Merge branch 'master' of https://github.com/prusa3d/PrusaSlicer into et_3dconnexion

src/admesh/stl.h

@@ -89,33 +89,34 @@ struct stl_neighbors {
 };
 
 struct stl_stats {
-	stl_stats() { this->reset(); }
+    stl_stats() { memset(&header, 0, 81); }
-	void reset() { memset(this, 0, sizeof(stl_stats)); this->volume = -1.0; }
     char          header[81];
-	stl_type      type;
+    stl_type      type                      = (stl_type)0;
-	uint32_t      number_of_facets;
+    uint32_t      number_of_facets          = 0;
-	stl_vertex    max;
+    stl_vertex    max                       = stl_vertex::Zero();
-	stl_vertex    min;
+    stl_vertex    min                       = stl_vertex::Zero();
-	stl_vertex    size;
+    stl_vertex    size                      = stl_vertex::Zero();
-	float         bounding_diameter;
+    float         bounding_diameter         = 0.f;
-	float         shortest_edge;
+    float         shortest_edge             = 0.f;
-	float         volume;
+    float         volume                    = -1.f;
-	int           connected_edges;
+    int           connected_edges           = 0;
-	int           connected_facets_1_edge;
+    int           connected_facets_1_edge   = 0;
-	int           connected_facets_2_edge;
+    int           connected_facets_2_edge   = 0;
-	int           connected_facets_3_edge;
+    int           connected_facets_3_edge   = 0;
-	int           facets_w_1_bad_edge;
+    int           facets_w_1_bad_edge       = 0;
-	int           facets_w_2_bad_edge;
+    int           facets_w_2_bad_edge       = 0;
-	int           facets_w_3_bad_edge;
+    int           facets_w_3_bad_edge       = 0;
-	int           original_num_facets;
+    int           original_num_facets       = 0;
-	int           edges_fixed;
+    int           edges_fixed               = 0;
-	int           degenerate_facets;
+    int           degenerate_facets         = 0;
-	int           facets_removed;
+    int           facets_removed            = 0;
-	int           facets_added;
+    int           facets_added              = 0;
-	int           facets_reversed;
+    int           facets_reversed           = 0;
-	int           backwards_edges;
+    int           backwards_edges           = 0;
-	int           normals_fixed;
+    int           normals_fixed             = 0;
-	int           number_of_parts;
+    int           number_of_parts           = 0;
+
+    void clear() { *this = stl_stats(); }
 };
 
 struct stl_file {
@@ -124,7 +125,7 @@ struct stl_file {
 	void clear() {
 		this->facet_start.clear();
 		this->neighbors_start.clear();
-		this->stats.reset();
+        this->stats.clear();
 	}
 
 	size_t memsize() const {

src/clipper/clipper_z.hpp

@@ -15,4 +15,4 @@
 #undef clipper_hpp
 #undef use_xyz
 
-#endif clipper_z_hpp
+#endif // clipper_z_hpp

src/libslic3r/CMakeLists.txt

@@ -100,7 +100,7 @@ add_library(libslic3r STATIC
     Geometry.cpp
     Geometry.hpp
     Int128.hpp
-#    KdTree.hpp
+    KDTreeIndirect.hpp
     Layer.cpp
     Layer.hpp
     LayerRegion.cpp
@@ -142,6 +142,8 @@ add_library(libslic3r STATIC
     PrintObject.cpp
     PrintRegion.cpp
     Semver.cpp
+    ShortestPath.cpp
+    ShortestPath.hpp
     SLAPrint.cpp
     SLAPrint.hpp
     SLA/SLAAutoSupports.hpp

src/libslic3r/ClipperUtils.cpp

@@ -1,5 +1,6 @@
 #include "ClipperUtils.hpp"
 #include "Geometry.hpp"
+#include "ShortestPath.hpp"
 
 // #define CLIPPER_UTILS_DEBUG
 
@@ -671,21 +672,19 @@ void traverse_pt(ClipperLib::PolyNodes &nodes, Polygons* retval)
     // collect ordering points
     Points ordering_points;
     ordering_points.reserve(nodes.size());
-    for (ClipperLib::PolyNodes::const_iterator it = nodes.begin(); it != nodes.end(); ++it) {
+    for (ClipperLib::PolyNode *pn : nodes)
-        Point p((*it)->Contour.front().X, (*it)->Contour.front().Y);
+        ordering_points.emplace_back(Point(pn->Contour.front().X, pn->Contour.front().Y));
-        ordering_points.emplace_back(p);
-    }
     
     // perform the ordering
-    ClipperLib::PolyNodes ordered_nodes;
+    ClipperLib::PolyNodes ordered_nodes = chain_clipper_polynodes(ordering_points, nodes);
-    Slic3r::Geometry::chained_path_items(ordering_points, nodes, ordered_nodes);
 
     // push results recursively
-    for (ClipperLib::PolyNodes::iterator it = ordered_nodes.begin(); it != ordered_nodes.end(); ++it) {
+    for (ClipperLib::PolyNode *pn : ordered_nodes) {
         // traverse the next depth
-        traverse_pt((*it)->Childs, retval);
+        traverse_pt(pn->Childs, retval);
-        retval->emplace_back(ClipperPath_to_Slic3rPolygon((*it)->Contour));
+        retval->emplace_back(ClipperPath_to_Slic3rPolygon(pn->Contour));
-        if ((*it)->IsHole()) retval->back().reverse();  // ccw
+        if (pn->IsHole())
+        	retval->back().reverse(); // ccw
     }
 }
 

src/libslic3r/ExtrusionEntity.hpp

@@ -5,6 +5,8 @@
 #include "Polygon.hpp"
 #include "Polyline.hpp"
 
+#include <assert.h>
+
 namespace Slic3r {
 
 class ExPolygonCollection;

src/libslic3r/ExtrusionEntityCollection.cpp

@@ -16,7 +16,6 @@ ExtrusionEntityCollection& ExtrusionEntityCollection::operator=(const ExtrusionE
     this->entities      = other.entities;
     for (size_t i = 0; i < this->entities.size(); ++i)
         this->entities[i] = this->entities[i]->clone();
-    this->orig_indices  = other.orig_indices;
     this->no_sort       = other.no_sort;
     return *this;
 }
@@ -24,7 +23,6 @@ ExtrusionEntityCollection& ExtrusionEntityCollection::operator=(const ExtrusionE
 void ExtrusionEntityCollection::swap(ExtrusionEntityCollection &c)
 {
     std::swap(this->entities, c.entities);
-    std::swap(this->orig_indices, c.orig_indices);
     std::swap(this->no_sort, c.no_sort);
 }
 
@@ -82,10 +80,10 @@ ExtrusionEntityCollection ExtrusionEntityCollection::chained_path(bool no_revers
     return coll;
 }
 
-void ExtrusionEntityCollection::chained_path(ExtrusionEntityCollection* retval, bool no_reverse, ExtrusionRole role, std::vector<size_t>* orig_indices) const
+void ExtrusionEntityCollection::chained_path(ExtrusionEntityCollection* retval, bool no_reverse, ExtrusionRole role) const
 {
     if (this->entities.empty()) return;
-    this->chained_path_from(this->entities.front()->first_point(), retval, no_reverse, role, orig_indices);
+    this->chained_path_from(this->entities.front()->first_point(), retval, no_reverse, role);
 }
 
 ExtrusionEntityCollection ExtrusionEntityCollection::chained_path_from(Point start_near, bool no_reverse, ExtrusionRole role) const
@@ -95,7 +93,7 @@ ExtrusionEntityCollection ExtrusionEntityCollection::chained_path_from(Point sta
     return coll;
 }
 
-void ExtrusionEntityCollection::chained_path_from(Point start_near, ExtrusionEntityCollection* retval, bool no_reverse, ExtrusionRole role, std::vector<size_t>* orig_indices) const
+void ExtrusionEntityCollection::chained_path_from(Point start_near, ExtrusionEntityCollection* retval, bool no_reverse, ExtrusionRole role) const
 {
     if (this->no_sort) {
         *retval = *this;
@@ -103,7 +101,6 @@ void ExtrusionEntityCollection::chained_path_from(Point start_near, ExtrusionEnt
     }
 
     retval->entities.reserve(this->entities.size());
-    retval->orig_indices.reserve(this->entities.size());
     
     // if we're asked to return the original indices, build a map
     std::map<ExtrusionEntity*,size_t> indices_map;
@@ -122,8 +119,8 @@ void ExtrusionEntityCollection::chained_path_from(Point start_near, ExtrusionEnt
 
         ExtrusionEntity *entity = entity_src->clone();
         my_paths.push_back(entity);
-        if (orig_indices != nullptr)
+//        if (orig_indices != nullptr)
-        	indices_map[entity] = &entity_src - &this->entities.front();
+//        	indices_map[entity] = &entity_src - &this->entities.front();
     }
     
     Points endpoints;
@@ -142,8 +139,8 @@ void ExtrusionEntityCollection::chained_path_from(Point start_near, ExtrusionEnt
         if (start_index % 2 && !no_reverse && entity->can_reverse())
             entity->reverse();
         retval->entities.push_back(my_paths.at(path_index));
-        if (orig_indices != nullptr)
+//        if (orig_indices != nullptr)
-        	orig_indices->push_back(indices_map[entity]);
+//        	orig_indices->push_back(indices_map[entity]);
         my_paths.erase(my_paths.begin() + path_index);
         endpoints.erase(endpoints.begin() + 2*path_index, endpoints.begin() + 2*path_index + 2);
         start_near = retval->entities.back()->last_point();

src/libslic3r/ExtrusionEntityCollection.hpp

@@ -14,15 +14,14 @@ public:
 	ExtrusionEntity* clone_move() override { return new ExtrusionEntityCollection(std::move(*this)); }
 
     ExtrusionEntitiesPtr entities;     // we own these entities
-    std::vector<size_t> orig_indices;  // handy for XS
     bool no_sort;
     ExtrusionEntityCollection(): no_sort(false) {};
-    ExtrusionEntityCollection(const ExtrusionEntityCollection &other) : orig_indices(other.orig_indices), no_sort(other.no_sort) { this->append(other.entities); }
+    ExtrusionEntityCollection(const ExtrusionEntityCollection &other) : no_sort(other.no_sort) { this->append(other.entities); }
-    ExtrusionEntityCollection(ExtrusionEntityCollection &&other) : entities(std::move(other.entities)), orig_indices(std::move(other.orig_indices)), no_sort(other.no_sort) {}
+    ExtrusionEntityCollection(ExtrusionEntityCollection &&other) : entities(std::move(other.entities)), no_sort(other.no_sort) {}
     explicit ExtrusionEntityCollection(const ExtrusionPaths &paths);
     ExtrusionEntityCollection& operator=(const ExtrusionEntityCollection &other);
     ExtrusionEntityCollection& operator=(ExtrusionEntityCollection &&other) 
-        { this->entities = std::move(other.entities); this->orig_indices = std::move(other.orig_indices); this->no_sort = other.no_sort; return *this; }
+        { this->entities = std::move(other.entities); this->no_sort = other.no_sort; return *this; }
     ~ExtrusionEntityCollection() { clear(); }
     explicit operator ExtrusionPaths() const;
     
@@ -67,9 +66,9 @@ public:
     void replace(size_t i, const ExtrusionEntity &entity);
     void remove(size_t i);
     ExtrusionEntityCollection chained_path(bool no_reverse = false, ExtrusionRole role = erMixed) const;
-    void chained_path(ExtrusionEntityCollection* retval, bool no_reverse = false, ExtrusionRole role = erMixed, std::vector<size_t>* orig_indices = nullptr) const;
+    void chained_path(ExtrusionEntityCollection* retval, bool no_reverse = false, ExtrusionRole role = erMixed) const;
     ExtrusionEntityCollection chained_path_from(Point start_near, bool no_reverse = false, ExtrusionRole role = erMixed) const;
-    void chained_path_from(Point start_near, ExtrusionEntityCollection* retval, bool no_reverse = false, ExtrusionRole role = erMixed, std::vector<size_t>* orig_indices = nullptr) const;
+    void chained_path_from(Point start_near, ExtrusionEntityCollection* retval, bool no_reverse = false, ExtrusionRole role = erMixed) const;
     void reverse();
     Point first_point() const { return this->entities.front()->first_point(); }
     Point last_point() const { return this->entities.back()->last_point(); }

src/libslic3r/Fill/Fill.cpp

@@ -15,40 +15,39 @@ namespace Slic3r {
 
 struct SurfaceFillParams
 {
-	SurfaceFillParams() : flow(0.f, 0.f, 0.f, false) { memset(this, 0, sizeof(*this)); }
 	// Zero based extruder ID.
-	unsigned int 	extruder;
+    unsigned int 	extruder = 0;
 	// Infill pattern, adjusted for the density etc.
-	InfillPattern  	pattern;
+    InfillPattern  	pattern = InfillPattern(0);
 
