Refactor skirt/brim + bugfixes related to them (#14333)

Refactor skirt and brim ownership and emission flow

Refactor skirt and brim generation around a common object/group
ownership model.

Skirts and brims are now emitted as a coordinated preamble
(skirt -> brim -> object) instead of being generated and emitted
through multiple independent code paths.

Changes:
- Fix repeated skirt emission caused by the previous skirt state
  tracking logic.
- Restore local skirt/brim ordering for per-object skirts in
  By Layer mode.
- Emit brims together with their owning object or object group.
- Handle combined brims independently from skirt grouping.
- Handle draft shields through the same ownership model as skirts.
- Fix draft shield generation when skirt height is zero.
- Generate draft shields after brim geometry is known, preventing
  draft shields from overlapping brims.
- Reject unsafe grouped per-object skirt configurations in
  By Object mode.
- Remove legacy skirt emission paths and state-management
  workarounds.

Support brim generation remains unchanged.

Co-authored-by: SoftFever <softfeverever@gmail.com>

src/libslic3r/Brim.cpp

@@ -833,8 +833,7 @@ Polygons tryExPolygonOffset(const ExPolygons& islandAreaEx, const Print& print)
     }
     return loops;
 }
-//BBS: a function creates the ExtrusionEntityCollection from the brim area defined by ExPolygons
-ExtrusionEntityCollection makeBrimInfill(const ExPolygons& singleBrimArea, const Print& print, const Polygons& islands_area) {
+static ExtrusionEntityCollection makeBrimInfillImpl(const ExPolygons& singleBrimArea, const Print& print, const Polygons& islands_area, bool apply_plate_offset) {
     Polygons        loops = tryExPolygonOffset(singleBrimArea, print);
     Flow  flow = print.brim_flow();
     loops = union_pt_chained_outside_in(loops);
@@ -864,16 +863,29 @@ ExtrusionEntityCollection makeBrimInfill(const ExPolygons& singleBrimArea, const
     optimize_polylines_by_reversing(&all_loops);
     all_loops = connect_brim_lines(std::move(all_loops), offset(singleBrimArea, float(SCALED_EPSILON)), float(flow.scaled_spacing()) * 2.f);
 
-    //BBS: finally apply the plate offset which may very large
-    auto plate_offset = print.get_plate_origin();
-    Point scaled_plate_offset = Point(scaled(plate_offset.x()), scaled(plate_offset.y()));
-    for (Polyline& one_loop : all_loops)
-        one_loop.translate(scaled_plate_offset);
+    if (apply_plate_offset) {
+        //BBS: finally apply the plate offset which may very large
+        auto plate_offset = print.get_plate_origin();
+        Point scaled_plate_offset = Point(scaled(plate_offset.x()), scaled(plate_offset.y()));
+        for (Polyline& one_loop : all_loops)
+            one_loop.translate(scaled_plate_offset);
+    }
 
     extrusion_entities_append_loops_and_paths(brim.entities, std::move(all_loops), erBrim, float(flow.mm3_per_mm()), float(flow.width()), float(print.skirt_first_layer_height()));
     return brim;
 }
 
+//BBS: a function creates the ExtrusionEntityCollection from the brim area defined by ExPolygons
+ExtrusionEntityCollection makeBrimInfill(const ExPolygons& singleBrimArea, const Print& print, const Polygons& islands_area)
+{
+    return makeBrimInfillImpl(singleBrimArea, print, islands_area, true);
+}
+
+ExtrusionEntityCollection makeBrimInfillFromPlateCoordinates(const ExPolygons& singleBrimArea, const Print& print, const Polygons& islands_area)
+{
+    return makeBrimInfillImpl(singleBrimArea, print, islands_area, false);
+}
+
 //BBS: an overload of the orignal brim generator that generates the brim by obj and by extruders
 void make_brim(const Print& print, PrintTryCancel try_cancel, Polygons& islands_area,
     std::map<ObjectID, ExtrusionEntityCollection>& brimMap,
@@ -943,11 +955,13 @@ void make_brim(const Print& print, PrintTryCancel try_cancel, Polygons& islands_
     if (supportBrimAreasOut != nullptr)
         *supportBrimAreasOut = translate_area_map(supportBrimAreaMap);
 
-    const bool combine_brims     = print.config().combine_brims.value;
-    const bool is_by_object      = (print.config().print_sequence == PrintSequence::ByObject);
-    const bool can_combine_brims = combine_brims && !is_by_object;
+    const bool has_per_object_skirt_or_shield = print.config().skirt_type == stPerObject &&
+                                                (print.has_skirt() || print.has_infinite_skirt());
+    const bool combine_brims = print.config().combine_brims.value &&
+                               !has_per_object_skirt_or_shield &&
+                               print.config().print_sequence != PrintSequence::ByObject;
 
-    if (!can_combine_brims) {
+    if (!combine_brims) {
         // Orca: Generate brims separately when brims cannot be combined.
         for (auto iter = brimAreaMap.begin(); iter != brimAreaMap.end(); ++iter) {
             if (!iter->second.empty()) {
@@ -960,7 +974,7 @@ void make_brim(const Print& print, PrintTryCancel try_cancel, Polygons& islands_
             };
         }
     } else {
-        // Orca: Unified brim mode (non-sequential printing)
+        // Orca: Unified brim mode.
         ExPolygons            all_brims_merged;
         std::vector<ObjectID> brim_object_ids;
 

src/libslic3r/Brim.hpp

@@ -24,6 +24,9 @@ void make_brim(const Print& print, PrintTryCancel try_cancel,
     std::map<ObjectID, ExPolygons>* objectBrimAreasOut = nullptr,
     std::map<ObjectID, ExPolygons>* supportBrimAreasOut = nullptr);
 
