatusRecorder
-                if (group_result) {
-                    auto nozzle_info = group_result->get_nozzle_for_filament(filament_id, layer_idx);
+                {
+                    auto nozzle_info = nozzle_group_result.get_nozzle_for_filament(filament_id, layer_idx);
                     if (nozzle_info) {
                         int extruder_id = nozzle_info->extruder_id;
                         int nozzle_id   = nozzle_info->group_id;
@@ -4115,22 +4134,6 @@ void Print::_make_wipe_tower()
                         }
                         nozzle_recorder.set_nozzle_status(nozzle_id, filament_id, extruder_id);
                     }
-                } else {
-                    // Fallback: original Orca per-physical-nozzle path (non-carousel printers).
-                    // Flush source is the last filament that occupied THIS nozzle, guarded so the
-                    // first use of a nozzle incurs no flush.
-                    int nozzle_id = filament_maps[filament_id] - 1;
-                    unsigned int pre_filament_id = nozzle_cur_filament_ids[nozzle_id];
-                    if (pre_filament_id != (unsigned int) -1 && pre_filament_id != filament_id) {
-                        volume_to_purge = multi_extruder_flush[nozzle_id][pre_filament_id][filament_id];
-                        float flush_multiplier = (m_config.prime_volume_mode == PrimeVolumeMode::pvmFast)
-                            ? m_config.flush_multiplier_fast.get_at(nozzle_id)
-                            : m_config.flush_multiplier.get_at(nozzle_id);
-                        volume_to_purge *= flush_multiplier;
-                        volume_to_purge = layer_tools.wiping_extrusions().mark_wiping_extrusions(
-                            *this, current_filament_id, filament_id, volume_to_purge);
-                    }
-                    nozzle_cur_filament_ids[nozzle_id] = filament_id;
                 }
 
                 //During the filament change, the extruder will extrude an extra length of grab_length for the corresponding detection, so the purge can reduce this length.
@@ -4138,29 +4141,21 @@ void Print::_make_wipe_tower()
                 float grab_purge_volume = m_config.grab_length.get_at(grab_extruder_id) * 2.4; //(diameter/2)^2*PI=2.4
                 volume_to_purge = std::max(0.f, volume_to_purge - grab_purge_volume);
 
-                // Select prime volume per-filament: nozzle change (carousel rotation) uses
-                // filament_prime_volume_nc, filament change (same nozzle slot) uses filament_prime_volume.
+                // Prime volume per-filament: the tower now picks extruder-change vs nozzle-change
+                // (carousel) internally per plan layer, so pass both candidates (BBS pattern).
                 float wipe_volume_ec = filament_id < m_config.filament_prime_volume.values.size()
                     ? m_config.filament_prime_volume.values[filament_id]
                     : (float) m_config.prime_volume;
                 float wipe_volume_nc = filament_id < m_config.filament_prime_volume_nc.values.size()
                     ? m_config.filament_prime_volume_nc.values[filament_id]
                     : (float) m_config.prime_volume;
-
-                float prime_volume = wipe_volume_ec;
-                if (group_result) {
-                    bool is_nozzle_change = group_result->are_filaments_same_extruder(current_filament_id, filament_id, layer_idx) &&
-                                           !group_result->are_filaments_same_nozzle(current_filament_id, filament_id, layer_idx);
-                    if (is_nozzle_change) {
-                        prime_volume = wipe_volume_nc;
-                    }
-                }
                 if (m_config.prime_volume_mode == PrimeVolumeMode::pvmSaving) {
-                    prime_volume = 15.f;
+                    wipe_volume_ec = 15.f;
+                    wipe_volume_nc = 15.f;
                 }
 
