Fix seam object for multiple instances with different rotations

supermerill/SuperSlicer#2015

src/libslic3r/GCode.cpp

@@ -2230,6 +2230,8 @@ void GCode::process_layer(
     assert(! layers.empty());
     // Either printing all copies of all objects, or just a single copy of a single object.
     assert(single_object_instance_idx == size_t(-1) || layers.size() == 1);
+    if(single_object_instance_idx != size_t(-1))
+        m_print_object_instance_id = static_cast<uint16_t>(single_object_instance_idx);
 
     if (layer_tools.extruders.empty())
         // Nothing to extrude.
@@ -2626,6 +2628,7 @@ void GCode::process_layer(
             for (InstanceToPrint &instance_to_print : instances_to_print) {
                 m_config.apply(instance_to_print.print_object.config(), true);
                 m_layer = layers[instance_to_print.layer_id].layer();
+                m_print_object_instance_id = static_cast<uint16_t>(instance_to_print.instance_id);
                 if (m_config.avoid_crossing_perimeters)
                     m_avoid_crossing_perimeters.init_layer(*m_layer);
                 //print object label to help the printer firmware know where it is (for removing the objects)
@@ -3200,7 +3203,9 @@ void GCode::split_at_seam_pos(ExtrusionLoop& loop, std::unique_ptr<EdgeGrid::Gri
         Point seam = m_seam_placer.get_seam(*m_layer, seam_position, loop,
             last_pos, EXTRUDER_CONFIG_WITH_DEFAULT(nozzle_diameter, 0),
             (m_layer == NULL ? nullptr : m_layer->object()),
-            was_clockwise, edge_grid_ptr);
+            m_print_object_instance_id,
+            was_clockwise,
+            edge_grid_ptr);
         // Split the loop at the point with a minium penalty.
         if (!loop.split_at_vertex(seam))
             // The point is not in the original loop. Insert it.

src/libslic3r/GCode.hpp

@@ -362,6 +362,8 @@ private:
     // Current layer processed. Insequential printing mode, only a single copy will be printed.
     // In non-sequential mode, all its copies will be printed.
     const Layer*                        m_layer;
+    // idx of the current instance printed. (or the last one)
+    uint16_t                            m_print_object_instance_id = -1;
     // For crossing perimeter retraction detection  (contain the layer & nozzle widdth used to construct it)
     // !!!! not thread-safe !!!! if threaded per layer, please store it in the thread.
     struct SliceOffsetted {

src/libslic3r/GCode/SeamPlacer.cpp

@@ -293,7 +293,8 @@ void SeamPlacer::init(const Print& print)
 
 Point SeamPlacer::get_seam(const Layer& layer, SeamPosition seam_position,
                const ExtrusionLoop& loop, Point last_pos, coordf_t nozzle_dmr,
-               const PrintObject* po, bool was_clockwise, const EdgeGrid::Grid* lower_layer_edge_grid)
+               const PrintObject* po, const uint16_t print_object_instance_idx,
+               bool was_clockwise, const EdgeGrid::Grid* lower_layer_edge_grid)
 {
     Polygon polygon = loop.polygon();
     BoundingBox polygon_bb = polygon.bounding_box();
@@ -329,6 +330,7 @@ Point SeamPlacer::get_seam(const Layer& layer, SeamPosition seam_position,
     }
 
     bool has_seam_custom = false;
+    if(print_object_instance_idx < po->instances().size())
         for (ModelVolume* v : po->model_object()->volumes)
             if (v->is_seam_position()) {
                 has_seam_custom = true;
@@ -340,11 +342,13 @@ Point SeamPlacer::get_seam(const Layer& layer, SeamPosition seam_position,
         Vec3d lambda_pos;
         double lambda_dist;
         double lambda_radius;
-        for (ModelVolume* v : po->model_object()->volumes)
+        //get model_instance (like from po->model_object()->instances, but we don't have the index for that array)
+        const ModelInstance* model_instance = po->instances()[print_object_instance_idx].model_instance;
+        for (ModelVolume* v : po->model_object()->volumes) {
             if (v->is_seam_position()) {
                 //xy in object coordinates, z in plater coordinates
-                Vec3d test_lambda_pos = po->model_object()->instances.front()->transform_vector(v->get_offset(), true);
+                Vec3d test_lambda_pos = model_instance->transform_vector(v->get_offset(), true);
-                Vec3d test_lambda_pos_plater = po->model_object()->instances.front()->transform_vector(v->get_offset(), false);
+
                 Point xy_lambda(scale_(test_lambda_pos.x()), scale_(test_lambda_pos.y()));
                 Point nearest = polygon.point_projection(xy_lambda);
                 Vec3d polygon_3dpoint{ unscaled(nearest.x()), unscaled(nearest.y()), (double)layer.print_z };
@@ -361,9 +365,10 @@ Point SeamPlacer::get_seam(const Layer& layer, SeamPosition seam_position,
                     lambda_dist = test_lambda_dist;
                 }
             }
+        }
 
         if (v_lambda_seam != nullptr) {
-            lambda_pos = po->model_object()->instances.front()->transform_vector(v_lambda_seam->get_offset(), true);
+            lambda_pos = model_instance->transform_vector(v_lambda_seam->get_offset(), true);
             // Found, get the center point and apply rotation and scaling of Model instance. Continues to spAligned if not found or Weight set to Zero.
             last_pos = Point::new_scale(lambda_pos.x(), lambda_pos.y());
             // Weight is set by user and stored in the radius of the sphere

src/libslic3r/GCode/SeamPlacer.hpp

@@ -43,7 +43,7 @@ public:
 
     Point get_seam(const Layer& layer, SeamPosition seam_position,
                    const ExtrusionLoop& loop, Point last_pos,
-                   coordf_t nozzle_diameter, const PrintObject* po,
+                   coordf_t nozzle_diameter, const PrintObject* po, const uint16_t object_instance_idx,
                    bool was_clockwise, const EdgeGrid::Grid* lower_layer_edge_grid);
 
     using TreeType = AABBTreeIndirect::Tree<2, coord_t>;