     // FillBase
     // in unscaled coordinates
-    coordf_t    	spacing;
+    coordf_t    	spacing = 0.;
     // infill / perimeter overlap, in unscaled coordinates
-    coordf_t    	overlap;
+    coordf_t    	overlap = 0.;
     // Angle as provided by the region config, in radians.
-    float       	angle;
+    float       	angle = 0.f;
     // Non-negative for a bridge.
-    float 			bridge_angle;
+    float 			bridge_angle = 0.f;
 
     // FillParams
-    float       	density;
+    float       	density = 0.f;
     // Don't connect the fill lines around the inner perimeter.
-    bool        	dont_connect;
+    bool        	dont_connect = false;
     // Don't adjust spacing to fill the space evenly.
-    bool        	dont_adjust;
+    bool        	dont_adjust = false;
 
     // width, height of extrusion, nozzle diameter, is bridge
     // For the output, for fill generator.
-	Flow 			flow;
+    Flow 			flow = Flow(0.f, 0.f, 0.f, false);
 
 	// For the output
-	ExtrusionRole	extrusion_role;
+    ExtrusionRole	extrusion_role = ExtrusionRole(0);
 
 	// Various print settings?
 
 	// Index of this entry in a linear vector.
-	size_t 			idx;
+    size_t 			idx = 0;
 
 
 	bool operator<(const SurfaceFillParams &rhs) const {

src/libslic3r/Fill/Fill3DHoneycomb.cpp

@@ -1,5 +1,5 @@
 #include "../ClipperUtils.hpp"
-#include "../PolylineCollection.hpp"
+#include "../ShortestPath.hpp"
 #include "../Surface.hpp"
 
 #include "Fill3DHoneycomb.hpp"
@@ -175,27 +175,24 @@ void Fill3DHoneycomb::_fill_surface_single(
                 std::swap(expolygon_off, expolygons_off.front());
             }
         }
-        Polylines chained = PolylineCollection::chained_path_from(
-            std::move(polylines), 
-            PolylineCollection::leftmost_point(polylines), false); // reverse allowed
         bool first = true;
-        for (Polylines::iterator it_polyline = chained.begin(); it_polyline != chained.end(); ++ it_polyline) {
+        for (Polyline &polyline : chain_infill_polylines(std::move(polylines))) {
             if (! first) {
                 // Try to connect the lines.
                 Points &pts_end = polylines_out.back().points;
-                const Point &first_point = it_polyline->points.front();
+                const Point &first_point = polyline.points.front();
                 const Point &last_point = pts_end.back();
                 // TODO: we should also check that both points are on a fill_boundary to avoid 
                 // connecting paths on the boundaries of internal regions
                 if ((last_point - first_point).cast<double>().norm() <= 1.5 * distance && 
                     expolygon_off.contains(Line(last_point, first_point))) {
                     // Append the polyline.
-                    pts_end.insert(pts_end.end(), it_polyline->points.begin(), it_polyline->points.end());
+                    pts_end.insert(pts_end.end(), polyline.points.begin(), polyline.points.end());
                     continue;
                 }
             }
             // The lines cannot be connected.
-            polylines_out.emplace_back(std::move(*it_polyline));
+            polylines_out.emplace_back(std::move(polyline));
             first = false;
         }
     }

src/libslic3r/Fill/FillGyroid.cpp

@@ -1,5 +1,5 @@
 #include "../ClipperUtils.hpp"
-#include "../PolylineCollection.hpp"
+#include "../ShortestPath.hpp"
 #include "../Surface.hpp"
 #include <cmath>
 #include <algorithm>
@@ -166,11 +166,8 @@ void FillGyroid::_fill_surface_single(
                 std::swap(expolygon_off, expolygons_off.front());
             }
         }
-        Polylines chained = PolylineCollection::chained_path_from(
-            std::move(polylines), 
-            PolylineCollection::leftmost_point(polylines), false); // reverse allowed
         bool first = true;
-        for (Polyline &polyline : chained) {
+        for (Polyline &polyline : chain_infill_polylines(std::move(polylines))) {
             if (! first) {
                 // Try to connect the lines.
                 Points &pts_end = polylines_out.back().points;

src/libslic3r/Fill/FillHoneycomb.cpp

@@ -1,5 +1,5 @@
 #include "../ClipperUtils.hpp"
-#include "../PolylineCollection.hpp"
+#include "../ShortestPath.hpp"
 #include "../Surface.hpp"
 
 #include "FillHoneycomb.hpp"
@@ -93,22 +93,20 @@ void FillHoneycomb::_fill_surface_single(
 
         // connect paths
         if (! paths.empty()) { // prevent calling leftmost_point() on empty collections
-            Polylines chained = PolylineCollection::chained_path_from(
+            Polylines chained = chain_infill_polylines(std::move(paths));
-                std::move(paths), 
-                PolylineCollection::leftmost_point(paths), false);
             assert(paths.empty());
             paths.clear();
-            for (Polylines::iterator it_path = chained.begin(); it_path != chained.end(); ++ it_path) {
+            for (Polyline &path : chained) {
                 if (! paths.empty()) {
                     // distance between first point of this path and last point of last path
-                    double distance = (it_path->first_point() - paths.back().last_point()).cast<double>().norm();
+                    double distance = (path.first_point() - paths.back().last_point()).cast<double>().norm();
                     if (distance <= m.hex_width) {
-                        paths.back().points.insert(paths.back().points.end(), it_path->points.begin(), it_path->points.end());
+                        paths.back().points.insert(paths.back().points.end(), path.points.begin(), path.points.end());
                         continue;
                     }
                 }
                 // Don't connect the paths.
-                paths.push_back(*it_path);
+                paths.push_back(std::move(path));
             }
         }
         

src/libslic3r/Fill/FillRectilinear.cpp

@@ -1,6 +1,6 @@
 #include "../ClipperUtils.hpp"
 #include "../ExPolygon.hpp"
-#include "../PolylineCollection.hpp"
+#include "../ShortestPath.hpp"
 #include "../Surface.hpp"
 
 #include "FillRectilinear.hpp"
@@ -92,15 +92,12 @@ void FillRectilinear::_fill_surface_single(
                 std::swap(expolygon_off, expolygons_off.front());
             }
         }
-        Polylines chained = PolylineCollection::chained_path_from(
-            std::move(polylines), 
-            PolylineCollection::leftmost_point(polylines), false); // reverse allowed
         bool first = true;
-        for (Polylines::iterator it_polyline = chained.begin(); it_polyline != chained.end(); ++ it_polyline) {
+        for (Polyline &polyline : chain_infill_polylines(std::move(polylines))) {
             if (! first) {
                 // Try to connect the lines.
                 Points &pts_end = polylines_out.back().points;
-                const Point &first_point = it_polyline->points.front();
+                const Point &first_point = polyline.points.front();
                 const Point &last_point = pts_end.back();
                 // Distance in X, Y.
                 const Vector distance = last_point - first_point;
@@ -109,12 +106,12 @@ void FillRectilinear::_fill_surface_single(
                 if (this->_can_connect(std::abs(distance(0)), std::abs(distance(1))) && 
                     expolygon_off.contains(Line(last_point, first_point))) {
                     // Append the polyline.
-                    pts_end.insert(pts_end.end(), it_polyline->points.begin(), it_polyline->points.end());
+                    pts_end.insert(pts_end.end(), polyline.points.begin(), polyline.points.end());
                     continue;
                 }
             }
             // The lines cannot be connected.
-            polylines_out.emplace_back(std::move(*it_polyline));
+            polylines_out.emplace_back(std::move(polyline));
             first = false;
         }
     }

src/libslic3r/Format/PRUS.cpp

@@ -246,7 +246,7 @@ static void extract_model_from_archive(
                 sscanf(normal_buf[2], "%f", &facet.normal(2)) != 1) {
                 // Normal was mangled. Maybe denormals or "not a number" were stored?
                 // Just reset the normal and silently ignore it.
-                memset(&facet.normal, 0, sizeof(facet.normal));
+                facet.normal = stl_normal::Zero();
             }
             facets.emplace_back(facet);
         }
@@ -278,7 +278,7 @@ static void extract_model_from_archive(
         instance->set_rotation(instance_rotation);
         instance->set_scaling_factor(instance_scaling_factor);
         instance->set_offset(instance_offset);
-        if (group_id != (size_t)-1)
+        if (group_id != (unsigned int)(-1))
             group_to_model_object[group_id] = model_object;
     } else {
         // This is not the 1st mesh of a group. Add it to the ModelObject.

src/libslic3r/GCode.cpp

@@ -6,6 +6,7 @@
 #include "Geometry.hpp"
 #include "GCode/PrintExtents.hpp"
 #include "GCode/WipeTower.hpp"
+#include "ShortestPath.hpp"
 #include "Utils.hpp"
 
 #include <algorithm>
@@ -1160,7 +1161,7 @@ void GCode::_do_export(Print &print, FILE *file)
                 for (const LayerToPrint &ltp : layers_to_print) {
                     std::vector<LayerToPrint> lrs;
                     lrs.emplace_back(std::move(ltp));
-                    this->process_layer(file, print, lrs, tool_ordering.tools_for_layer(ltp.print_z()), &copy - object.copies().data());
+                    this->process_layer(file, print, lrs, tool_ordering.tools_for_layer(ltp.print_z()), nullptr, &copy - object.copies().data());
                     print.throw_if_canceled();
                 }
 #ifdef HAS_PRESSURE_EQUALIZER
@@ -1174,12 +1175,8 @@ void GCode::_do_export(Print &print, FILE *file)
             }
         }
     } else {
-        // Order objects using a nearest neighbor search.
+        // Order object instances using a nearest neighbor search.
-        std::vector<size_t> object_indices;
+        std::vector<std::pair<size_t, size_t>> print_object_instances_ordering = chain_print_object_instances(print);
-        Points object_reference_points;
-        for (PrintObject *object : print.objects())
-            object_reference_points.push_back(object->copies().front());
-        Slic3r::Geometry::chained_path(object_reference_points, object_indices);
         // Sort layers by Z.
         // All extrusion moves with the same top layer height are extruded uninterrupted.
         std::vector<std::pair<coordf_t, std::vector<LayerToPrint>>> layers_to_print = collect_layers_to_print(print);
@@ -1218,7 +1215,7 @@ void GCode::_do_export(Print &print, FILE *file)
             const LayerTools &layer_tools = tool_ordering.tools_for_layer(layer.first);
             if (m_wipe_tower && layer_tools.has_wipe_tower)
                 m_wipe_tower->next_layer();
-            this->process_layer(file, print, layer.second, layer_tools, size_t(-1));
+            this->process_layer(file, print, layer.second, layer_tools, &print_object_instances_ordering, size_t(-1));
             print.throw_if_canceled();
         }
 #ifdef HAS_PRESSURE_EQUALIZER
@@ -1529,8 +1526,54 @@ inline std::vector<GCode::ObjectByExtruder::Island>& object_islands_by_extruder(
     return islands;
 }
 