                 wipe_tower.plan_toolchange((float)layer_tools.print_z, (float)layer_tools.wipe_tower_layer_height, current_filament_id, filament_id,
-                    prime_volume, volume_to_purge);
+                    wipe_volume_ec, wipe_volume_nc, volume_to_purge);
                 current_filament_id = filament_id;
             }
             layer_tools.wiping_extrusions().ensure_perimeters_infills_order(*this);
@@ -4338,7 +4333,12 @@ void Print::_make_wipe_tower()
                                          wipe_tower.get_rib_width(), wipe_tower.get_rib_length(),
                                          config().wipe_tower_fillet_wall.value);
         const Vec3d origin                      = Vec3d::Zero();
-        m_fake_wipe_tower.set_fake_extrusion_data(wipe_tower.position(), wipe_tower.width(), wipe_tower.get_wipe_tower_height(),
+        // FakeWipeTower::pos is a bed-frame translation applied after rotation
+        // (getFakeExtrusionPathsFromWipeTower2 rotates about the local origin), so the
+        // tower-local rib offset must be rotated into the bed frame first.
+        m_fake_wipe_tower.rib_offset = Eigen::Rotation2Df(Geometry::deg2rad((float)config().wipe_tower_rotation_angle.value)) *
+                                       wipe_tower.get_rib_offset();
+        m_fake_wipe_tower.set_fake_extrusion_data(wipe_tower.position() + m_fake_wipe_tower.rib_offset, wipe_tower.width(), wipe_tower.get_wipe_tower_height(),
                                                   config().initial_layer_print_height, m_wipe_tower_data.depth,
                                                   m_wipe_tower_data.z_and_depth_pairs, m_wipe_tower_data.brim_width,
                                                   config().wipe_tower_rotation_angle, config().wipe_tower_cone_angle,

src/libslic3r/PrintApply.cpp

@@ -1355,7 +1355,11 @@ Print::ApplyStatus Print::apply(const Model &model, DynamicPrintConfig new_full_
         if ((extruder_volume_type_count > extruder_count) && opt_filament_volume_maps
             && opt_filament_volume_maps->values.size() == filament_maps.size())
             nozzle_volume_type = (NozzleVolumeType)(opt_filament_volume_maps->values[index]);
-        m_config.filament_map_2.values[index] = new_full_config.get_index_for_extruder(filament_maps[index], "print_extruder_id", extruder_type, nozzle_volume_type, "print_extruder_variant");
+        // Orca: when the process variant columns cannot be matched (degenerate
+        // print_extruder_id), key the override by plain extruder index like the seeding
+        // above instead of poisoning the map with -1.
+        int slot_index = new_full_config.get_index_for_extruder(filament_maps[index], "print_extruder_id", extruder_type, nozzle_volume_type, "print_extruder_variant");
+        m_config.filament_map_2.values[index] = slot_index >= 0 ? slot_index : filament_maps[index] - 1;
     }
 
     // Do not use the ApplyStatus as we will use the max function when updating apply_status.
@@ -1411,6 +1415,16 @@ Print::ApplyStatus Print::apply(const Model &model, DynamicPrintConfig new_full_
             num_extruders_changed  = true;
         }
     }
+    else if (! print_diff.empty()) {
+        // Orca: m_config can diverge from an unchanged full config (e.g. the in-slice retract
+        // override recompute writing different values than the apply-time computation). The
+        // invalidation above already fired for print_diff, so repair m_config here as well;
+        // otherwise the divergence is never corrected and every subsequent apply of the same
+        // config invalidates the result again, forever.
+        m_placeholder_parser.apply_config(filament_overrides);
+        m_config.apply_only(new_full_config, print_diff, true);
+        m_config.apply(filament_overrides);
+    }
 
     ModelObjectStatusDB model_object_status_db;
 

src/libslic3r/PrintConfig.cpp

@@ -10495,6 +10495,44 @@ int DynamicPrintConfig::get_extruder_nozzle_volume_count(int extruder_count, std
     return count;
 }
 