+ExtrusionEntityCollection makeBrimInfill(const ExPolygons& singleBrimArea, const Print& print, const Polygons& islands_area);
+ExtrusionEntityCollection makeBrimInfillFromPlateCoordinates(const ExPolygons& singleBrimArea, const Print& print, const Polygons& islands_area);
+
 // BBS: automatically make brim
 ExtrusionEntityCollection make_brim_auto(const Print &print, PrintTryCancel try_cancel, Polygons &islands_area);
 

src/libslic3r/GCode.cpp

@@ -2032,6 +2032,7 @@ void GCode::do_export(Print* print, const char* path, GCodeProcessorResult* resu
 
     // BBS
     m_curr_print = print;
+    m_skirt_group_done.clear();
 
     GCodeWriter::full_gcode_comment = print->config().gcode_comments;
     CNumericLocalesSetter locales_setter;
@@ -3223,6 +3224,11 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
         // Ugly hack: Do not set the initial extruder if the extruder is primed using the MMU priming towers at the edge of the print bed.
         file.write(this->set_extruder(initial_extruder_id, 0.));
     }
+
+    this->m_objsWithBrim.clear();
+    this->m_objSupportsWithBrim.clear();
+    m_brim_done = false;
+
     // BBS: set that indicates objs with brim
     for (auto iter = print.m_brimMap.begin(); iter != print.m_brimMap.end(); ++iter) {
         if (!iter->second.empty())
@@ -4282,7 +4288,8 @@ namespace Skirt {
         std::map<unsigned int, std::pair<size_t, size_t>> skirt_loops_per_extruder_out;
         //For sequential print, the following test may fail when extruding the 2nd and other objects.
         // assert(skirt_done.empty());
-        if (skirt_done.empty() && print.has_skirt() && ! skirt.entities.empty() && layer_tools.has_skirt) {
+        const bool has_skirt_or_draft_shield = print.has_skirt() || print.has_infinite_skirt();
+        if (skirt_done.empty() && has_skirt_or_draft_shield && ! skirt.entities.empty() && layer_tools.has_skirt) {
             skirt_loops_per_extruder_all_printing(print, skirt, layer_tools, skirt_loops_per_extruder_out);
             skirt_done.emplace_back(layer_tools.print_z);
         }
@@ -4299,15 +4306,16 @@ namespace Skirt {
         // Extrude skirt at the print_z of the raft layers and normal object layers
         // not at the print_z of the interlaced support material layers.
         std::map<unsigned int, std::pair<size_t, size_t>> skirt_loops_per_extruder_out;
-        if (print.has_skirt() && ! skirt.entities.empty() && layer_tools.has_skirt &&
+        const bool has_skirt_or_draft_shield = print.has_skirt() || print.has_infinite_skirt();
+        if (has_skirt_or_draft_shield && ! skirt.entities.empty() && layer_tools.has_skirt &&
             // Not enough skirt layers printed yet.
             //FIXME infinite or high skirt does not make sense for sequential print!
             (skirt_done.size() < (size_t)print.config().skirt_height.value || print.has_infinite_skirt())) {
-            bool valid = ! skirt_done.empty() && skirt_done.back() < layer_tools.print_z - EPSILON;
-            assert(valid);
-            // This print_z has not been extruded yet (sequential print)
-            // FIXME: The skirt_done should not be empty at this point. The check is a workaround
-            if (valid) {
+            assert(!skirt_done.empty());
+            if (skirt_done.empty())
+                return skirt_loops_per_extruder_out;
+            // This print_z has not been extruded yet.
+            if (skirt_done.back() < layer_tools.print_z - EPSILON) {
 #if 0
                 // Prime just the first printing extruder. This is original Slic3r's implementation.
                 skirt_loops_per_extruder_out[layer_tools.extruders.front()] = std::pair<size_t, size_t>(0, print.config().skirt_loops.value);
@@ -4315,7 +4323,6 @@ namespace Skirt {
                 // Prime all extruders planned for this layer, see
                 skirt_loops_per_extruder_all_printing(print, skirt, layer_tools, skirt_loops_per_extruder_out);
 #endif
-                assert(!skirt_done.empty());
                 skirt_done.emplace_back(layer_tools.print_z);
             }
         }
@@ -4382,7 +4389,8 @@ std::string GCode::generate_skirt(const Print &print,
         const float skirt_start_angle,
         const LayerTools &layer_tools,
         const Layer& layer,
-        unsigned int extruder_id)
+        unsigned int extruder_id,
+        std::vector<coordf_t> &skirt_done)
 {
     