+std::vector<GCode::InstanceToPrint> GCode::sort_print_object_instances(
+	std::vector<GCode::ObjectByExtruder> 			&objects_by_extruder,
+	const std::vector<LayerToPrint> 				&layers,
+	// Ordering must be defined for normal (non-sequential print).
+	const std::vector<std::pair<size_t, size_t>> 	*ordering,
+	// For sequential print, the instance of the object to be printing has to be defined.
+	const size_t                     				 single_object_instance_idx)
+{
+    std::vector<InstanceToPrint> out;
+
+    if (ordering == nullptr) {
+    	// Sequential print, single object is being printed.
+		for (ObjectByExtruder &object_by_extruder : objects_by_extruder) {
+		    const size_t       layer_id     = &object_by_extruder - objects_by_extruder.data();
+		    const PrintObject *print_object = layers[layer_id].object();
+		    if (print_object)
+		    	out.emplace_back(object_by_extruder, layer_id, *print_object, single_object_instance_idx);
+		}
+    } else {
+		// Create mapping from PrintObject* to ObjectByExtruder*.
+		std::vector<std::pair<const PrintObject*, ObjectByExtruder*>> sorted;
+		sorted.reserve(objects_by_extruder.size());
+		for (ObjectByExtruder &object_by_extruder : objects_by_extruder) {
+		    const size_t       layer_id     = &object_by_extruder - objects_by_extruder.data();
+		    const PrintObject *print_object = layers[layer_id].object();
+		    if (print_object)
+		    	sorted.emplace_back(print_object, &object_by_extruder);
+		}
+		std::sort(sorted.begin(), sorted.end());
+
+		if (! sorted.empty()) {
+			const Print &print = *sorted.front().first->print();
+		    out.reserve(sorted.size());
+		    for (const std::pair<size_t, size_t> &instance_id : *ordering) {
+		    	const PrintObject &print_object = *print.objects()[instance_id.first];
+		    	std::pair<const PrintObject*, ObjectByExtruder*> key(&print_object, nullptr);
+		    	auto it = std::lower_bound(sorted.begin(), sorted.end(), key);
+		    	if (it != sorted.end() && it->first == &print_object)
+		    		// ObjectByExtruder for this PrintObject was found.
+					out.emplace_back(*it->second, it->second - objects_by_extruder.data(), print_object, instance_id.second);
+		    }
+		}
+	}
+	return out;
+}
+
 // In sequential mode, process_layer is called once per each object and its copy, 
-// therefore layers will contain a single entry and single_object_idx will point to the copy of the object.
+// 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.
 // For multi-material prints, this routine minimizes extruder switches by gathering extruder specific extrusion paths
 // and performing the extruder specific extrusions together.
@@ -1541,14 +1584,16 @@ void GCode::process_layer(
     // Set of object & print layers of the same PrintObject and with the same print_z.
     const std::vector<LayerToPrint> &layers,
     const LayerTools                &layer_tools,
+	// Pairs of PrintObject index and its instance index.
+	const std::vector<std::pair<size_t, size_t>> *ordering,
     // If set to size_t(-1), then print all copies of all objects.
     // Otherwise print a single copy of a single object.
-    const size_t                     single_object_idx)
+    const size_t                     single_object_instance_idx)
 {
     assert(! layers.empty());
 //    assert(! layer_tools.extruders.empty());
     // Either printing all copies of all objects, or just a single copy of a single object.
-    assert(single_object_idx == size_t(-1) || layers.size() == 1);
+    assert(single_object_instance_idx == size_t(-1) || layers.size() == 1);
 
     if (layer_tools.extruders.empty())
         // Nothing to extrude.
@@ -1762,6 +1807,17 @@ void GCode::process_layer(
             layer_surface_bboxes.reserve(n_slices);
             for (const ExPolygon &expoly : layer.slices.expolygons)
                 layer_surface_bboxes.push_back(get_extents(expoly.contour));
+            // Traverse the slices in an increasing order of bounding box size, so that the islands inside another islands are tested first,
+            // so we can just test a point inside ExPolygon::contour and we may skip testing the holes.
+            std::vector<size_t> slices_test_order;
+            slices_test_order.reserve(n_slices);
+            for (size_t i = 0; i < n_slices; ++ i)
+            	slices_test_order.emplace_back(i);
+            std::sort(slices_test_order.begin(), slices_test_order.end(), [&layer_surface_bboxes](int i, int j) {
+            	const Vec2d s1 = layer_surface_bboxes[i].size().cast<double>();
+            	const Vec2d s2 = layer_surface_bboxes[j].size().cast<double>();
+            	return s1.x() * s1.y() < s2.x() * s2.y();
+            });
             auto point_inside_surface = [&layer, &layer_surface_bboxes](const size_t i, const Point &point) { 
                 const BoundingBox &bbox = layer_surface_bboxes[i];
                 return point(0) >= bbox.min(0) && point(0) < bbox.max(0) &&
@@ -1809,20 +1865,23 @@ void GCode::process_layer(
                                     extruder,
                                     &layer_to_print - layers.data(),
                                     layers.size(), n_slices+1);
-                                for (size_t i = 0; i <= n_slices; ++i)
+                                for (size_t i = 0; i <= n_slices; ++ i) {
+									bool   last = i == n_slices;
+                                	size_t island_idx = last ? n_slices : slices_test_order[i];
                                     if (// fill->first_point does not fit inside any slice
-                                        i == n_slices ||
+										last ||
                                         // fill->first_point fits inside ith slice
-                                        point_inside_surface(i, fill->first_point())) {
+                                        point_inside_surface(island_idx, fill->first_point())) {
-                                        if (islands[i].by_region.empty())
+                                        if (islands[island_idx].by_region.empty())
-                                            islands[i].by_region.assign(print.regions().size(), ObjectByExtruder::Island::Region());
+                                            islands[island_idx].by_region.assign(print.regions().size(), ObjectByExtruder::Island::Region());
-                                        islands[i].by_region[region_id].append(entity_type, fill, entity_overrides, layer_to_print.object()->copies().size());
+                                        islands[island_idx].by_region[region_id].append(entity_type, fill, entity_overrides, layer_to_print.object()->copies().size());
                                         break;
                                     }
                                 }
                             }
                         }
                     }
+                }
             } // for regions
         }
     } // for objects
@@ -1883,62 +1942,49 @@ void GCode::process_layer(
         if (objects_by_extruder_it == by_extruder.end())
             continue;
 
+		std::vector<InstanceToPrint> instances_to_print = sort_print_object_instances(objects_by_extruder_it->second, layers, ordering, single_object_instance_idx);
+
         // 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):
         bool is_anything_overridden = const_cast<LayerTools&>(layer_tools).wiping_extrusions().is_anything_overridden();
         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";
 
-            for (ObjectByExtruder &object_by_extruder : objects_by_extruder_it->second) {
+            for (InstanceToPrint &instance_to_print : instances_to_print) {
-                const size_t       layer_id     = &object_by_extruder - objects_by_extruder_it->second.data();
+                m_config.apply(instance_to_print.print_object.config(), true);
-                const PrintObject *print_object = layers[layer_id].object();
+                m_layer = layers[instance_to_print.layer_id].layer();
-                if (print_object == nullptr)
-                    // This layer is empty for this particular object, it has neither object extrusions nor support extrusions at this print_z.
-                    continue;
-
-                m_config.apply(print_object->config(), true);
-                m_layer = layers[layer_id].layer();
                 if (m_config.avoid_crossing_perimeters)
                     m_avoid_crossing_perimeters.init_layer_mp(union_ex(m_layer->slices, true));
-                Points copies;
-                if (single_object_idx == size_t(-1))
-                    copies = print_object->copies();
-                else
-                    copies.push_back(print_object->copies()[single_object_idx]);
-                // Sort the copies by the closest point starting with the current print position.
 
-                unsigned int copy_id = 0;
-                for (const Point &copy : copies) {
                 if (this->config().gcode_label_objects)
-                        gcode += std::string("; printing object ") + print_object->model_object()->name + " id:" + std::to_string(layer_id) + " copy " + std::to_string(copy_id) + "\n";
+                    gcode += std::string("; printing object ") + instance_to_print.print_object.model_object()->name + " id:" + std::to_string(instance_to_print.layer_id) + " copy " + std::to_string(instance_to_print.instance_id) + "\n";
                 // When starting a new object, use the external motion planner for the first travel move.
-                    std::pair<const PrintObject*, Point> this_object_copy(print_object, copy);
+                const Point &offset = instance_to_print.print_object.copies()[instance_to_print.instance_id];
+                std::pair<const PrintObject*, Point> this_object_copy(&instance_to_print.print_object, offset);
                 if (m_last_obj_copy != this_object_copy)
                     m_avoid_crossing_perimeters.use_external_mp_once = true;
                 m_last_obj_copy = this_object_copy;
-                    this->set_origin(unscale(copy));
+                this->set_origin(unscale(offset));
-                    if (object_by_extruder.support != nullptr && !print_wipe_extrusions) {
+                if (instance_to_print.object_by_extruder.support != nullptr && !print_wipe_extrusions) {
-                        m_layer = layers[layer_id].support_layer;
+                    m_layer = layers[instance_to_print.layer_id].support_layer;
                     gcode += this->extrude_support(
                         // support_extrusion_role is erSupportMaterial, erSupportMaterialInterface or erMixed for all extrusion paths.
-                            object_by_extruder.support->chained_path_from(m_last_pos, false, object_by_extruder.support_extrusion_role));
+                        instance_to_print.object_by_extruder.support->chained_path_from(m_last_pos, false, instance_to_print.object_by_extruder.support_extrusion_role));
-                        m_layer = layers[layer_id].layer();
+                    m_layer = layers[instance_to_print.layer_id].layer();
                 }
-                    for (ObjectByExtruder::Island &island : object_by_extruder.islands) {
+                for (ObjectByExtruder::Island &island : instance_to_print.object_by_extruder.islands) {
-                        const auto& by_region_specific = is_anything_overridden ? island.by_region_per_copy(copy_id, extruder_id, print_wipe_extrusions) : island.by_region;
+                    const auto& by_region_specific = is_anything_overridden ? island.by_region_per_copy(instance_to_print.instance_id, extruder_id, print_wipe_extrusions) : island.by_region;
 
                     if (print.config().infill_first) {
                         gcode += this->extrude_infill(print, by_region_specific);
-                            gcode += this->extrude_perimeters(print, by_region_specific, lower_layer_edge_grids[layer_id]);
+                        gcode += this->extrude_perimeters(print, by_region_specific, lower_layer_edge_grids[instance_to_print.layer_id]);
                     } else {
-                            gcode += this->extrude_perimeters(print, by_region_specific, lower_layer_edge_grids[layer_id]);
+                        gcode += this->extrude_perimeters(print, by_region_specific, lower_layer_edge_grids[instance_to_print.layer_id]);
                         gcode += this->extrude_infill(print,by_region_specific);
                     }
                 }
                 if (this->config().gcode_label_objects)
-						gcode += std::string("; stop printing object ") + print_object->model_object()->name + " id:" + std::to_string(layer_id) + " copy " + std::to_string(copy_id) + "\n";
+					gcode += std::string("; stop printing object ") + instance_to_print.print_object.model_object()->name + " id:" + std::to_string(instance_to_print.layer_id) + " copy " + std::to_string(instance_to_print.instance_id) + "\n";
-                    ++ copy_id;
-                }
             }
         }
     }
@@ -2542,12 +2588,10 @@ std::string GCode::extrude_infill(const Print &print, const std::vector<ObjectBy
     std::string gcode;
     for (const ObjectByExtruder::Island::Region &region : by_region) {
         m_config.apply(print.regions()[&region - &by_region.front()]->config());
-		ExtrusionEntityCollection chained = region.infills.chained_path_from(m_last_pos, false);
+        for (ExtrusionEntity *fill : region.infills.chained_path_from(m_last_pos, false).entities) {
-        for (ExtrusionEntity *fill : chained.entities) {
             auto *eec = dynamic_cast<ExtrusionEntityCollection*>(fill);
             if (eec) {
-				ExtrusionEntityCollection chained2 = eec->chained_path_from(m_last_pos, false);
+				for (ExtrusionEntity *ee : eec->chained_path_from(m_last_pos, false).entities)
-				for (ExtrusionEntity *ee : chained2.entities)
                     gcode += this->extrude_entity(*ee, "infill");
             } else
                 gcode += this->extrude_entity(*fill, "infill");

src/libslic3r/GCode.hpp

@@ -202,7 +202,7 @@ protected:
         const PrintObject*    object() const { return (this->layer() != nullptr) ? this->layer()->object() : nullptr; }
         coordf_t              print_z() const { return (object_layer != nullptr && support_layer != nullptr) ? 0.5 * (object_layer->print_z + support_layer->print_z) : this->layer()->print_z; }
     };
-    static std::vector<GCode::LayerToPrint>                            collect_layers_to_print(const PrintObject &object);
+    static std::vector<LayerToPrint>        		                   collect_layers_to_print(const PrintObject &object);
     static std::vector<std::pair<coordf_t, std::vector<LayerToPrint>>> collect_layers_to_print(const Print &print);
     void            process_layer(
         // Write into the output file.
@@ -211,6 +211,8 @@ protected:
         // Set of object & print layers of the same PrintObject and with the same print_z.
         const std::vector<LayerToPrint> &layers,
         const LayerTools  				&layer_tools,
+		// Pairs of PrintObject index and its instance index.
+		const std::vector<std::pair<size_t, size_t>> *ordering,
         // If set to size_t(-1), then print all copies of all objects.
         // Otherwise print a single copy of a single object.
         const size_t                     single_object_idx = size_t(-1));
@@ -258,6 +260,25 @@ protected:
         std::vector<Island>         islands;
     };
 