+// Orca: BBL system profiles ship full-width print_extruder_id/print_extruder_variant columns, but
+// custom multi-extruder printers only ever get the machine-scope columns synthesized for them (see
+// extend_extruder_variant); the process scope keeps the length-1 defaults, both in presets and in
+// 3mf project configs. Expanding with that degenerate map makes every per-extruder lookup fail, and
+// because both keys are themselves in print_options_with_variant, the expansion then latches a
+// full-width-but-wrong [1,1,...] map that also defeats the generated_extruder_id fallback in
+// get_index_for_extruder. Synthesize the process columns from the printer's extruder_variant_list
+// (same token walk as extend_extruder_variant) before expanding.
+static void ensure_process_variant_columns(DynamicPrintConfig &config, const DynamicPrintConfig &printer_config)
+{
+    auto id_opt      = dynamic_cast<ConfigOptionInts *>(config.option("print_extruder_id"));
+    auto variant_opt = dynamic_cast<ConfigOptionStrings *>(config.option("print_extruder_variant"));
+    auto list_opt    = dynamic_cast<const ConfigOptionStrings *>(printer_config.option("extruder_variant_list"));
+    if (!id_opt || !variant_opt || !list_opt)
+        return;
+    if (id_opt->values.size() != 1 || variant_opt->values.size() != 1)
+        return;
+
+    std::vector<int>         ids;
+    std::vector<std::string> variants;
+    for (int i = 0; i < int(list_opt->values.size()); ++i) {
+        std::vector<std::string> tokens;
+        boost::split(tokens, list_opt->get_at(i), boost::is_any_of(","), boost::token_compress_on);
+        for (std::string &token : tokens) {
+            boost::trim(token);
+            if (token.empty())
+                continue;
+            ids.push_back(i + 1);
+            variants.push_back(token);
+        }
+    }
+    // A single column is the legitimate single-extruder layout, not a degenerate one.
+    if (ids.size() <= 1)
+        return;
+    id_opt->values      = std::move(ids);
+    variant_opt->values = std::move(variants);
+}
+
 std::vector<int> DynamicPrintConfig::update_values_to_printer_extruders(DynamicPrintConfig& printer_config, int extruder_count, int extruder_nozzle_volume_count, std::vector<std::vector<NozzleVolumeType>>& nv_types,
     std::set<std::string>& key_set, std::string id_name, std::string variant_name, unsigned int stride, unsigned int extruder_id, NozzleVolumeType filament_nvt)
 {
@@ -10536,6 +10574,8 @@ std::vector<int> DynamicPrintConfig::update_values_to_printer_extruders(DynamicP
         variant_count = 1;
     }
     else {
+        if (id_name == "print_extruder_id")
+            ensure_process_variant_columns(*this, printer_config);
         // Orca: emit the slots first, then size variant_count from what was actually
         // emitted. extruder_nozzle_volume_count only equals the emitted total when every
         // extruder carries per-type stats; an extruder with an empty stats entry combined

src/slic3r/GUI/PartPlate.cpp

@@ -2298,6 +2298,7 @@ arrangement::ArrangePolygon PartPlate::estimate_wipe_tower_polygon(const Dynamic
 	bool enable_wrapping = (wrapping_opt != nullptr) && wrapping_opt->value;
 	wt_size = estimate_wipe_tower_size(config, w, v, extruder_count, plate_extruder_size, use_global_objects, enable_wrapping);
 	int plate_width=m_width, plate_depth=m_depth;
+	w = wt_size(0); // effective width; differs from prime_tower_width when the rib wall squares the tower
 	float depth = wt_size(1);
 	float margin = WIPE_TOWER_MARGIN + tower_brim_width, wp_brim_width = 0.f;
 	const ConfigOption* wipe_tower_brim_width_opt = config.option("prime_tower_brim_width");

tests/libslic3r/test_config_variant_expansion.cpp

@@ -43,18 +43,33 @@ TEST_CASE("apply_override fills nil entries from the 0-based default index", "[C
         REQUIRE(resolved.values == std::vector<double>({30., 42.}));
     }
 
-    SECTION("an index past the machine slots falls back to the first slot") {
+    SECTION("an index past the machine slots keeps the slot's own value") {
         std::vector<int> slot_index{5, 0};
         ConfigOptionFloats resolved(machine);
         REQUIRE(resolved.apply_override(&filament, slot_index));
         REQUIRE(resolved.values == std::vector<double>({10., 42.}));
     }
 