     bool first_layer = (layer.id() == 0 && abs(layer.bottom_z()) < EPSILON);
@@ -4392,8 +4400,8 @@ std::string GCode::generate_skirt(const Print &print,
     // Map from extruder ID to <begin, end> index of skirt loops to be extruded with that extruder.
     std::map<unsigned int, std::pair<size_t, size_t>> skirt_loops_per_extruder;
     skirt_loops_per_extruder = first_layer ?
-        Skirt::make_skirt_loops_per_extruder_1st_layer(print, skirt, layer_tools, m_skirt_done) :
-        Skirt::make_skirt_loops_per_extruder_other_layers(print, skirt, layer_tools, m_skirt_done);
+        Skirt::make_skirt_loops_per_extruder_1st_layer(print, skirt, layer_tools, skirt_done) :
+        Skirt::make_skirt_loops_per_extruder_other_layers(print, skirt, layer_tools, skirt_done);
 
     if (auto loops_it = skirt_loops_per_extruder.find(extruder_id); loops_it != skirt_loops_per_extruder.end()) {
         const std::pair<size_t, size_t> loops = loops_it->second;
@@ -4401,7 +4409,7 @@ std::string GCode::generate_skirt(const Print &print,
         set_origin(unscaled(offset));
 
         m_avoid_crossing_perimeters.use_external_mp();
-        Flow layer_skirt_flow = print.skirt_flow().with_height(float(m_skirt_done.back() - (m_skirt_done.size() == 1 ? 0. : m_skirt_done[m_skirt_done.size() - 2])));
+        Flow layer_skirt_flow = print.skirt_flow().with_height(float(skirt_done.back() - (skirt_done.size() == 1 ? 0. : skirt_done[skirt_done.size() - 2])));
         double mm3_per_mm = layer_skirt_flow.mm3_per_mm();
         // Decide where to start looping:
         // - If it’s the first layer or if we do NOT want a single-wall skirt/draft shield,
@@ -4443,6 +4451,84 @@ std::string GCode::generate_skirt(const Print &print,
     return gcode;
 }
 
+static size_t find_skirt_brim_group_idx(const Print& print, ObjectID object_id)
+{
+    const std::vector<Print::SkirtBrimGroup>& groups = print.skirt_brim_groups();
+    for (size_t idx = 0; idx < groups.size(); ++idx)
+        if (std::find(groups[idx].object_ids.begin(), groups[idx].object_ids.end(), object_id) != groups[idx].object_ids.end())
+            return idx;
+    return size_t(-1);
+}
+
+std::string GCode::generate_object_skirt_group(const Print &print,
+        const PrintObject &object,
+        const LayerTools &layer_tools,
+        const Layer& layer,
+        unsigned int extruder_id)
+{
+    if (print.config().skirt_type != stPerObject || print.skirt_brim_groups().empty())
+        return {};
+
+    const size_t group_idx = find_skirt_brim_group_idx(print, object.id());
+    if (group_idx == size_t(-1) || print.skirt_brim_groups()[group_idx].skirt.empty())
+        return {};
+
+    LayerTools object_skirt_tools = layer_tools;
+    object_skirt_tools.extruders  = { extruder_id };
+    object_skirt_tools.has_skirt  = true;
+
+    return generate_skirt(print, print.skirt_brim_groups()[group_idx].skirt, Point(0, 0), object.config().skirt_start_angle,
+                          object_skirt_tools, layer, extruder_id, m_skirt_group_done[group_idx]);
+}
+
+std::string GCode::generate_object_brim(const Print &print, const PrintObject &object, bool first_layer)
+{
+    if (!first_layer)
+        return {};
+
+    auto emit_brim = [this](const ExtrusionEntityCollection& brim, const std::vector<ObjectID>& object_ids) {
+        std::string gcode;
+        const bool already_emitted = std::none_of(object_ids.begin(), object_ids.end(), [this](ObjectID object_id) {
+            return m_objsWithBrim.find(object_id) != m_objsWithBrim.end();
+        });
+        if (already_emitted || brim.empty())
+            return gcode;
+
+        this->set_origin(0., 0.);
+        m_avoid_crossing_perimeters.use_external_mp();
+        for (const ExtrusionEntity* ee : brim.entities)
+            if (ee != nullptr)
+                gcode += this->extrude_entity(*ee, "brim", m_config.support_speed.value);
+        m_avoid_crossing_perimeters.use_external_mp(false);
+        m_avoid_crossing_perimeters.disable_once();
+        for (ObjectID object_id : object_ids)
+            m_objsWithBrim.erase(object_id);
+        return gcode;
+    };
+
+    const bool has_per_object_skirt_or_shield = print.config().skirt_type == stPerObject &&
+                                                (print.has_skirt() || print.has_infinite_skirt());
+    if (print.config().combine_brims && !has_per_object_skirt_or_shield &&
+        print.config().print_sequence != PrintSequence::ByObject && print.m_brimMap.size() == 1) {
+        const auto brim_it = print.m_brimMap.begin();
+        return emit_brim(brim_it->second, { brim_it->first });
+    }
+
+    const size_t group_idx = find_skirt_brim_group_idx(print, object.id());
+    if (group_idx != size_t(-1)) {
+        std::string gcode;
+        for (const Print::SkirtBrimGroup::Brim& brim : print.skirt_brim_groups()[group_idx].brims)
+            if (std::find(brim.object_ids.begin(), brim.object_ids.end(), object.id()) != brim.object_ids.end())
+                gcode += emit_brim(brim.brim, brim.object_ids);
+        return gcode;
+    }
+
+    const auto brim_it = print.m_brimMap.find(object.id());
+    if (brim_it == print.m_brimMap.end())
+        return {};
+    return emit_brim(brim_it->second, { object.id() });
+}
+
 // In sequential mode, process_layer is called once per each object and its copy,
 // therefore layers will contain a single entry and single_object_instance_idx will point to the copy of the object.
 // In non-sequential mode, process_layer is called per each print_z height with all object and support layers accumulated.
@@ -4554,8 +4640,6 @@ LayerResult GCode::process_layer(
     }
 