+	struct InstanceToPrint
+	{
+		InstanceToPrint(ObjectByExtruder &object_by_extruder, size_t layer_id, const PrintObject &print_object, size_t instance_id) :
+			object_by_extruder(object_by_extruder), layer_id(layer_id), print_object(print_object), instance_id(instance_id) {}
+
+		ObjectByExtruder	&object_by_extruder;
+		const size_t       		 layer_id;
+		const PrintObject 		&print_object;
+		// Instance idx of the copy of a print object.
+		const size_t			 instance_id;
+	};
+
+	std::vector<InstanceToPrint> sort_print_object_instances(
+		std::vector<ObjectByExtruder> 			&objects_by_extruder,
+		const std::vector<LayerToPrint> 				&layers,
+		// Ordering must be defined for normal (non-sequential print).
+		const std::vector<std::pair<size_t, size_t>> 	*ordering,
+		// For sequential print, the instance of the object to be printing has to be defined.
+		const size_t                     				 single_object_instance_idx);
 
     std::string     extrude_perimeters(const Print &print, const std::vector<ObjectByExtruder::Island::Region> &by_region, std::unique_ptr<EdgeGrid::Grid> &lower_layer_edge_grid);
     std::string     extrude_infill(const Print &print, const std::vector<ObjectByExtruder::Island::Region> &by_region);

src/libslic3r/Geometry.cpp

@@ -309,49 +309,7 @@ convex_hull(const Polygons &polygons)
     return convex_hull(std::move(pp));
 }
 
-/* accepts an arrayref of points and returns a list of indices
+bool directions_parallel(double angle1, double angle2, double max_diff)
-   according to a nearest-neighbor walk */
-void
-chained_path(const Points &points, std::vector<Points::size_type> &retval, Point start_near)
-{
-    PointConstPtrs my_points;
-    std::map<const Point*,Points::size_type> indices;
-    my_points.reserve(points.size());
-    for (Points::const_iterator it = points.begin(); it != points.end(); ++it) {
-        my_points.push_back(&*it);
-        indices[&*it] = it - points.begin();
-    }
-    
-    retval.reserve(points.size());
-    while (!my_points.empty()) {
-        Points::size_type idx = start_near.nearest_point_index(my_points);
-        start_near = *my_points[idx];
-        retval.push_back(indices[ my_points[idx] ]);
-        my_points.erase(my_points.begin() + idx);
-    }
-}
-
-void
-chained_path(const Points &points, std::vector<Points::size_type> &retval)
-{
-    if (points.empty()) return;  // can't call front() on empty vector
-    chained_path(points, retval, points.front());
-}
-
-/* retval and items must be different containers */
-template<class T>
-void
-chained_path_items(Points &points, T &items, T &retval)
-{
-    std::vector<Points::size_type> indices;
-    chained_path(points, indices);
-    for (std::vector<Points::size_type>::const_iterator it = indices.begin(); it != indices.end(); ++it)
-        retval.push_back(items[*it]);
-}
-template void chained_path_items(Points &points, ClipperLib::PolyNodes &items, ClipperLib::PolyNodes &retval);
-
-bool
-directions_parallel(double angle1, double angle2, double max_diff)
 {
     double diff = fabs(angle1 - angle2);
     max_diff += EPSILON;
@@ -359,8 +317,7 @@ directions_parallel(double angle1, double angle2, double max_diff)
 }
 
 template<class T>
-bool
+bool contains(const std::vector<T> &vector, const Point &point)
-contains(const std::vector<T> &vector, const Point &point)
 {
     for (typename std::vector<T>::const_iterator it = vector.begin(); it != vector.end(); ++it) {
         if (it->contains(point)) return true;
@@ -369,16 +326,14 @@ contains(const std::vector<T> &vector, const Point &point)
 }
 template bool contains(const ExPolygons &vector, const Point &point);
 
-double
+double rad2deg_dir(double angle)
-rad2deg_dir(double angle)
 {
     angle = (angle < PI) ? (-angle + PI/2.0) : (angle + PI/2.0);
     if (angle < 0) angle += PI;
     return rad2deg(angle);
 }
 
-void
+void simplify_polygons(const Polygons &polygons, double tolerance, Polygons* retval)
-simplify_polygons(const Polygons &polygons, double tolerance, Polygons* retval)
 {
     Polygons pp;
     for (Polygons::const_iterator it = polygons.begin(); it != polygons.end(); ++it) {
@@ -391,8 +346,7 @@ simplify_polygons(const Polygons &polygons, double tolerance, Polygons* retval)
     *retval = Slic3r::simplify_polygons(pp);
 }
 
-double
+double linint(double value, double oldmin, double oldmax, double newmin, double newmax)
-linint(double value, double oldmin, double oldmax, double newmin, double newmax)
 {
     return (value - oldmin) * (newmax - newmin) / (oldmax - oldmin) + newmin;
 }

src/libslic3r/Geometry.hpp

@@ -138,9 +138,6 @@ Pointf3s convex_hull(Pointf3s points);
 Polygon convex_hull(Points points);
 Polygon convex_hull(const Polygons &polygons);
 
-void chained_path(const Points &points, std::vector<Points::size_type> &retval, Point start_near);
-void chained_path(const Points &points, std::vector<Points::size_type> &retval);
-template<class T> void chained_path_items(Points &points, T &items, T &retval);
 bool directions_parallel(double angle1, double angle2, double max_diff = 0);
 template<class T> bool contains(const std::vector<T> &vector, const Point &point);
 template<typename T> T rad2deg(T angle) { return T(180.0) * angle / T(PI); }

src/libslic3r/KDTreeIndirect.hpp

@@ -0,0 +1,231 @@
+// KD tree built upon external data set, referencing the external data by integer indices.
+
+#ifndef slic3r_KDTreeIndirect_hpp_
+#define slic3r_KDTreeIndirect_hpp_
+
+#include <algorithm>
+#include <limits>
+#include <vector>
+
+#include "Utils.hpp" // for next_highest_power_of_2()
+
+namespace Slic3r {
+
+// KD tree for N-dimensional closest point search.
+template<size_t ANumDimensions, typename ACoordType, typename ACoordinateFn>
+class KDTreeIndirect
+{
+public:
+	static constexpr size_t NumDimensions = ANumDimensions;
+	using					CoordinateFn  = ACoordinateFn;
+	using					CoordType     = ACoordType;
+    // Following could be static constexpr size_t, but that would not link in C++11
+    enum : size_t {
+        npos = size_t(-1)
+    };
+
+	KDTreeIndirect(CoordinateFn coordinate) : coordinate(coordinate) {}
+	KDTreeIndirect(CoordinateFn coordinate, std::vector<size_t>   indices) : coordinate(coordinate) { this->build(std::move(indices)); }
+	KDTreeIndirect(CoordinateFn coordinate, std::vector<size_t> &&indices) : coordinate(coordinate) { this->build(std::move(indices)); }
+	KDTreeIndirect(CoordinateFn coordinate, size_t num_indices) : coordinate(coordinate) { this->build(num_indices); }
+	KDTreeIndirect(KDTreeIndirect &&rhs) : m_nodes(std::move(rhs.m_nodes)), coordinate(std::move(rhs.coordinate)) {}
+	KDTreeIndirect& operator=(KDTreeIndirect &&rhs) { m_nodes = std::move(rhs.m_nodes); coordinate = std::move(rhs.coordinate); return *this; }
+	void clear() { m_nodes.clear(); }
+
+	void build(size_t num_indices)
+	{
+		std::vector<size_t> indices;
+		indices.reserve(num_indices);
+		for (size_t i = 0; i < num_indices; ++ i)
+			indices.emplace_back(i);
+		this->build(std::move(indices));
+	}
+
+	void build(std::vector<size_t> &&indices)
+	{
+		if (indices.empty())
+			clear();
+		else {
+			// Allocate a next highest power of 2 nodes, because the incomplete binary tree will not have the leaves filled strictly from the left.
+			m_nodes.assign(next_highest_power_of_2(indices.size() + 1), npos);
+			build_recursive(indices, 0, 0, 0, (int)(indices.size() - 1));
+		}
+		indices.clear();
+	}
+
+	enum class VisitorReturnMask : unsigned int
+	{
+		CONTINUE_LEFT   = 1,
+		CONTINUE_RIGHT  = 2,
+		STOP 			= 4,
+	};
+	template<typename CoordType> 
+	unsigned int descent_mask(const CoordType &point_coord, const CoordType &search_radius, size_t idx, size_t dimension) const
+	{
+		CoordType dist = point_coord - this->coordinate(idx, dimension);
+		return (dist * dist < search_radius + CoordType(EPSILON)) ?
+			((unsigned int)(VisitorReturnMask::CONTINUE_LEFT) | (unsigned int)(VisitorReturnMask::CONTINUE_RIGHT)) :
+			(dist < CoordType(0)) ? (unsigned int)(VisitorReturnMask::CONTINUE_RIGHT) : (unsigned int)(VisitorReturnMask::CONTINUE_LEFT);
+	}
+
+	// Visitor is supposed to return a bit mask of VisitorReturnMask.
+	template<typename Visitor>
+	void visit(Visitor &visitor) const
+	{
+        visit_recursive(0, 0, visitor);
+	}
+
+	CoordinateFn coordinate;
+
+private:
+	// Build a balanced tree by splitting the input sequence by an axis aligned plane at a dimension.
+	void build_recursive(std::vector<size_t> &input, size_t node, int dimension, int left, int right)
+	{
+		if (left > right)
+			return;
+
+		assert(node < m_nodes.size());
+
+		if (left == right) {
+			// Insert a node into the balanced tree.
+			m_nodes[node] = input[left];
+			return;
+		}
+
+		// Partition the input sequence to two equal halves.
+		int center = (left + right) >> 1;
+		partition_input(input, dimension, left, right, center);
+		// Insert a node into the tree.
+		m_nodes[node] = input[center];
+		// Partition the left and right subtrees.
+		size_t next_dimension = (++ dimension == NumDimensions) ? 0 : dimension;
+		build_recursive(input, (node << 1) + 1, next_dimension, left,	    center - 1);
+		build_recursive(input, (node << 1) + 2, next_dimension, center + 1, right);
+	}
+
+	// Partition the input m_nodes <left, right> at k using QuickSelect method.
+	// https://en.wikipedia.org/wiki/Quickselect
+	void partition_input(std::vector<size_t> &input, int dimension, int left, int right, int k) const
+	{
+		while (left < right) {
+			// Guess the k'th element.
+			// Pick the pivot as a median of first, center and last value.
+			// Sort first, center and last values.
+			int  center       = (left + right) >> 1;
+			auto left_value   = this->coordinate(input[left],   dimension);
+			auto center_value = this->coordinate(input[center], dimension);
+			auto right_value  = this->coordinate(input[right],  dimension);
+			if (center_value < left_value) {
+				std::swap(input[left], input[center]);
+				std::swap(left_value,  center_value);
+			}
+			if (right_value < left_value) {
+				std::swap(input[left], input[right]);
+				std::swap(left_value,  right_value);
+			}
+			if (right_value < center_value) {
+				std::swap(input[center], input[right]);
+				// No need to do that, result is not used.
+				// std::swap(center_value,  right_value);
+			}
+			// Only two or three values are left and those are sorted already.
+			if (left + 3 > right)
+				break;
+			// left and right items are already at their correct positions.
+			// input[left].point[dimension] <= input[center].point[dimension] <= input[right].point[dimension]
+			// Move the pivot to the (right - 1) position.
+			std::swap(input[center], input[right - 1]);
+			// Pivot value.
+			double pivot = this->coordinate(input[right - 1],  dimension);
+			// Partition the set based on the pivot.
+			int i = left;
+			int j = right - 1;
+			for (;;) {
+				// Skip left points that are already at correct positions.
+				// Search will certainly stop at position (right - 1), which stores the pivot.
+				while (this->coordinate(input[++ i], dimension) < pivot) ;
+				// Skip right points that are already at correct positions.
+				while (this->coordinate(input[-- j], dimension) > pivot && i < j) ;
+				if (i >= j)
+					break;
+				std::swap(input[i], input[j]);
+			}
+			// Restore pivot to the center of the sequence.
+			std::swap(input[i], input[right]);
+			// Which side the kth element is in?
+			if (k < i)
+				right = i - 1;
+			else if (k == i)
+				// Sequence is partitioned, kth element is at its place.
+				break;
+			else
+				left = i + 1;
+		}
+	}
+
+	template<typename Visitor>
+	void visit_recursive(size_t node, size_t dimension, Visitor &visitor) const
+	{
+		assert(! m_nodes.empty());
+		if (node >= m_nodes.size() || m_nodes[node] == npos)
+			return;
+
+		// Left / right child node index.
+		size_t left  = (node << 1) + 1;
+		size_t right = left + 1;
+		unsigned int mask = visitor(m_nodes[node], dimension);
+		if ((mask & (unsigned int)VisitorReturnMask::STOP) == 0) {
+			size_t next_dimension = (++ dimension == NumDimensions) ? 0 : dimension;
+			if (mask & (unsigned int)VisitorReturnMask::CONTINUE_LEFT)
+				visit_recursive(left,  next_dimension, visitor);
+			if (mask & (unsigned int)VisitorReturnMask::CONTINUE_RIGHT)
+				visit_recursive(right, next_dimension, visitor);
+		}
+	}
+
+	std::vector<size_t> m_nodes;
+};
+
+// Find a closest point using Euclidian metrics.
+// Returns npos if not found.
+template<typename KDTreeIndirectType, typename PointType, typename FilterFn>
+size_t find_closest_point(const KDTreeIndirectType &kdtree, const PointType &point, FilterFn filter)
+{
+	struct Visitor {
+		using CoordType = typename KDTreeIndirectType::CoordType;
+		const KDTreeIndirectType   &kdtree;
+		const PointType    		   &point;
+		const FilterFn				filter;
+		size_t 						min_idx  = KDTreeIndirectType::npos;
+		CoordType					min_dist = std::numeric_limits<CoordType>::max();
+
+		Visitor(const KDTreeIndirectType &kdtree, const PointType &point, FilterFn filter) : kdtree(kdtree), point(point), filter(filter) {}
+		unsigned int operator()(size_t idx, size_t dimension) {
+			if (this->filter(idx)) {
+				auto dist = CoordType(0);
+				for (size_t i = 0; i < KDTreeIndirectType::NumDimensions; ++ i) {
+					CoordType d = point[i] - kdtree.coordinate(idx, i);
+					dist += d * d;
+				}
+				if (dist < min_dist) {
+					min_dist = dist;
+					min_idx  = idx;
+				}
+			}
+			return kdtree.descent_mask(point[dimension], min_dist, idx, dimension);
+		}
+	} visitor(kdtree, point, filter);
+
+	kdtree.visit(visitor);
+	return visitor.min_idx;
+}
+
+template<typename KDTreeIndirectType, typename PointType>
+size_t find_closest_point(const KDTreeIndirectType& kdtree, const PointType& point)
+{
+	return find_closest_point(kdtree, point, [](size_t) { return true; });
+}
+
+} // namespace Slic3r
+
+#endif /* slic3r_KDTreeIndirect_hpp_ */