-    SECTION("a negative index (unresolved slot) falls back to the first slot") {
-        std::vector<int> slot_index{-1, 0};
+    SECTION("a negative index (unresolved slot) keeps the slot's own value") {
+        ConfigOptionFloatsNullable all_nil;
+        all_nil.values = {ConfigOptionFloatsNullable::nil_value(), ConfigOptionFloatsNullable::nil_value(),
+                          ConfigOptionFloatsNullable::nil_value()};
+        std::vector<int> slot_index{2, -1, 0};
         ConfigOptionFloats resolved(machine);
-        REQUIRE(resolved.apply_override(&filament, slot_index));
-        REQUIRE(resolved.values == std::vector<double>({10., 42.}));
+        REQUIRE(!resolved.apply_override(&all_nil, slot_index));
+        REQUIRE(resolved.values == std::vector<double>({30., 20., 10.}));
+    }
+
+    SECTION("all-nil overrides keyed by unresolved slots leave the machine values intact") {
+        // The failed-lookup map a degenerate print_extruder_id used to produce; the negative
+        // slots must not collapse the machine array to its first value.
+        ConfigOptionFloats per_extruder({100., 70., 70., 70., 100.});
+        ConfigOptionFloatsNullable all_nil;
+        all_nil.values.assign(5, ConfigOptionFloatsNullable::nil_value());
+        std::vector<int> slot_index{0, -1, -1, -1, 0};
+        ConfigOptionFloats resolved(per_extruder);
+        REQUIRE(!resolved.apply_override(&all_nil, slot_index));
+        REQUIRE(resolved.values == std::vector<double>({100., 70., 70., 70., 100.}));
     }
 }
 
@@ -272,6 +287,102 @@ TEST_CASE("update_values_to_printer_extruders expands one slot per (extruder x v
     }
 }
 