     PrinterStructure printer_structure           = m_config.printer_structure.value;
-    PrintSequence print_sequence = m_config.print_sequence;
-    bool sequence_by_layer = print_sequence == PrintSequence::ByLayer;
     bool is_i3_printer = printer_structure == PrinterStructure::psI3;
     bool is_multi_extruder = m_config.nozzle_diameter.size() > 1;
 
@@ -5151,27 +5235,17 @@ LayerResult GCode::process_layer(
     bool has_insert_wrapping_detection_gcode = false;
 
     // Extrude the skirt, brim, support, perimeters, infill ordered by the extruders.
+    m_skirt_group_done.resize(print.skirt_brim_groups().size());
     for (unsigned int extruder_id : layer_tools.extruders)
     {
-        if ((print.config().skirt_type == stCombined ||
-             (print.config().skirt_type == stPerObject && print.config().print_sequence == PrintSequence::ByLayer)) &&
-            !print.skirt_groups().empty()) {
-            bool skirt_generated_for_current_print_z = false;
-            for (const ExtrusionEntityCollection& skirt_group : print.skirt_groups()) {
-                if (skirt_group.empty())
+        if (print.config().skirt_type == stCombined && !print.skirt_brim_groups().empty()) {
+            for (size_t group_idx = 0; group_idx < print.skirt_brim_groups().size(); ++group_idx) {
+                const Print::SkirtBrimGroup& group = print.skirt_brim_groups()[group_idx];
+                if (group.skirt.empty())
                     continue;
 
-                // Orca: each grouped skirt is emitted as its own collection so higher skirt layers
-                // follow the same per-group behavior as the first layer.
-                if (first_layer)
-                    m_skirt_done.clear();
-                else if (skirt_generated_for_current_print_z && !m_skirt_done.empty())
-                    m_skirt_done.pop_back();
-
-                std::string skirt_gcode = generate_skirt(print, skirt_group, Point(0, 0), layer.object()->config().skirt_start_angle,
-                                                          layer_tools, layer, extruder_id);
-                if (!skirt_gcode.empty())
-                    skirt_generated_for_current_print_z = true;
+                std::string skirt_gcode = generate_skirt(print, group.skirt, Point(0, 0), layer.object()->config().skirt_start_angle,
+                                                          layer_tools, layer, extruder_id, m_skirt_group_done[group_idx]);
                 gcode += std::move(skirt_gcode);
             }
         }
@@ -5245,108 +5319,20 @@ LayerResult GCode::process_layer(
 
         std::vector<InstanceToPrint> &instances_to_print = filament_to_print_instances[extruder_id];
 
-        // BBS
-        if (print.config().skirt_type == stPerObject &&
-            print.config().print_sequence == PrintSequence::ByObject &&
-            !layer.object()->object_skirt().empty() &&
-            ((layer.id() < print.config().skirt_height || print.config().draft_shield == DraftShield::dsEnabled))
-           )
-        {
-            for (InstanceToPrint& instance_to_print : instances_to_print) {
-                
-                if (instance_to_print.print_object.object_skirt().empty())
-                    continue;
-                
-                if (this->m_objSupportsWithBrim.find(instance_to_print.print_object.id()) != this->m_objSupportsWithBrim.end() &&
-                    print.m_supportBrimMap.at(instance_to_print.print_object.id()).entities.size() > 0)
-                    continue;
-
-                if (this->m_objsWithBrim.find(instance_to_print.print_object.id()) != this->m_objsWithBrim.end() &&
-                    print.m_brimMap.at(instance_to_print.print_object.id()).entities.size() > 0)
-                    continue;
-                if (first_layer)
-                    m_skirt_done.clear();
-
-                if (layer.id() == 1 && m_skirt_done.size() > 1)
-                    m_skirt_done.erase(m_skirt_done.begin()+1,m_skirt_done.end());
-
-                const Point& offset = instance_to_print.print_object.instances()[instance_to_print.instance_id].shift;
-                gcode += generate_skirt(print, instance_to_print.print_object.object_skirt(), offset, instance_to_print.print_object.config().skirt_start_angle, layer_tools, layer, extruder_id);
-            }
-        }
-
-        // Orca: Print unified global brim after the skirt and before any object.
-        // Only do this if `combine_brims` is enabled and we are printing by layer.
-        if (first_layer && sequence_by_layer && m_config.combine_brims && !print.m_brimMap.empty()) {
-            const ObjectID unified_object_id = [&]() -> ObjectID {
-                ObjectID id;
-                for (const auto& [obj_id, brim] : print.m_brimMap) {
-                    const bool has_printable_entities = std::any_of(brim.entities.begin(), brim.entities.end(),
-                                                                    [](const ExtrusionEntity* ee) { return ee != nullptr; });
-                    if (!has_printable_entities)
-                        continue;
-
-                    if (id.valid())
-                        return ObjectID();
-
-                    id = obj_id;
-                }
-                return id;
-            }();
-
-            if (unified_object_id.valid() && this->m_objsWithBrim.find(unified_object_id) != this->m_objsWithBrim.end()) {
-                const ExtrusionEntityCollection& unified_brim = print.m_brimMap.at(unified_object_id);
-                this->set_origin(0., 0.);
-                for (const ExtrusionEntity* ee : unified_brim.entities)
-                    if (ee != nullptr)
-                        gcode += this->extrude_entity(*ee, "brim", m_config.support_speed.value);
-
-                // Mark brim as printed for this object to avoid per-object brim emission later.
-                this->m_objsWithBrim.erase(unified_object_id);
-            }
-        }
-
-        // We are almost ready to print. However, we must go through all the objects twice to print the the overridden extrusions first (infill/perimeter wiping feature):
+        // We are almost ready to print. However, we must go through all the objects twice to print the overridden extrusions first (infill/perimeter wiping feature):
         std::vector<ObjectByExtruder::Island::Region> by_region_per_copy_cache;
         for (int print_wipe_extrusions = is_anything_overridden; print_wipe_extrusions>=0; --print_wipe_extrusions) {
             if (is_anything_overridden && print_wipe_extrusions == 0)
                 gcode+="; PURGING FINISHED\n";
 