src/libslic3r/Layer.cpp

@@ -1,8 +1,8 @@
 #include "Layer.hpp"
 #include "ClipperUtils.hpp"
-#include "Geometry.hpp"
 #include "Print.hpp"
 #include "Fill/Fill.hpp"
+#include "ShortestPath.hpp"
 #include "SVG.hpp"
 
 #include <boost/log/trivial.hpp>
@@ -57,8 +57,7 @@ void Layer::make_slices()
         ordering_points.push_back(ex.contour.first_point());
     
     // sort slices
-    std::vector<Points::size_type> order;
+    std::vector<Points::size_type> order = chain_points(ordering_points);
-    Slic3r::Geometry::chained_path(ordering_points, order);
     
     // populate slices vector
     for (size_t i : order)

src/libslic3r/Model.cpp

@@ -1462,7 +1462,7 @@ stl_stats ModelObject::get_object_stl_stats() const
         return this->volumes[0]->mesh().stl.stats;
 
     stl_stats full_stats;
-    memset(&full_stats, 0, sizeof(stl_stats));
+    full_stats.volume = 0.f;
 
     // fill full_stats from all objet's meshes
     for (ModelVolume* volume : this->volumes)

src/libslic3r/MutablePriorityQueue.hpp

@@ -13,21 +13,28 @@ public:
 		{}
 	~MutablePriorityQueue()	{ clear(); }
 
-	inline void		clear()								{ m_heap.clear(); }
+	void		clear();
-	inline void		reserve(size_t cnt) 				{ m_heap.reserve(cnt); }
+	void		reserve(size_t cnt) 				{ m_heap.reserve(cnt); }
-	inline void		push(const T &item);
+	void		push(const T &item);
-	inline void		push(T &&item);
+	void		push(T &&item);
-	inline void		pop();
+	void		pop();
-	inline T&		top()								{ return m_heap.front(); }
+	T&			top()								{ return m_heap.front(); }
-	inline void		remove(size_t idx);
+	void		remove(size_t idx);
-	inline void		update(size_t idx) 					{ T item = m_heap[idx]; remove(idx); push(item); }
+	void		update(size_t idx) 					{ T item = m_heap[idx]; remove(idx); push(item); }
 
-	inline size_t	size() const						{ return m_heap.size(); }
+	size_t		size() const						{ return m_heap.size(); }
-	inline bool		empty() const						{ return m_heap.empty(); }
+	bool		empty() const						{ return m_heap.empty(); }
+
+	using iterator		 = typename std::vector<T>::iterator;
+	using const_iterator = typename std::vector<T>::const_iterator;
+	iterator 		begin() 		{ return m_heap.begin(); }
+	iterator 		end() 			{ return m_heap.end(); }
+	const_iterator 	cbegin() const	{ return m_heap.cbegin(); }
+	const_iterator 	cend() const	{ return m_heap.cend(); }
 
 protected:
-	inline void		update_heap_up(size_t top, size_t bottom);
+	void		update_heap_up(size_t top, size_t bottom);
-	inline void		update_heap_down(size_t top, size_t bottom);
+	void		update_heap_down(size_t top, size_t bottom);
 
 private:
 	std::vector<T>	m_heap;
@@ -42,6 +49,17 @@ MutablePriorityQueue<T, IndexSetter, LessPredicate> make_mutable_priority_queue(
     	std::forward<IndexSetter>(index_setter), std::forward<LessPredicate>(less_predicate));
 }
 
+template<class T, class LessPredicate, class IndexSetter>
+inline void MutablePriorityQueue<T, LessPredicate, IndexSetter>::clear()
+{ 
+#ifndef NDEBUG
+	for (size_t idx = 0; idx < m_heap.size(); ++ idx)
+		// Mark as removed from the queue.
+		m_index_setter(m_heap[idx], std::numeric_limits<size_t>::max());
+#endif /* NDEBUG */
+	m_heap.clear();
+}
+
 template<class T, class LessPredicate, class IndexSetter>
 inline void MutablePriorityQueue<T, LessPredicate, IndexSetter>::push(const T &item)
 {
@@ -64,6 +82,10 @@ template<class T, class LessPredicate, class IndexSetter>
 inline void MutablePriorityQueue<T, LessPredicate, IndexSetter>::pop()
 {
 	assert(! m_heap.empty());
+#ifndef NDEBUG
+	// Mark as removed from the queue.
+	m_index_setter(m_heap.front(), std::numeric_limits<size_t>::max());
+#endif /* NDEBUG */
 	if (m_heap.size() > 1) {
 		m_heap.front() = m_heap.back();
 		m_heap.pop_back();
@@ -77,6 +99,10 @@ template<class T, class LessPredicate, class IndexSetter>
 inline void MutablePriorityQueue<T, LessPredicate, IndexSetter>::remove(size_t idx)
 {
 	assert(idx < m_heap.size());
+#ifndef NDEBUG
+	// Mark as removed from the queue.
+	m_index_setter(m_heap[idx], std::numeric_limits<size_t>::max());
+#endif /* NDEBUG */
 	if (idx + 1 == m_heap.size()) {
 		m_heap.pop_back();
 		return;

src/libslic3r/PerimeterGenerator.cpp

@@ -1,6 +1,8 @@
 #include "PerimeterGenerator.hpp"
 #include "ClipperUtils.hpp"
 #include "ExtrusionEntityCollection.hpp"
+#include "ShortestPath.hpp"
+
 #include <cmath>
 #include <cassert>
 
@@ -86,24 +88,24 @@ static ExtrusionPaths thick_polyline_to_extrusion_paths(const ThickPolyline &thi
     return paths;
 }
 
-static ExtrusionEntityCollection variable_width(const ThickPolylines& polylines, ExtrusionRole role, Flow flow)
+static void variable_width(const ThickPolylines& polylines, ExtrusionRole role, Flow flow, std::vector<ExtrusionEntity*> &out)
 {
 	// This value determines granularity of adaptive width, as G-code does not allow
 	// variable extrusion within a single move; this value shall only affect the amount
 	// of segments, and any pruning shall be performed before we apply this tolerance.
-	ExtrusionEntityCollection coll;
 	const float tolerance = float(scale_(0.05));
 	for (const ThickPolyline &p : polylines) {
 		ExtrusionPaths paths = thick_polyline_to_extrusion_paths(p, role, flow, tolerance);
 		// Append paths to collection.
 		if (! paths.empty()) {
 			if (paths.front().first_point() == paths.back().last_point())
-				coll.append(ExtrusionLoop(std::move(paths)));
+				out.emplace_back(new ExtrusionLoop(std::move(paths)));
-			else
+			else {
-				coll.append(std::move(paths));
+				for (ExtrusionPath &path : paths)
+					out.emplace_back(new ExtrusionPath(std::move(path)));
+			}
 		}
 	}
-	return coll;
 }
 
 // Hierarchy of perimeters.
@@ -186,43 +188,47 @@ static ExtrusionEntityCollection traverse_loops(const PerimeterGenerator &perime
             paths.push_back(path);
         }
         
-        coll.append(ExtrusionLoop(paths, loop_role));
+        coll.append(ExtrusionLoop(std::move(paths), loop_role));
     }
     
     // Append thin walls to the nearest-neighbor search (only for first iteration)
     if (! thin_walls.empty()) {
-        ExtrusionEntityCollection tw = variable_width(thin_walls, erExternalPerimeter, perimeter_generator.ext_perimeter_flow);
+        variable_width(thin_walls, erExternalPerimeter, perimeter_generator.ext_perimeter_flow, coll.entities);
-        coll.append(tw.entities);
         thin_walls.clear();
     }
     