+TEST_CASE("update_values_to_printer_extruders synthesizes degenerate process variant columns", "[Config]")
+{
+    // Non-BBL process presets and 3mf project configs keep the length-1 defaults for
+    // print_extruder_id/print_extruder_variant; only BBL system presets ship full-width columns.
+    auto add_degenerate_print_columns = [](DynamicPrintConfig &config) {
+        config.option<ConfigOptionInts>("print_extruder_id", true)->values = {1};
+        config.option<ConfigOptionStrings>("print_extruder_variant", true)->values = {"Direct Drive Standard"};
+        config.option<ConfigOptionFloats>("outer_wall_speed", true)->values = {30.};
+    };
+
+    SECTION("a single-column pair on a multi-extruder machine expands to one column per extruder") {
+        DynamicPrintConfig config;
+        config.option<ConfigOptionEnumsGeneric>("extruder_type", true)->values = {etDirectDrive, etDirectDrive};
+        config.option<ConfigOptionEnumsGeneric>("nozzle_volume_type", true)->values = {nvtStandard, nvtStandard};
+        config.option<ConfigOptionStrings>("extruder_variant_list", true)->values = {"Direct Drive Standard", "Direct Drive Standard"};
+        add_degenerate_print_columns(config);
+
+        std::vector<std::vector<NozzleVolumeType>> nozzle_volume_types;
+        int extruder_count = 2;
+        int count = config.get_extruder_nozzle_volume_count(extruder_count, nozzle_volume_types);
+
+        std::vector<int> variant_index = config.update_values_to_printer_extruders(config, extruder_count, count, nozzle_volume_types,
+            print_options_with_variant, "print_extruder_id", "print_extruder_variant");
+
+        REQUIRE(variant_index == std::vector<int>({0, 1}));
+        REQUIRE(config.option<ConfigOptionInts>("print_extruder_id")->values == std::vector<int>({1, 2}));
+        REQUIRE(config.option<ConfigOptionStrings>("print_extruder_variant")->values ==
+                std::vector<std::string>({"Direct Drive Standard", "Direct Drive Standard"}));
+        // width-1 data arrays replicate their only column into every slot
+        REQUIRE(config.option<ConfigOptionFloats>("outer_wall_speed")->values == std::vector<double>({30., 30.}));
+    }
+
+    SECTION("a multi-variant list synthesizes one column per (extruder x variant)") {
+        DynamicPrintConfig config = make_hybrid_printer_config();
+        add_degenerate_print_columns(config);
+
+        std::vector<std::vector<NozzleVolumeType>> nozzle_volume_types;
+        int extruder_count = 2;
+        int count = config.get_extruder_nozzle_volume_count(extruder_count, nozzle_volume_types);
+        REQUIRE(count == 3);
+
+        std::vector<int> variant_index = config.update_values_to_printer_extruders(config, extruder_count, count, nozzle_volume_types,
+            print_options_with_variant, "print_extruder_id", "print_extruder_variant");
+
+        // same slot resolution as the explicit BBL-style 4-column layout
+        REQUIRE(variant_index == std::vector<int>({0, 2, 3}));
+        REQUIRE(config.option<ConfigOptionInts>("print_extruder_id")->values == std::vector<int>({1, 2, 2}));
+        REQUIRE(config.option<ConfigOptionStrings>("print_extruder_variant")->values ==
+                std::vector<std::string>({"Direct Drive Standard", "Direct Drive Standard", "Direct Drive High Flow"}));
+        REQUIRE(config.option<ConfigOptionFloats>("outer_wall_speed")->values == std::vector<double>({30., 30., 30.}));
+    }
+
+    SECTION("a single-extruder single-column layout is not treated as degenerate") {
+        DynamicPrintConfig config;
+        config.option<ConfigOptionEnumsGeneric>("extruder_type", true)->values = {etDirectDrive};
+        config.option<ConfigOptionEnumsGeneric>("nozzle_volume_type", true)->values = {nvtStandard};
+        config.option<ConfigOptionStrings>("extruder_variant_list", true)->values = {"Direct Drive Standard"};
+        add_degenerate_print_columns(config);
+
+        std::vector<std::vector<NozzleVolumeType>> nozzle_volume_types;
+        int extruder_count = 1;
+        int count = config.get_extruder_nozzle_volume_count(extruder_count, nozzle_volume_types);
+
+        config.update_values_to_printer_extruders(config, extruder_count, count, nozzle_volume_types,
+            print_options_with_variant, "print_extruder_id", "print_extruder_variant");
+
+        REQUIRE(config.option<ConfigOptionInts>("print_extruder_id")->values == std::vector<int>({1}));
+        REQUIRE(config.option<ConfigOptionFloats>("outer_wall_speed")->values == std::vector<double>({30.}));
+    }
+
+    SECTION("a second expansion leaves the synthesized layout unchanged") {
+        DynamicPrintConfig config;
+        config.option<ConfigOptionEnumsGeneric>("extruder_type", true)->values = {etDirectDrive, etDirectDrive};
+        config.option<ConfigOptionEnumsGeneric>("nozzle_volume_type", true)->values = {nvtStandard, nvtStandard};
+        config.option<ConfigOptionStrings>("extruder_variant_list", true)->values = {"Direct Drive Standard", "Direct Drive Standard"};
+        add_degenerate_print_columns(config);
+
+        std::vector<std::vector<NozzleVolumeType>> nozzle_volume_types;
+        int extruder_count = 2;
+        int count = config.get_extruder_nozzle_volume_count(extruder_count, nozzle_volume_types);
+
+        config.update_values_to_printer_extruders(config, extruder_count, count, nozzle_volume_types,
+            print_options_with_variant, "print_extruder_id", "print_extruder_variant");
+        DynamicPrintConfig once = config;
+        config.update_values_to_printer_extruders(config, extruder_count, count, nozzle_volume_types,
+            print_options_with_variant, "print_extruder_id", "print_extruder_variant");
+
+        REQUIRE(config.option<ConfigOptionInts>("print_extruder_id")->values ==
+                once.option<ConfigOptionInts>("print_extruder_id")->values);
+        REQUIRE(config.option<ConfigOptionStrings>("print_extruder_variant")->values ==
+                once.option<ConfigOptionStrings>("print_extruder_variant")->values);
+        REQUIRE(config.option<ConfigOptionFloats>("outer_wall_speed")->values ==
+                once.option<ConfigOptionFloats>("outer_wall_speed")->values);
+    }
+}
+
 TEST_CASE("update_values_to_printer_extruders_for_multiple_filaments resolves per-filament slots", "[Config]")
 {
     auto make_filament_arrays = [](DynamicPrintConfig &config) {

tests/libslic3r/test_toolordering_nozzle_group.cpp

@@ -500,6 +500,52 @@ TEST_CASE("Re-applying an unchanged config after slicing keeps the result valid"
     REQUIRE(print.is_step_done(psSlicingFinished));
 }
 