-            bool skirt_generated_for_current_print_z = false;
-
             for (InstanceToPrint &instance_to_print : instances_to_print) {
-                if (print.config().skirt_type == stPerObject && 
-                    !instance_to_print.print_object.object_skirt().empty() &&
-                    print.config().print_sequence == PrintSequence::ByLayer)
-                {
-                    const LayerToPrint& layer_to_print = layers[instance_to_print.layer_id];
-                    const Layer* skirt_layer = layer_to_print.object_layer;
-                    if (skirt_layer == nullptr && layer_to_print.support_layer != nullptr &&
-                        layer_to_print.support_layer->id() < layer_to_print.support_layer->object()->slicing_parameters().raft_layers()) {
-                        skirt_layer = layer_to_print.support_layer;
-                    }
-
-                    if (skirt_layer != nullptr &&
-                        (skirt_layer->id() < print.config().skirt_height || print.config().draft_shield == DraftShield::dsEnabled)) {
-                        const bool skirt_first_layer = (skirt_layer->id() == 0 && std::abs(skirt_layer->bottom_z()) < EPSILON);
-                        if (skirt_first_layer)
-                            m_skirt_done.clear();
-
-                        if (skirt_generated_for_current_print_z && !m_skirt_done.empty())
-                            m_skirt_done.pop_back();
-
-                        const Point& offset      = instance_to_print.print_object.instances()[instance_to_print.instance_id].shift;
-                        std::string  skirt_gcode = generate_skirt(print, instance_to_print.print_object.object_skirt(), offset,
-                                                                  instance_to_print.print_object.config().skirt_start_angle, layer_tools,
-                                                                  *skirt_layer, extruder_id);
-                        if (!skirt_gcode.empty())
-                            skirt_generated_for_current_print_z = true;
-                        gcode += std::move(skirt_gcode);
-                    }
-                }
-
                 const auto& inst = instance_to_print.print_object.instances()[instance_to_print.instance_id];
                 const LayerToPrint &layer_to_print = layers[instance_to_print.layer_id];
+                if (print_wipe_extrusions == (is_anything_overridden ? 1 : 0)) {
+                    gcode += generate_object_skirt_group(print, instance_to_print.print_object, layer_tools, layer, extruder_id);
+                    gcode += generate_object_brim(print, instance_to_print.print_object, first_layer);
+                }
+
                 // To control print speed of the 1st object layer printed over raft interface.
                 bool object_layer_over_raft = layer_to_print.object_layer && layer_to_print.object_layer->id() > 0 &&
                     instance_to_print.print_object.slicing_parameters().raft_layers() == layer_to_print.object_layer->id();
@@ -5445,20 +5431,6 @@ LayerResult GCode::process_layer(
                 // Sequential tool path ordering of multiple parts within the same object, aka. perimeter tracking (#5511)
                 for (ObjectByExtruder::Island &island : instance_to_print.object_by_extruder.islands) {
                     const auto& by_region_specific = is_anything_overridden ? island.by_region_per_copy(by_region_per_copy_cache, static_cast<unsigned int>(instance_to_print.instance_id), extruder_id, print_wipe_extrusions != 0) : island.by_region;
-                    //BBS: add brim by obj by extruder
-                    if (first_layer) {
-                        if (this->m_objsWithBrim.find(instance_to_print.print_object.id()) != this->m_objsWithBrim.end() && !print_wipe_extrusions) {
-                            this->set_origin(0., 0.);
-                            m_avoid_crossing_perimeters.use_external_mp();
-                            for (const ExtrusionEntity* ee : print.m_brimMap.at(instance_to_print.print_object.id()).entities) {
-                                gcode += this->extrude_entity(*ee, "brim", m_config.support_speed.value);
-                            }
-                            m_avoid_crossing_perimeters.use_external_mp(false);
-                            // Allow a straight travel move to the first object point.
-                            m_avoid_crossing_perimeters.disable_once();
-                            this->m_objsWithBrim.erase(instance_to_print.print_object.id());
-                        }
-                    }
                     // When starting a new object, use the external motion planner for the first travel move.
                     const Point& offset = instance_to_print.print_object.instances()[instance_to_print.instance_id].shift;
                     std::pair<const PrintObject*, Point> this_object_copy(&instance_to_print.print_object, offset);