-    // Sort entities into a new collection using a nearest-neighbor search,
+    // Traverse children and build the final collection.
-    // preserving the original indices which are useful for detecting thin walls.
+	Point zero_point(0, 0);
-    ExtrusionEntityCollection sorted_coll;
+	std::vector<std::pair<size_t, bool>> chain = chain_extrusion_entities(coll.entities, &zero_point);
-    coll.chained_path(&sorted_coll, false, erMixed, &sorted_coll.orig_indices);
+    ExtrusionEntityCollection out;
-    
+    for (const std::pair<size_t, bool> &idx : chain) {
-    // traverse children and build the final collection
+		assert(coll.entities[idx.first] != nullptr);
-    ExtrusionEntityCollection entities;
+        if (idx.first >= loops.size()) {
-    for (const size_t &idx : sorted_coll.orig_indices) {
+            // This is a thin wall.
-        if (idx >= loops.size()) {
+			out.entities.reserve(out.entities.size() + 1);
-            // This is a thin wall. Let's get it from the sorted collection as it might have been reversed.
+            out.entities.emplace_back(coll.entities[idx.first]);
-            entities.append(std::move(*sorted_coll.entities[&idx - &sorted_coll.orig_indices.front()]));
+			coll.entities[idx.first] = nullptr;
+            if (idx.second)
+				out.entities.back()->reverse();
         } else {
-            const PerimeterGeneratorLoop &loop = loops[idx];
+            const PerimeterGeneratorLoop &loop = loops[idx.first];
-            ExtrusionLoop eloop = *dynamic_cast<ExtrusionLoop*>(coll.entities[idx]);
+            assert(thin_walls.empty());
             ExtrusionEntityCollection children = traverse_loops(perimeter_generator, loop.children, thin_walls);
+            out.entities.reserve(out.entities.size() + children.entities.size() + 1);
+            ExtrusionLoop *eloop = static_cast<ExtrusionLoop*>(coll.entities[idx.first]);
+            coll.entities[idx.first] = nullptr;
             if (loop.is_contour) {
-                eloop.make_counter_clockwise();
+                eloop->make_counter_clockwise();
-                entities.append(std::move(children.entities));
+                out.append(std::move(children.entities));
-                entities.append(std::move(eloop));
+                out.entities.emplace_back(eloop);
             } else {
-                eloop.make_clockwise();
+                eloop->make_clockwise();
-                entities.append(std::move(eloop));
+                out.entities.emplace_back(eloop);
-                entities.append(std::move(children.entities));
+                out.append(std::move(children.entities));
             }
         }
     }
-    return entities;
+    return out;
 }
 
 void PerimeterGenerator::process()
@@ -445,8 +451,8 @@ void PerimeterGenerator::process()
             for (const ExPolygon &ex : gaps_ex)
                 ex.medial_axis(max, min, &polylines);
             if (! polylines.empty()) {
-                ExtrusionEntityCollection gap_fill = variable_width(polylines, erGapFill, this->solid_infill_flow);
+				ExtrusionEntityCollection gap_fill;
-                this->gap_fill->append(gap_fill.entities);
+				variable_width(polylines, erGapFill, this->solid_infill_flow, gap_fill.entities);
                 /*  Make sure we don't infill narrow parts that are already gap-filled
                     (we only consider this surface's gaps to reduce the diff() complexity).
                     Growing actual extrusions ensures that gaps not filled by medial axis
@@ -456,6 +462,7 @@ void PerimeterGenerator::process()
                 //FIXME Vojtech: This grows by a rounded extrusion width, not by line spacing,
                 // therefore it may cover the area, but no the volume.
                 last = diff_ex(to_polygons(last), gap_fill.polygons_covered_by_width(10.f));
+				this->gap_fill->append(std::move(gap_fill.entities));
 			}
         }
 

src/libslic3r/Polyline.cpp

@@ -23,12 +23,6 @@ Polyline::operator Line() const
     return Line(this->points.front(), this->points.back());
 }
 
-Point
-Polyline::last_point() const
-{
-    return this->points.back();
-}
-
 Point
 Polyline::leftmost_point() const
 {

src/libslic3r/Polyline.hpp

@@ -62,7 +62,8 @@ public:
 
     operator Polylines() const;
     operator Line() const;
-    Point last_point() const;
+    Point    last_point() const override { return this->points.back(); }
+
     Point leftmost_point() const;
     virtual Lines lines() const;
     void clip_end(double distance);

src/libslic3r/Print.cpp

@@ -7,6 +7,7 @@
 #include "Flow.hpp"
 #include "Geometry.hpp"
 #include "I18N.hpp"
+#include "ShortestPath.hpp"
 #include "SupportMaterial.hpp"
 #include "GCode.hpp"
 #include "GCode/WipeTower.hpp"
@@ -1824,8 +1825,8 @@ void Print::_make_brim()
 				[](const std::pair<const ClipperLib_Z::Path*, size_t> &l, const std::pair<const ClipperLib_Z::Path*, size_t> &r) {
 					return l.second < r.second;
 				});
-			Vec3f last_pt(0.f, 0.f, 0.f);
 
+			Point last_pt(0, 0);
 			for (size_t i = 0; i < loops_trimmed_order.size();) {
 				// Find all pieces that the initial loop was split into.
 				size_t j = i + 1;
@@ -1841,16 +1842,23 @@ void Print::_make_brim()
 		            	points.emplace_back(coord_t(pt.X), coord_t(pt.Y));
 		            i = j;
 				} else {
-			    	//FIXME this is not optimal as the G-code generator will follow the sequence of paths verbatim without respect to minimum travel distance.
+			    	//FIXME The path chaining here may not be optimal.
+			    	ExtrusionEntityCollection this_loop_trimmed;
+					this_loop_trimmed.entities.reserve(j - i);
 			    	for (; i < j; ++ i) {
-			            m_brim.entities.emplace_back(new ExtrusionPath(erSkirt, float(flow.mm3_per_mm()), float(flow.width), float(this->skirt_first_layer_height())));
+			            this_loop_trimmed.entities.emplace_back(new ExtrusionPath(erSkirt, float(flow.mm3_per_mm()), float(flow.width), float(this->skirt_first_layer_height())));
 						const ClipperLib_Z::Path &path = *loops_trimmed_order[i].first;
-			            Points &points = static_cast<ExtrusionPath*>(m_brim.entities.back())->polyline.points;
+			            Points &points = static_cast<ExtrusionPath*>(this_loop_trimmed.entities.back())->polyline.points;
 			            points.reserve(path.size());
 			            for (const ClipperLib_Z::IntPoint &pt : path)
 			            	points.emplace_back(coord_t(pt.X), coord_t(pt.Y));
 		           	}
+		           	chain_and_reorder_extrusion_entities(this_loop_trimmed.entities, &last_pt);
+		           	m_brim.entities.reserve(m_brim.entities.size() + this_loop_trimmed.entities.size());
+		           	append(m_brim.entities, std::move(this_loop_trimmed.entities));
+		           	this_loop_trimmed.entities.clear();
 		        }
+		        last_pt = m_brim.last_point();
 			}
 		}
     } else {

src/libslic3r/Print.hpp

@@ -96,6 +96,7 @@ public:
     const SupportLayerPtrs& support_layers() const  { return m_support_layers; }
     const Transform3d&      trafo() const           { return m_trafo; }
     const Points&           copies() const          { return m_copies; }
+    const Point 			copy_center(size_t idx) const { return m_copies[idx] + m_copies_shift + Point(this->size.x() / 2, this->size.y() / 2); }
 
     // since the object is aligned to origin, bounding box coincides with size
     BoundingBox bounding_box() const { return BoundingBox(Point(0,0), to_2d(this->size)); }

src/libslic3r/PrintBase.hpp

@@ -268,8 +268,7 @@ public:
         std::string     text;
         // Bitmap of flags.
         enum FlagBits {
-            DEFAULT,
+            DEFAULT                         = 0,
-            NO_RELOAD_SCENE                 = 0,
             RELOAD_SCENE                    = 1 << 1,
             RELOAD_SLA_SUPPORT_POINTS       = 1 << 2,
             RELOAD_SLA_PREVIEW              = 1 << 3,

src/libslic3r/PrintObject.cpp

@@ -12,7 +12,6 @@
 #include <boost/log/trivial.hpp>
 #include <float.h>
 
-#include <tbb/task_scheduler_init.h>
 #include <tbb/parallel_for.h>
 #include <tbb/atomic.h>
 
@@ -75,13 +74,9 @@ PrintBase::ApplyStatus PrintObject::set_copies(const Points &points)
 {
     // Order copies with a nearest-neighbor search.
     std::vector<Point> copies;
-    {
+    copies.reserve(points.size());
-        std::vector<Points::size_type> ordered_copies;
+    for (const Point &pt : points)
-        Slic3r::Geometry::chained_path(points, ordered_copies);
+        copies.emplace_back(pt + m_copies_shift);
-        copies.reserve(ordered_copies.size());
-        for (size_t point_idx : ordered_copies)
-            copies.emplace_back(points[point_idx] + m_copies_shift);
-    }
     // Invalidate and set copies.
     PrintBase::ApplyStatus status = PrintBase::APPLY_STATUS_UNCHANGED;
     if (copies != m_copies) {