+TEST_CASE("A degenerate process variant map on a custom multi-extruder printer slices to a stable result", "[Print][Regression]")
+{
+    // Non-BBL multi-extruder printers get machine-scope variant columns synthesized on preset
+    // load (extend_extruder_variant), but nothing ships process-scope print_extruder_id /
+    // print_extruder_variant: presets and 3mf project configs carry the length-1 defaults. The
+    // apply-time expansion must synthesize the process columns from extruder_variant_list;
+    // otherwise the failed per-extruder lookups collapse the per-extruder retract overrides
+    // during slicing and the post-slice re-apply invalidates every fresh result, forever.
+    DynamicPrintConfig config = DynamicPrintConfig::full_print_config();
+    config.option<ConfigOptionFloats>("nozzle_diameter", true)->values = {0.4, 0.4, 0.4, 0.4, 0.4};
+    config.set_num_extruders(5);
+    // per-extruder machine values that a first-slot collapse would destroy
+    config.option<ConfigOptionPercents>("retract_before_wipe", true)->values = {100., 70., 70., 70., 100.};
+    config.option<ConfigOptionEnumsGeneric>("z_hop_types", true)->values = {zhtSlope, zhtNormal, zhtNormal, zhtNormal, zhtSlope};
+    // filament presets carry the nullable override twins (all-nil = "no override"); they are what
+    // routes the machine values through apply_override in the in-slice override recompute
+    config.option<ConfigOptionPercentsNullable>("filament_retract_before_wipe", true)->values =
+        std::vector<double>(5, ConfigOptionPercentsNullable::nil_value());
+    config.option<ConfigOptionEnumsGenericNullable>("filament_z_hop_types", true)->values =
+        std::vector<int>(5, ConfigOptionEnumsGenericNullable::nil_value());
+    config.option<ConfigOptionFloats>("filament_diameter", true)->values = std::vector<double>(5, 1.75);
+    config.option<ConfigOptionStrings>("filament_colour", true)->values = {"#FF0000", "#00FF00", "#0000FF", "#FFFF00", "#00FFFF"};
+    config.option<ConfigOptionInts>("filament_map", true)->values = {1, 2, 3, 4, 1};
+
+    Model model;
+    model.add_object("cube", "", make_cube(20, 20, 20))->add_instance()->set_offset(Vec3d(100., 100., 0.));
+
+    Print print;
+    print.apply(model, config);
+    print.process();
+    REQUIRE(print.is_step_done(psSlicingFinished));
+
+    // BackgroundSlicingProcess reads the engine-computed maps back into the plate config after
+    // slicing; the next apply overlays that written-back state.
+    config.option<ConfigOptionInts>("filament_map", true)->values = print.get_filament_maps();
+    config.option<ConfigOptionInts>("filament_volume_map", true)->values = print.get_filament_volume_maps();
+    config.option<ConfigOptionInts>("filament_nozzle_map", true)->values = print.get_filament_nozzle_maps();
+
+    auto status = print.apply(model, config);
+    REQUIRE(status == PrintBase::APPLY_STATUS_UNCHANGED);
+    REQUIRE(print.is_step_done(psSlicingFinished));
+    // the per-extruder machine values must survive the in-slice override recompute
+    REQUIRE(print.config().retract_before_wipe.values == std::vector<double>({100., 70., 70., 70., 100.}));
+    REQUIRE(print.config().z_hop_types.values == std::vector<int>({zhtSlope, zhtNormal, zhtNormal, zhtNormal, zhtSlope}));
+}
+
 TEST_CASE("normalize_nozzle_map_per_layer makes per-filament assignments gap-free", "[MultiNozzle][H2C][Dynamic]")
 {
     SECTION("gaps inherit the last used nozzle, entries on used layers stay untouched") {