src/libslic3r/GCode.hpp

@@ -343,7 +343,16 @@ private:
         const float skirt_start_angle,
         const LayerTools &layer_tools,
         const Layer& layer,
+        unsigned int extruder_id,
+        std::vector<coordf_t> &skirt_done);
+    std::string generate_object_skirt_group(const Print &print,
+        const PrintObject &object,
+        const LayerTools &layer_tools,
+        const Layer& layer,
         unsigned int extruder_id);
+    std::string generate_object_brim(const Print &print,
+        const PrintObject &object,
+        bool first_layer);
 
     LayerResult process_layer(
         const Print                     &print,
@@ -609,8 +618,8 @@ private:
 
     std::unique_ptr<SmallAreaInfillFlowCompensator> m_small_area_infill_flow_compensator;
     
-    // Heights (print_z) at which the skirt has already been extruded.
-    std::vector<coordf_t>               m_skirt_done;
+    // Heights (print_z) at which each grouped skirt has already been extruded.
+    std::vector<std::vector<coordf_t>>   m_skirt_group_done;
     // Has the brim been extruded already? Brim is being extruded only for the first object of a multi-object print.
     bool                                m_brim_done;
     // Flag indicating whether the nozzle temperature changes from 1st to 2nd layer were performed.

src/libslic3r/Print.cpp

@@ -2443,21 +2443,14 @@ void Print::process(long long *time_cost_with_cache, bool use_cache)
             start_time = (long long)Slic3r::Utils::get_current_time_utc();
 
         m_skirt.clear();
-        m_skirt_groups.clear();
+        m_skirt_brim_groups.clear();
+        m_has_shared_per_object_skirt = false;
         m_skirt_convex_hull.clear();
         m_objectBrimAreas.clear();
         m_supportBrimAreas.clear();
         m_first_layer_convex_hull.points.clear();
         for (PrintObject *object : m_objects)  object->m_skirt.clear();
 
-        const bool draft_shield = config().draft_shield != dsDisabled;
-
-        if (this->has_skirt() && draft_shield) {
-            // In case that draft shield is active, generate skirt first so brim
-            // can be trimmed to make room for it.
-            _make_skirt();
-        }
-
         //BBS: get the objects' indices when GCodes are generated
         ToolOrdering tool_ordering;
         unsigned int initial_extruder_id = (unsigned int)-1;
@@ -2548,11 +2541,16 @@ void Print::process(long long *time_cost_with_cache, bool use_cache)
         }
 
 
-        if (has_skirt() && ! draft_shield) {
-            // In case that draft shield is NOT active, generate skirt now.
-            // It will be placed around the brim, so brim has to be ready.
+        if (has_skirt() || has_infinite_skirt() || has_brim()) {
+            // Generate skirt/brim groups after brim so per-object and draft-shield footprints
+            // include brims when grouping and offsetting skirt loops.
             assert(m_skirt.empty());
             _make_skirt();
+            if (m_config.print_sequence == PrintSequence::ByObject &&
+                m_config.skirt_type == stPerObject &&
+                this->has_shared_per_object_skirt()) {
+                throw Slic3r::SlicingError(L("Per-object skirts cannot fit between the objects in By object print sequence.\n\nMove the objects farther apart, reduce brim/skirt size, switch Skirt type to Combined, or switch Print sequence to By layer."));
+            }
         }
 
         this->finalize_first_layer_convex_hull();
@@ -2644,6 +2642,8 @@ std::string Print::export_gcode(const std::string& path_template, GCodeProcessor
 
 void Print::_make_skirt()
 {
+    const bool generate_skirt = this->has_skirt() || this->has_infinite_skirt();
+
     // First off we need to decide how tall the skirt must be.
     // The skirt_height option from config is expressed in layers, but our
     // object might have different layer heights, so we need to find the print_z
@@ -2655,11 +2655,13 @@ void Print::_make_skirt()
     // prepended to the first 'n' layers (with 'n' = skirt_height).
     // $skirt_height_z in this case is the highest possible skirt height for safety.
     coordf_t skirt_height_z = 0.;
-    for (const PrintObject *object : m_objects) {
-        size_t skirt_layers = this->has_infinite_skirt() ?
-            object->layer_count() :
-            std::min(size_t(m_config.skirt_height.value), object->layer_count());
-        skirt_height_z = std::max(skirt_height_z, object->m_layers[skirt_layers-1]->print_z);
+    if (generate_skirt) {
+        for (const PrintObject *object : m_objects) {
+            size_t skirt_layers = this->has_infinite_skirt() ?
+                object->layer_count() :
+                std::min(size_t(m_config.skirt_height.value), object->layer_count());
+            skirt_height_z = std::max(skirt_height_z, object->m_layers[skirt_layers-1]->print_z);
+        }
     }
 