src/libslic3r/ShortestPath.cpp

@@ -0,0 +1,394 @@
+#if 0
+	#pragma optimize("", off)
+	#undef NDEBUG
+	#undef assert
+#endif
+
+#include "clipper.hpp"
+#include "ShortestPath.hpp"
+#include "KDTreeIndirect.hpp"
+#include "MutablePriorityQueue.hpp"
+#include "Print.hpp"
+
+#include <cmath>
+#include <cassert>
+
+namespace Slic3r {
+
+// Chain perimeters (always closed) and thin fills (closed or open) using a greedy algorithm.
+// Solving a Traveling Salesman Problem (TSP) with the modification, that the sites are not always points, but points and segments.
+// Solving using a greedy algorithm, where a shortest edge is added to the solution if it does not produce a bifurcation or a cycle.
+// Return index and "reversed" flag.
+// https://en.wikipedia.org/wiki/Multi-fragment_algorithm
+// The algorithm builds a tour for the traveling salesman one edge at a time and thus maintains multiple tour fragments, each of which 
+// is a simple path in the complete graph of cities. At each stage, the algorithm selects the edge of minimal cost that either creates 
+// a new fragment, extends one of the existing paths or creates a cycle of length equal to the number of cities.
+template<typename PointType, typename SegmentEndPointFunc>
+std::vector<std::pair<size_t, bool>> chain_segments(SegmentEndPointFunc end_point_func, size_t num_segments, const PointType *start_near)
+{
+	std::vector<std::pair<size_t, bool>> out;
+
+	if (num_segments == 0) {
+		// Nothing to do.
+	} 
+	else if (num_segments == 1)
+	{
+		// Just sort the end points so that the first point visited is closest to start_near.
+		out.emplace_back(0, start_near != nullptr && 
+            (end_point_func(0, true) - *start_near).template cast<double>().squaredNorm() < (end_point_func(0, false) - *start_near).template cast<double>().squaredNorm());
+	} 
+	else
+	{
+		// End points of segments for the KD tree closest point search.
+		// A single end point is inserted into the search structure for loops, two end points are entered for open paths.
+		struct EndPoint {
+			EndPoint(const Vec2d &pos) : pos(pos) {}
+			Vec2d     pos;
+			// Identifier of the chain, to which this end point belongs. Zero means unassigned.
+			size_t    chain_id = 0;
+			// Link to the closest currently valid end point.
+			EndPoint *edge_out = nullptr;
+			// Distance to the next end point following the link.
+			// Zero value -> start of the final path.
+			double    distance_out = std::numeric_limits<double>::max();
+			size_t    heap_idx = std::numeric_limits<size_t>::max();
+		};
+	    std::vector<EndPoint> end_points;
+	    end_points.reserve(num_segments * 2);
+	    for (size_t i = 0; i < num_segments; ++ i) {
+            end_points.emplace_back(end_point_func(i, true ).template cast<double>());
+            end_points.emplace_back(end_point_func(i, false).template cast<double>());
+	    }
+
+	    // Construct the closest point KD tree over end points of segments.
+		auto coordinate_fn = [&end_points](size_t idx, size_t dimension) -> double { return end_points[idx].pos[dimension]; };
+		KDTreeIndirect<2, double, decltype(coordinate_fn)> kdtree(coordinate_fn, end_points.size());
+
+		// Helper to detect loops in already connected paths.
+		// Unique chain IDs are assigned to paths. If paths are connected, end points will not have their chain IDs updated, but the chain IDs
+		// will remember an "equivalent" chain ID, which is the lowest ID of all the IDs in the path, and the lowest ID is equivalent to itself.
+		class EquivalentChains {
+		public:
+			// Zero'th chain ID is invalid.
+			EquivalentChains(size_t reserve) { m_equivalent_with.reserve(reserve); m_equivalent_with.emplace_back(0); }
+			// Generate next equivalence class.
+			size_t 				next() {
+				m_equivalent_with.emplace_back(++ m_last_chain_id);
+				return m_last_chain_id;
+			}
+			// Get equivalence class for chain ID.
+			size_t 				operator()(size_t chain_id) {
+				if (chain_id != 0) {
+					for (size_t last = chain_id;;) {
+						size_t lower = m_equivalent_with[last];
+						if (lower == last) {
+							m_equivalent_with[chain_id] = lower;
+							chain_id = lower;
+							break;
+						}
+						last = lower;
+					}
+				}
+				return chain_id;
+			}
+			size_t 			  	merge(size_t chain_id1, size_t chain_id2) {
+				size_t chain_id = std::min((*this)(chain_id1), (*this)(chain_id2));
+				m_equivalent_with[chain_id1] = chain_id;
+				m_equivalent_with[chain_id2] = chain_id;
+				return chain_id;
+			}
+
+#ifndef NDEBUG
+			bool				validate()
+			{
+				assert(m_last_chain_id >= 0);
+				assert(m_last_chain_id + 1 == m_equivalent_with.size());
+				for (size_t i = 0; i < m_equivalent_with.size(); ++ i) {
+					for (size_t last = i;;) {
+						size_t lower = m_equivalent_with[last];
+						assert(lower <= last);
+						if (lower == last)
+							break;
+						last = lower;
+					}
+				}
+				return true;
+			}
+#endif /* NDEBUG */
+
+		private:
+			// Unique chain ID assigned to chains of end points of segments.
+			size_t              m_last_chain_id = 0;
+			std::vector<size_t> m_equivalent_with;
+		} equivalent_chain(num_segments);
+
+		// Find the first end point closest to start_near.
+		EndPoint *first_point = nullptr;
+		size_t    first_point_idx = std::numeric_limits<size_t>::max();
+		if (start_near != nullptr) {
+            size_t idx = find_closest_point(kdtree, start_near->template cast<double>());
+			assert(idx < end_points.size());
+			first_point = &end_points[idx];
+			first_point->distance_out = 0.;
+			first_point->chain_id = equivalent_chain.next();
+			first_point_idx = idx;
+		}
+
+		// Assign the closest point and distance to the end points.
+		for (EndPoint &end_point : end_points) {
+	    	assert(end_point.edge_out == nullptr);
+	    	if (&end_point != first_point) {
+		    	size_t this_idx = &end_point - &end_points.front();
+		    	// Find the closest point to this end_point, which lies on a different extrusion path (filtered by the lambda).
+		    	// Ignore the starting point as the starting point is considered to be occupied, no end point coud connect to it.
+				size_t next_idx = find_closest_point(kdtree, end_point.pos, 
+					[this_idx, first_point_idx](size_t idx){ return idx != first_point_idx && (idx ^ this_idx) > 1; });
+				assert(next_idx < end_points.size());
+				EndPoint &end_point2 = end_points[next_idx];
+				end_point.edge_out = &end_point2;
+				end_point.distance_out = (end_point2.pos - end_point.pos).squaredNorm();
+			}
+		}
+
+	    // Initialize a heap of end points sorted by the lowest distance to the next valid point of a path.
+	    auto queue = make_mutable_priority_queue<EndPoint*>(
+			[](EndPoint *ep, size_t idx){ ep->heap_idx = idx; }, 
+	    	[](EndPoint *l, EndPoint *r){ return l->distance_out < r->distance_out; });
+		queue.reserve(end_points.size() * 2 - 1);
+	    for (EndPoint &ep : end_points)
+	    	if (first_point != &ep)
+				queue.push(&ep);
+
+#ifndef NDEBUG
+		auto validate_graph_and_queue = [&equivalent_chain, &end_points, &queue, first_point]() -> bool {
+			assert(equivalent_chain.validate());
+			for (EndPoint &ep : end_points) {
+				if (ep.heap_idx < queue.size()) {
+					// End point is on the heap.
+					assert(*(queue.cbegin() + ep.heap_idx) == &ep);
+					assert(ep.chain_id == 0);
+				} else {
+					// End point is NOT on the heap, therefore it is part of the output path.
+					assert(ep.heap_idx == std::numeric_limits<size_t>::max());
+					assert(ep.chain_id != 0);
+					if (&ep == first_point) {
+						assert(ep.edge_out == nullptr);
+					} else {
+						assert(ep.edge_out != nullptr);
+						// Detect loops.
+						for (EndPoint *pt = &ep; pt != nullptr;) {
+							// Out of queue. It is a final point.
+							assert(pt->heap_idx == std::numeric_limits<size_t>::max());
+							EndPoint *pt_other = &end_points[(pt - &end_points.front()) ^ 1];
+							if (pt_other->heap_idx < queue.size())
+								// The other side of this segment is undecided yet.
+								break;
+							pt = pt_other->edge_out;
+						}
+					}
+				}
+			}
+			for (EndPoint *ep : queue)
+				// Points in the queue are not connected yet.
+				assert(ep->chain_id == 0);
+			return true;
+		};
+#endif /* NDEBUG */
+
+	    // Chain the end points: find (num_segments - 1) shortest links not forming bifurcations or loops.
+		assert(num_segments >= 2);
+		for (int iter = int(num_segments) - 2;; -- iter) {
+			assert(validate_graph_and_queue());
+	    	// Take the first end point, for which the link points to the currently closest valid neighbor.
+	    	EndPoint &end_point1 = *queue.top();
+	    	assert(end_point1.edge_out != nullptr);
+	    	// No point on the queue may be connected yet.
+	    	assert(end_point1.chain_id == 0);
+	    	// Take the closest end point to the first end point,
+	    	EndPoint &end_point2 = *end_point1.edge_out;
+	    	bool valid = true;
+	    	size_t end_point1_other_chain_id = 0;
+	    	size_t end_point2_other_chain_id = 0;
+	    	if (end_point2.chain_id > 0) {
+	    		// The other side is part of the output path. Don't connect to end_point2, update end_point1 and try another one.
+	    		valid = false;
+	    	} else {
+				// End points of the opposite ends of the segments.
+				end_point1_other_chain_id = equivalent_chain(end_points[(&end_point1 - &end_points.front()) ^ 1].chain_id);
+				end_point2_other_chain_id = equivalent_chain(end_points[(&end_point2 - &end_points.front()) ^ 1].chain_id);
+				if (end_point1_other_chain_id == end_point2_other_chain_id && end_point1_other_chain_id != 0)
+					// This edge forms a loop. Update end_point1 and try another one.
+					valid = false;
+	    	}
+	    	if (valid) {
+		    	// Remove the first and second point from the queue.
+				queue.pop();
+		    	queue.remove(end_point2.heap_idx);
+		    	assert(end_point1.edge_out = &end_point2);
+		    	end_point2.edge_out = &end_point1;
+		    	end_point2.distance_out = end_point1.distance_out;
+		    	// Assign chain IDs to the newly connected end points, set equivalent_chain if two chains were merged.
+		    	size_t chain_id =
+					(end_point1_other_chain_id == 0) ?
+						((end_point2_other_chain_id == 0) ? equivalent_chain.next() : end_point2_other_chain_id) :
+						((end_point2_other_chain_id == 0) ? end_point1_other_chain_id : 
+							(end_point1_other_chain_id == end_point2_other_chain_id) ? 
+								end_point1_other_chain_id :
+								equivalent_chain.merge(end_point1_other_chain_id, end_point2_other_chain_id));
+				end_point1.chain_id = chain_id;
+				end_point2.chain_id = chain_id;
+				assert(validate_graph_and_queue());
+				if (iter == 0) {
+					// Last iteration. There shall be exactly one or two end points waiting to be connected.
+					assert(queue.size() == ((first_point == nullptr) ? 2 : 1));
+					if (first_point == nullptr)
+						first_point = queue.top();
+					while (! queue.empty()) {
+						queue.top()->edge_out = nullptr;
+						queue.pop();
+					}
+					break;
+				}
+	    	} else {
+				// This edge forms a loop. Update end_point1 and try another one.
+				++ iter;
+				end_point1.edge_out = nullptr;
+		    	// Update edge_out and distance.
+		    	size_t this_idx = &end_point1 - &end_points.front();
+		    	// Find the closest point to this end_point, which lies on a different extrusion path (filtered by the filter lambda).
+				size_t next_idx = find_closest_point(kdtree, end_point1.pos, [&end_points, &equivalent_chain, this_idx](size_t idx) { 
+			    	assert(end_points[this_idx].edge_out == nullptr);
+			    	assert(end_points[this_idx].chain_id == 0);
+					if ((idx ^ this_idx) <= 1 || end_points[idx].chain_id != 0)
+						// Points of the same segment shall not be connected,
+						// cannot connect to an already connected point (ideally those would be removed from the KD tree, but the update is difficult).
+						return false;
+			    	size_t chain1 = equivalent_chain(end_points[this_idx ^ 1].chain_id);
+			    	size_t chain2 = equivalent_chain(end_points[idx      ^ 1].chain_id);
+			    	return chain1 != chain2 || chain1 == 0;
+				});
+				assert(next_idx < end_points.size());
+				end_point1.edge_out = &end_points[next_idx];
+				end_point1.distance_out = (end_points[next_idx].pos - end_point1.pos).squaredNorm();
+				// Update position of this end point in the queue based on the distance calculated at the line above.
+				queue.update(end_point1.heap_idx);
+		    	//FIXME Remove the other end point from the KD tree.
+		    	// As the KD tree update is expensive, do it only after some larger number of points is removed from the queue.
+				assert(validate_graph_and_queue());
+	    	}
+		}
+		assert(queue.empty());
+
+		// Now interconnect pairs of segments into a chain.
+		assert(first_point != nullptr);
+		do {
+			assert(out.size() < num_segments);
+			size_t    		 first_point_id = first_point - &end_points.front();
+			size_t           segment_id 	= first_point_id >> 1;
+			EndPoint 		*second_point   = &end_points[first_point_id ^ 1];
+			out.emplace_back(segment_id, (first_point_id & 1) != 0);
+			first_point = second_point->edge_out;
+		} while (first_point != nullptr);
+	}
+
+	assert(out.size() == num_segments);
+	return out;
+}
+
+std::vector<std::pair<size_t, bool>> chain_extrusion_entities(std::vector<ExtrusionEntity*> &entities, const Point *start_near)
+{
+	auto segment_end_point = [&entities](size_t idx, bool first_point) -> const Point& { return first_point ? entities[idx]->first_point() : entities[idx]->last_point(); };
+	std::vector<std::pair<size_t, bool>> out = chain_segments<Point, decltype(segment_end_point)>(segment_end_point, entities.size(), start_near);
+	for (size_t i = 0; i < entities.size(); ++ i) {
+		ExtrusionEntity *ee = entities[i];
+		if (ee->is_loop())
+			// Ignore reversals for loops, as the start point equals the end point.
+			out[i].second = false;
+		// Is can_reverse() respected by the reversals?
+		assert(entities[i]->can_reverse() || ! out[i].second);
+	}
+	return out;
+}
+
+void reorder_extrusion_entities(std::vector<ExtrusionEntity*> &entities, const std::vector<std::pair<size_t, bool>> &chain)
+{
+	assert(entities.size() == chain.size());
+	std::vector<ExtrusionEntity*> out;
+	out.reserve(entities.size());
+    for (const std::pair<size_t, bool> &idx : chain) {
+		assert(entities[idx.first] != nullptr);
+        out.emplace_back(entities[idx.first]);
+        if (idx.second)
+			out.back()->reverse();
+    }
+    entities.swap(out);
+}
+
+void chain_and_reorder_extrusion_entities(std::vector<ExtrusionEntity*> &entities, const Point *start_near)
+{
+	reorder_extrusion_entities(entities, chain_extrusion_entities(entities, start_near));
+}
+
+std::vector<size_t> chain_points(const Points &points, Point *start_near)
+{
+	auto segment_end_point = [&points](size_t idx, bool /* first_point */) -> const Point& { return points[idx]; };
+	std::vector<std::pair<size_t, bool>> ordered = chain_segments<Point, decltype(segment_end_point)>(segment_end_point, points.size(), start_near);
+	std::vector<size_t> out;
+	out.reserve(ordered.size());
+	for (auto &segment_and_reversal : ordered)
+		out.emplace_back(segment_and_reversal.first);
+	return out;
+}
+
+Polylines chain_infill_polylines(Polylines &&polylines)
+{
+	auto segment_end_point = [&polylines](size_t idx, bool first_point) -> const Point& { return first_point ? polylines[idx].first_point() : polylines[idx].last_point(); };
+	std::vector<std::pair<size_t, bool>> ordered = chain_segments<Point, decltype(segment_end_point)>(segment_end_point, polylines.size(), nullptr);
+	Polylines out;
+	out.reserve(polylines.size());
+	for (auto &segment_and_reversal : ordered) {
+		out.emplace_back(std::move(polylines[segment_and_reversal.first]));
+		if (segment_and_reversal.second)
+			out.back().reverse();
+	}
+	return out;	
+}
+
+template<class T> static inline T chain_path_items(const Points &points, const T &items)
+{
+	auto segment_end_point = [&points](size_t idx, bool /* first_point */) -> const Point& { return points[idx]; };
+	std::vector<std::pair<size_t, bool>> ordered = chain_segments<Point, decltype(segment_end_point)>(segment_end_point, points.size(), nullptr);
+	T out;
+	out.reserve(items.size());
+	for (auto &segment_and_reversal : ordered)
+		out.emplace_back(items[segment_and_reversal.first]);
+	return out;
+}
+
+ClipperLib::PolyNodes chain_clipper_polynodes(const Points &points, const ClipperLib::PolyNodes &items)
+{
+	return chain_path_items(points, items);
+}
+
+std::vector<std::pair<size_t, size_t>> chain_print_object_instances(const Print &print)
+{
+    // Order objects using a nearest neighbor search.
+    Points object_reference_points;
+    std::vector<std::pair<size_t, size_t>> instances;
+    for (size_t i = 0; i < print.objects().size(); ++ i) {
+    	const PrintObject &object = *print.objects()[i];
+    	for (size_t j = 0; j < object.copies().size(); ++ j) {
+        	object_reference_points.emplace_back(object.copy_center(j));
+        	instances.emplace_back(i, j);
+        }
+    }
+	auto segment_end_point = [&object_reference_points](size_t idx, bool /* first_point */) -> const Point& { return object_reference_points[idx]; };
+	std::vector<std::pair<size_t, bool>> ordered = chain_segments<Point, decltype(segment_end_point)>(segment_end_point, instances.size(), nullptr);
+    std::vector<std::pair<size_t, size_t>> out;
+	out.reserve(instances.size());
+	for (auto &segment_and_reversal : ordered)
+		out.emplace_back(instances[segment_and_reversal.first]);
+	return out;
+}
+
+} // namespace Slic3r

