New sparse infill: "stars" - David's star shaped infill.

This is very similar to a "triangles" infill, but maximum two lines
intersect at a single point.

added utility function get_extents_vector()

xs/src/libslic3r/ExPolygon.cpp

@@ -587,6 +587,15 @@ BoundingBox get_extents_rotated(const ExPolygons &expolygons, double angle)
     return bbox;
 }
 
+extern std::vector<BoundingBox> get_extents_vector(const ExPolygons &polygons)
+{
+    std::vector<BoundingBox> out;
+    out.reserve(polygons.size());
+    for (ExPolygons::const_iterator it = polygons.begin(); it != polygons.end(); ++ it)
+        out.push_back(get_extents(*it));
+    return out;
+}
+
 bool remove_sticks(ExPolygon &poly)
 {
     return remove_sticks(poly.contour) || remove_sticks(poly.holes);

xs/src/libslic3r/ExPolygon.hpp

@@ -271,6 +271,7 @@ extern BoundingBox get_extents(const ExPolygon &expolygon);
 extern BoundingBox get_extents(const ExPolygons &expolygons);
 extern BoundingBox get_extents_rotated(const ExPolygon &poly, double angle);
 extern BoundingBox get_extents_rotated(const ExPolygons &polygons, double angle);
+extern std::vector<BoundingBox> get_extents_vector(const ExPolygons &polygons);
 
 extern bool        remove_sticks(ExPolygon &poly);
 

xs/src/libslic3r/Fill/FillBase.cpp

@@ -25,6 +25,7 @@ Fill* Fill::new_from_type(const InfillPattern type)
     case ipLine:                return new FillLine();
     case ipGrid:                return new FillGrid2();
     case ipTriangles:           return new FillTriangles();
+    case ipStars:               return new FillStars();
     case ipCubic:               return new FillCubic();
 //  case ipGrid:                return new FillGrid();
     case ipArchimedeanChords:   return new FillArchimedeanChords();

xs/src/libslic3r/Fill/FillBase.hpp

@@ -49,7 +49,7 @@ public:
     // in radians, ccw, 0 = East
     float       angle;
     // In scaled coordinates. Maximum lenght of a perimeter segment connecting two infill lines.
-    // Used by the FillRectilinear2, FillGrid2, FillTriangles and FillCubic.
+    // Used by the FillRectilinear2, FillGrid2, FillTriangles, FillStars and FillCubic.
     // If left to zero, the links will not be limited.
     coord_t     link_max_length;
     // In scaled coordinates. Used by the concentric infill pattern to clip the loops to create extrusion paths.

xs/src/libslic3r/Fill/FillRectilinear2.cpp

@@ -1517,12 +1517,26 @@ Polylines FillTriangles::fill_surface(const Surface *surface, const FillParams &
     Polylines polylines_out;
     if (! fill_surface_by_lines(surface, params2, 0.f, 0., polylines_out) ||
         ! fill_surface_by_lines(surface, params2, float(M_PI / 3.), 0., polylines_out) ||
-        ! fill_surface_by_lines(surface, params2, float(2. * M_PI / 3.), 0., polylines_out)) {
+        ! fill_surface_by_lines(surface, params2, float(2. * M_PI / 3.), 0.5 * this->spacing / params2.density, polylines_out)) {
         printf("FillTriangles::fill_surface() failed to fill a region.\n");
     }
     return polylines_out;
 }
 
+Polylines FillStars::fill_surface(const Surface *surface, const FillParams &params)
+{
+    // Each linear fill covers 1/3 of the target coverage.
+    FillParams params2 = params;
+    params2.density *= 0.333333333f;
+    Polylines polylines_out;
+    if (! fill_surface_by_lines(surface, params2, 0.f, 0., polylines_out) ||
+        ! fill_surface_by_lines(surface, params2, float(M_PI / 3.), 0., polylines_out) ||
+        ! fill_surface_by_lines(surface, params2, float(2. * M_PI / 3.), 0., polylines_out)) {
+        printf("FillStars::fill_surface() failed to fill a region.\n");
+    }
+    return polylines_out;
+}
+
 Polylines FillCubic::fill_surface(const Surface *surface, const FillParams &params)
 {
     // Each linear fill covers 1/3 of the target coverage.