     struct ObjectSkirtHull {
@@ -2673,7 +2675,7 @@ void Print::_make_skirt()
         Points object_points;
         // Get object layers up to skirt_height_z.
         for (const Layer *layer : object->m_layers) {
-            if (layer->print_z > skirt_height_z)
+            if (generate_skirt && layer->print_z > skirt_height_z)
                 break;
             for (const ExPolygon &expoly : layer->lslices)
                 // Collect the outer contour points only, ignore holes for the calculation of the convex hull.
@@ -2681,7 +2683,7 @@ void Print::_make_skirt()
         }
         // Get support layers up to skirt_height_z.
         for (const SupportLayer *layer : object->support_layers()) {
-            if (layer->print_z > skirt_height_z)
+            if (generate_skirt && layer->print_z > skirt_height_z)
                 break;
             layer->support_fills.collect_points(object_points);
         }
@@ -2771,17 +2773,15 @@ void Print::_make_skirt()
     };
 
     m_skirt.clear();
-    m_skirt_groups.clear();
+    m_skirt_brim_groups.clear();
+    m_has_shared_per_object_skirt = false;
+    for (const ObjectSkirtHull& object_hull : object_convex_hulls)
+        object_hull.object->m_skirt.clear();
 
-    if (m_config.skirt_type == stPerObject && m_config.print_sequence == PrintSequence::ByObject) {
-        for (const ObjectSkirtHull& object_hull : object_convex_hulls) {
-            object_hull.object->m_skirt.clear();
-            append_skirt_loops_for_hull(object_hull.hull, object_hull.object->m_skirt, false);
-            object_hull.object->m_skirt.reverse();
-        }
-    } else if (m_config.skirt_type == stCombined || m_config.skirt_type == stPerObject) {
+    if (m_config.skirt_type == stCombined || m_config.skirt_type == stPerObject) {
         struct SkirtGroupItem {
             Points       occupied_points;
+            ObjectID     object_id;
             bool         emits_skirt;
         };
 
@@ -2811,13 +2811,13 @@ void Print::_make_skirt()
                 continue;
 
             // Orca: include the object's brim/support-brim footprint before checking skirt collisions.
-            group_items.push_back({ std::move(occupied_points), true });
+            group_items.push_back({ std::move(occupied_points), object->id(), true });
         }
 
         // Orca: the wipe tower contributes occupied area, but does not emit a skirt by itself.
         Points wipe_tower_points = this->first_layer_wipe_tower_corners();
         if (wipe_tower_points.size() >= 3)
-            group_items.push_back({ std::move(wipe_tower_points), false });
+            group_items.push_back({ std::move(wipe_tower_points), ObjectID(), false });
 
         std::vector<size_t> parent(group_items.size());
         std::iota(parent.begin(), parent.end(), 0);
@@ -2843,14 +2843,17 @@ void Print::_make_skirt()
 
         auto build_grouped_points = [&]() {
             struct GroupData {
-                Points points;
-                bool   emits_skirt = false;
+                Points                points;
+                std::vector<ObjectID> object_ids;
+                bool                  emits_skirt = false;
             };
 
             std::map<size_t, GroupData> grouped;
             for (size_t i = 0; i < group_items.size(); ++i) {
                 GroupData& group = grouped[find_parent(i)];
                 append(group.points, group_items[i].occupied_points);
+                if (group_items[i].object_id.valid())
+                    group.object_ids.push_back(group_items[i].object_id);
                 group.emits_skirt = group.emits_skirt || group_items[i].emits_skirt;
             }
             return grouped;
@@ -2889,19 +2892,99 @@ void Print::_make_skirt()
             }
         }
 