src/libslic3r/ShortestPath.hpp

@@ -0,0 +1,33 @@
+#ifndef slic3r_ShortestPath_hpp_
+#define slic3r_ShortestPath_hpp_
+
+#include "libslic3r.h"
+#include "ExtrusionEntity.hpp"
+#include "Point.hpp"
+
+#include <utility>
+#include <vector>
+
+namespace ClipperLib { class PolyNode; }
+
+namespace Slic3r {
+
+std::vector<size_t> 				 chain_points(const Points &points, Point *start_near = nullptr);
+
+std::vector<std::pair<size_t, bool>> chain_extrusion_entities(std::vector<ExtrusionEntity*> &entities, const Point *start_near = nullptr);
+void                                 reorder_extrusion_entities(std::vector<ExtrusionEntity*> &entities, const std::vector<std::pair<size_t, bool>> &chain);
+void                                 chain_and_reorder_extrusion_entities(std::vector<ExtrusionEntity*> &entities, const Point *start_near = nullptr);
+
+Polylines 							 chain_infill_polylines(Polylines &&src);
+
+std::vector<ClipperLib::PolyNode*>	 chain_clipper_polynodes(const Points &points, const std::vector<ClipperLib::PolyNode*> &items);
+
+// Chain instances of print objects by an approximate shortest path.
+// Returns pairs of PrintObject idx and instance of that PrintObject.
+class Print;
+std::vector<std::pair<size_t, size_t>> chain_print_object_instances(const Print &print);
+
+
+} // namespace Slic3r
+
+#endif /* slic3r_ShortestPath_hpp_ */

src/libslic3r/SupportMaterial.cpp

@@ -2125,7 +2125,7 @@ void PrintObjectSupportMaterial::trim_support_layers_by_object(
                 }
                 // $layer->slices contains the full shape of layer, thus including
                 // perimeter's width. $support contains the full shape of support
-                // material, thus including the width of its foremost extrusion.
+                // material, thus including the width of its foremost extrusion.
                 // We leave a gap equal to a full extrusion width.
                 support_layer.polygons = diff(support_layer.polygons, polygons_trimming);
             }
@@ -2934,20 +2934,13 @@ void PrintObjectSupportMaterial::generate_toolpaths(
     // Prepare fillers.
     SupportMaterialPattern  support_pattern = m_object_config->support_material_pattern;
     bool                    with_sheath     = m_object_config->support_material_with_sheath;
-    InfillPattern           infill_pattern;
+    InfillPattern           infill_pattern = (support_pattern == smpHoneycomb ? ipHoneycomb : ipRectilinear);
     std::vector<float>      angles;
     angles.push_back(base_angle);
-    switch (support_pattern) {
+
-    case smpRectilinearGrid:
+    if (support_pattern == smpRectilinearGrid)
         angles.push_back(interface_angle);
-        // fall through
+
-    case smpRectilinear:
-        infill_pattern = ipRectilinear;
-        break;
-    case smpHoneycomb:
-        infill_pattern = ipHoneycomb;
-        break;
-    }
     BoundingBox bbox_object(Point(-scale_(1.), -scale_(1.0)), Point(scale_(1.), scale_(1.)));
 
 //    const coordf_t link_max_length_factor = 3.;
@@ -3217,7 +3210,7 @@ void PrintObjectSupportMaterial::generate_toolpaths(
                     density = 0.5f;
                     flow = m_first_layer_flow;
                     // use the proper spacing for first layer as we don't need to align
-                    // its pattern to the other layers
+                    // its pattern to the other layers
                     //FIXME When paralellizing, each thread shall have its own copy of the fillers.
                     filler->spacing = flow.spacing();
                     filler->link_max_length = coord_t(scale_(filler->spacing * link_max_length_factor / density));

src/slic3r/GUI/GLCanvas3D.cpp

@@ -3413,11 +3413,10 @@ void GLCanvas3D::handle_sidebar_focus_event(const std::string& opt_key, bool foc
     m_sidebar_field = focus_on ? opt_key : "";
 
     if (!m_sidebar_field.empty())
-    {
         m_gizmos.reset_all_states();
+
     m_dirty = true;
 }
-}
 
 void GLCanvas3D::handle_layers_data_focus_event(const t_layer_height_range range, const EditorType type)
 {

src/slic3r/GUI/GUI_ObjectList.cpp

@@ -753,9 +753,9 @@ void ObjectList::paste_volumes_into_list(int obj_idx, const ModelVolumePtrs& vol
     }
 
     select_items(items);
-#ifndef __WXOSX__ //#ifdef __WXMSW__ // #ys_FIXME
+//#ifndef __WXOSX__ //#ifdef __WXMSW__ // #ys_FIXME
     selection_changed();
-#endif //no __WXOSX__ //__WXMSW__
+//#endif //no __WXOSX__ //__WXMSW__
 }
 
 void ObjectList::paste_objects_into_list(const std::vector<size_t>& object_idxs)
@@ -773,9 +773,9 @@ void ObjectList::paste_objects_into_list(const std::vector<size_t>& object_idxs)
     wxGetApp().plater()->changed_objects(object_idxs);
 
     select_items(items);
-#ifndef __WXOSX__ //#ifdef __WXMSW__ // #ys_FIXME
+//#ifndef __WXOSX__ //#ifdef __WXMSW__ // #ys_FIXME
     selection_changed();
-#endif //no __WXOSX__ //__WXMSW__
+//#endif //no __WXOSX__ //__WXMSW__
 }
 
 #ifdef __WXOSX__
@@ -815,7 +815,9 @@ void ObjectList::list_manipulation(bool evt_context_menu/* = false*/)
         if (col == nullptr) {
             if (wxOSX)
                 UnselectAll();
-            else
+            else if (!evt_context_menu) 
+                // Case, when last item was deleted and under GTK was called wxEVT_DATAVIEW_SELECTION_CHANGED,
+                // which invoked next list_manipulation(false)
                 return;
         }
 
@@ -1720,9 +1722,9 @@ void ObjectList::load_subobject(ModelVolumeType type)
     if (sel_item)
         select_item(sel_item);
 
-#ifndef __WXOSX__ //#ifdef __WXMSW__ // #ys_FIXME
+//#ifndef __WXOSX__ //#ifdef __WXMSW__ // #ys_FIXME
     selection_changed();
-#endif //no __WXOSX__ //__WXMSW__
+//#endif //no __WXOSX__ //__WXMSW__
 }
 
 void ObjectList::load_part( ModelObject* model_object,
@@ -1858,9 +1860,9 @@ void ObjectList::load_generic_subobject(const std::string& type_name, const Mode
     const auto object_item = m_objects_model->GetTopParent(GetSelection());
     select_item(m_objects_model->AddVolumeChild(object_item, name, type, 
         new_volume->get_mesh_errors_count()>0));
-#ifndef __WXOSX__ //#ifdef __WXMSW__ // #ys_FIXME
+//#ifndef __WXOSX__ //#ifdef __WXMSW__ // #ys_FIXME
     selection_changed();
-#endif //no __WXOSX__ //__WXMSW__
+//#endif //no __WXOSX__ //__WXMSW__
 }
 
 void ObjectList::load_shape_object(const std::string& type_name)
@@ -1899,6 +1901,9 @@ void ObjectList::load_shape_object(const std::string& type_name)
     new_volume->config.set_key_value("extruder", new ConfigOptionInt(0));
     new_object->invalidate_bounding_box();
 
+    new_object->center_around_origin();
+    new_object->ensure_on_bed();
+
     const BoundingBoxf bed_shape = wxGetApp().plater()->bed_shape_bb();
     new_object->instances[0]->set_offset(Slic3r::to_3d(bed_shape.center().cast<double>(), -new_object->origin_translation(2)));
 

src/slic3r/GUI/Plater.cpp

@@ -3346,7 +3346,7 @@ void Plater::priv::on_slicing_update(SlicingStatusEvent &evt)
         this->statusbar()->set_progress(evt.status.percent);
         this->statusbar()->set_status_text(_(evt.status.text) + wxString::FromUTF8("…"));
     }
-    if (evt.status.flags & (PrintBase::SlicingStatus::RELOAD_SCENE || PrintBase::SlicingStatus::RELOAD_SLA_SUPPORT_POINTS)) {
+    if (evt.status.flags & (PrintBase::SlicingStatus::RELOAD_SCENE | PrintBase::SlicingStatus::RELOAD_SLA_SUPPORT_POINTS)) {
         switch (this->printer_technology) {
         case ptFFF:
             this->update_fff_scene();

xs/xsp/Geometry.xsp

@@ -3,6 +3,7 @@
 %{
 #include <xsinit.h>
 #include "libslic3r/Geometry.hpp"
+#include "libslic3r/ShortestPath.hpp"
 %}
 
 
@@ -49,7 +50,7 @@ std::vector<Points::size_type>
 chained_path(points)
     Points      points
     CODE:
-        Slic3r::Geometry::chained_path(points, RETVAL);
+        RETVAL = chain_points(points);
     OUTPUT:
         RETVAL
 
@@ -58,7 +59,7 @@ chained_path_from(points, start_from)
     Points      points
     Point*      start_from
     CODE:
-        Slic3r::Geometry::chained_path(points, RETVAL, *start_from);
+        RETVAL = chain_points(points, start_from);
     OUTPUT:
         RETVAL