xs/src/libslic3r/Fill/FillRectilinear2.hpp

@@ -41,6 +41,17 @@ protected:
     virtual float _layer_angle(size_t idx) const { return 0.f; }
 };
 
+class FillStars : public FillRectilinear2
+{
+public:
+    virtual ~FillStars() {}
+    virtual Polylines fill_surface(const Surface *surface, const FillParams &params);
+
+protected:
+    // The grid fill will keep the angle constant between the layers, see the implementation of Slic3r::Fill.
+    virtual float _layer_angle(size_t idx) const { return 0.f; }
+};
+
 class FillCubic : public FillRectilinear2
 {
 public:

xs/src/libslic3r/Polygon.cpp

@@ -328,6 +328,15 @@ BoundingBox get_extents_rotated(const Polygons &polygons, double angle)
     return bb;
 }
 
+extern std::vector<BoundingBox> get_extents_vector(const Polygons &polygons)
+{
+    std::vector<BoundingBox> out;
+    out.reserve(polygons.size());
+    for (Polygons::const_iterator it = polygons.begin(); it != polygons.end(); ++ it)
+        out.push_back(get_extents(*it));
+    return out;
+}
+
 static inline bool is_stick(const Point &p1, const Point &p2, const Point &p3)
 {
     Point v1 = p2 - p1;

xs/src/libslic3r/Polygon.hpp

@@ -52,6 +52,7 @@ extern BoundingBox get_extents(const Polygon &poly);
 extern BoundingBox get_extents(const Polygons &polygons);
 extern BoundingBox get_extents_rotated(const Polygon &poly, double angle);
 extern BoundingBox get_extents_rotated(const Polygons &polygons, double angle);
+extern std::vector<BoundingBox> get_extents_vector(const Polygons &polygons);
 
 // Remove sticks (tentacles with zero area) from the polygon.
 extern bool        remove_sticks(Polygon &poly);

xs/src/libslic3r/PrintConfig.cpp

@@ -397,6 +397,7 @@ PrintConfigDef::PrintConfigDef()
     def->enum_values.push_back("rectilinear");
     def->enum_values.push_back("grid");
     def->enum_values.push_back("triangles");
+    def->enum_values.push_back("stars");
     def->enum_values.push_back("cubic");
     def->enum_values.push_back("line");
     def->enum_values.push_back("concentric");
@@ -408,6 +409,7 @@ PrintConfigDef::PrintConfigDef()
     def->enum_labels.push_back("Rectilinear");
     def->enum_labels.push_back("Grid");
     def->enum_labels.push_back("Triangles");
+    def->enum_labels.push_back("Stars");
     def->enum_labels.push_back("Cubic");
     def->enum_labels.push_back("Line");
     def->enum_labels.push_back("Concentric");

xs/src/libslic3r/PrintConfig.hpp

@@ -30,7 +30,7 @@ enum GCodeFlavor {
 };
 
 enum InfillPattern {
-    ipRectilinear, ipGrid, ipTriangles, ipCubic, ipLine, ipConcentric, ipHoneycomb, ip3DHoneycomb,
+    ipRectilinear, ipGrid, ipTriangles, ipStars, ipCubic, ipLine, ipConcentric, ipHoneycomb, ip3DHoneycomb,
     ipHilbertCurve, ipArchimedeanChords, ipOctagramSpiral,
 };
 
@@ -59,6 +59,7 @@ template<> inline t_config_enum_values ConfigOptionEnum<InfillPattern>::get_enum
     keys_map["rectilinear"]         = ipRectilinear;
     keys_map["grid"]                = ipGrid;
     keys_map["triangles"]           = ipTriangles;
+    keys_map["stars"]               = ipStars;
     keys_map["cubic"]               = ipCubic;
     keys_map["line"]                = ipLine;
     keys_map["concentric"]          = ipConcentric;