+        auto make_group_brims = [this](const std::vector<ObjectID>& group_object_ids) {
+            std::vector<SkirtBrimGroup::Brim> brims;
+            std::vector<ObjectID> brim_object_ids;
+            for (ObjectID object_id : group_object_ids) {
+                const auto brim_it = m_brimMap.find(object_id);
+                if (brim_it != m_brimMap.end() && !brim_it->second.empty())
+                    brim_object_ids.push_back(object_id);
+            }
+
+            const bool global_combined_brim = m_config.combine_brims && m_config.skirt_type != stPerObject && m_brimMap.size() == 1;
+            auto brim_owner_ids = [&group_object_ids, global_combined_brim](const std::vector<ObjectID>& object_ids) {
+                return global_combined_brim ? group_object_ids : object_ids;
+            };
+
+            const bool combine_group_brims = m_config.combine_brims && brim_object_ids.size() > 1;
+            if (!combine_group_brims) {
+                for (ObjectID object_id : brim_object_ids)
+                    brims.push_back({ m_brimMap.at(object_id), brim_owner_ids({ object_id }) });
+                return brims;
+            }
+
+            std::vector<size_t> brim_parent(brim_object_ids.size());
+            std::iota(brim_parent.begin(), brim_parent.end(), 0);
+            auto find_brim_parent = [&brim_parent](size_t idx) {
+                while (brim_parent[idx] != idx) {
+                    brim_parent[idx] = brim_parent[brim_parent[idx]];
+                    idx = brim_parent[idx];
+                }
+                return idx;
+            };
+            auto unite_brims = [&brim_parent, &find_brim_parent](size_t a, size_t b) {
+                a = find_brim_parent(a);
+                b = find_brim_parent(b);
+                if (a != b)
+                    brim_parent[b] = a;
+            };
+
+            const coord_t brim_contact_distance = coord_t(brim_flow().scaled_spacing() * 2.);
+            for (size_t i = 0; i < brim_object_ids.size(); ++i) {
+                const auto area_i = m_objectBrimAreas.find(brim_object_ids[i]);
+                if (area_i == m_objectBrimAreas.end())
+                    continue;
+                for (size_t j = i + 1; j < brim_object_ids.size(); ++j) {
+                    const auto area_j = m_objectBrimAreas.find(brim_object_ids[j]);
+                    if (area_j != m_objectBrimAreas.end() &&
+                        !intersection_ex(offset_ex(area_i->second, brim_contact_distance, jtRound, SCALED_RESOLUTION), area_j->second).empty())
+                        unite_brims(i, j);
+                }
+            }
+
+            std::map<size_t, std::vector<ObjectID>> combined_brim_ids;
+            for (size_t i = 0; i < brim_object_ids.size(); ++i)
+                combined_brim_ids[find_brim_parent(i)].push_back(brim_object_ids[i]);
+
+            for (const auto& [_, object_ids] : combined_brim_ids) {
+                if (object_ids.size() == 1) {
+                    brims.push_back({ m_brimMap.at(object_ids.front()), brim_owner_ids(object_ids) });
+                    continue;
+                }
+
+                ExPolygons combined_area;
+                for (ObjectID object_id : object_ids)
+                    expolygons_append(combined_area, m_objectBrimAreas.at(object_id));
+                combined_area = union_ex(combined_area);
+                const float scaled_resolution  = float(scaled(m_config.resolution.value));
+                const float brim_cleanup_delta = std::max(scaled_resolution, float(SCALED_EPSILON));
+                combined_area = offset2_ex(combined_area, brim_cleanup_delta, -brim_cleanup_delta, jtRound, scaled_resolution);
+
+                Polygons islands_area;
+                brims.push_back({ makeBrimInfillFromPlateCoordinates(combined_area, *this, islands_area), object_ids });
+            }
+
+            return brims;
+        };
+
         auto grouped_points = build_grouped_points();
         for (auto& [_, group] : grouped_points) {
             if (!group.emits_skirt || group.points.size() < 3)
                 continue;
+            if (generate_skirt && m_config.skirt_type == stPerObject && group.object_ids.size() > 1)
+                m_has_shared_per_object_skirt = true;
             // Orca: after merging, use the occupied outline directly; do not add skirt distance twice.
             ExtrusionEntityCollection group_skirt;
-            append_skirt_loops_for_hull(Geometry::convex_hull(group.points), group_skirt, true);
+            if (generate_skirt)
+                append_skirt_loops_for_hull(Geometry::convex_hull(group.points), group_skirt, true);
+            std::vector<SkirtBrimGroup::Brim> group_brims = make_group_brims(group.object_ids);
             if (!group_skirt.empty()) {
                 group_skirt.reverse();
                 // Orca: keep m_skirt as a flattened compatibility mirror for preview/extents.
                 m_skirt.append(group_skirt.entities);
-                m_skirt_groups.push_back(std::move(group_skirt));
             }
+            if (!group_skirt.empty() || !group_brims.empty())
+                m_skirt_brim_groups.push_back({ std::move(group_skirt), std::move(group.object_ids), std::move(group_brims) });
         }
     }
 }

src/libslic3r/Print.hpp

@@ -970,8 +970,21 @@ public:
     PrintObjectPtrs&            objects_mutable() { return m_objects; }
     PrintRegionPtrs&            print_regions_mutable() { return m_print_regions; }
     std::vector<size_t>         layers_sorted_for_object(float start, float end, std::vector<LayerPtrs> &layers_of_objects, std::vector<BoundingBox> &boundingBox_for_objects, VecOfPoints& objects_instances_shift);
+    struct SkirtBrimGroup {
+        struct Brim {
+            ExtrusionEntityCollection brim;
+            std::vector<ObjectID>     object_ids;
+        };
+
+        ExtrusionEntityCollection skirt;
+        std::vector<ObjectID>     object_ids;
+        // Brims stay separate unless Combine brims merges colliding brims inside this group.
+        std::vector<Brim>         brims;
+    };
+
     const ExtrusionEntityCollection& skirt() const { return m_skirt; }
-    const std::vector<ExtrusionEntityCollection>& skirt_groups() const { return m_skirt_groups; }
+    const std::vector<SkirtBrimGroup>& skirt_brim_groups() const { return m_skirt_brim_groups; }
+    bool has_shared_per_object_skirt() const { return m_has_shared_per_object_skirt; }
     // Convex hull of the 1st layer extrusions, for bed leveling and placing the initial purge line.
     // It encompasses the object extrusions, support extrusions, skirt, brim, wipe tower.
     // It does NOT encompass user extrusions generated by custom G-code,
@@ -1145,7 +1158,8 @@ private:
 
     // Ordered collections of extrusion paths to build skirt loops and brim.
     ExtrusionEntityCollection               m_skirt;
-    std::vector<ExtrusionEntityCollection>  m_skirt_groups;
+    std::vector<SkirtBrimGroup>             m_skirt_brim_groups;
+    bool                                    m_has_shared_per_object_skirt { false };
     // BBS: collecting extrusion paths to build brim by objs
     std::map<ObjectID, ExtrusionEntityCollection>         m_brimMap;
     std::map<ObjectID, ExtrusionEntityCollection>         m_supportBrimMap;