New "rear" seam position

xs/src/libslic3r/BoundingBox.cpp

@@ -183,6 +183,26 @@ BoundingBox3Base<PointClass>::size() const
 }
 template Pointf3 BoundingBox3Base<Pointf3>::size() const;
 
+template <class PointClass> double
+BoundingBoxBase<PointClass>::radius() const
+{
+    double x = this->max.x - this->min.x;
+    double y = this->max.y - this->min.y;
+    return 0.5 * sqrt(x*x+y*y);
+}
+template double BoundingBoxBase<Point>::radius() const;
+template double BoundingBoxBase<Pointf>::radius() const;
+
+template <class PointClass> double
+BoundingBox3Base<PointClass>::radius() const
+{
+    double x = this->max.x - this->min.x;
+    double y = this->max.y - this->min.y;
+    double z = this->max.z - this->min.z;
+    return 0.5 * sqrt(x*x+y*y+z*z);
+}
+template double BoundingBox3Base<Pointf3>::radius() const;
+
 template <class PointClass> void
 BoundingBoxBase<PointClass>::translate(coordf_t x, coordf_t y)
 {

xs/src/libslic3r/BoundingBox.hpp

@@ -29,6 +29,7 @@ class BoundingBoxBase
     void merge(const BoundingBoxBase<PointClass> &bb);
     void scale(double factor);
     PointClass size() const;
+    double radius() const;
     void translate(coordf_t x, coordf_t y);
     void offset(coordf_t delta);
     PointClass center() const;
@@ -48,6 +49,7 @@ class BoundingBox3Base : public BoundingBoxBase<PointClass>
     void merge(const std::vector<PointClass> &points);
     void merge(const BoundingBox3Base<PointClass> &bb);
     PointClass size() const;
+    double radius() const;
     void translate(coordf_t x, coordf_t y, coordf_t z);
     void offset(coordf_t delta);
     PointClass center() const;

xs/src/libslic3r/GCode.cpp

@@ -324,7 +324,7 @@ GCode::extrude(ExtrusionLoop loop, std::string description, double speed)
     Point last_pos = this->last_pos();
     if (this->config.spiral_vase) {
         loop.split_at(last_pos);
-    } else if (seam_position == spNearest || seam_position == spAligned) {
+    } else if (seam_position == spNearest || seam_position == spAligned || seam_position == spRear) {
         const Polygon polygon = loop.polygon();
         
         // simplify polygon in order to skip false positives in concave/convex detection
@@ -354,8 +354,13 @@ GCode::extrude(ExtrusionLoop loop, std::string description, double speed)
         }
         
         // retrieve the last start position for this object
-        if (this->layer != NULL && this->_seam_position.count(this->layer->object()) > 0) {
+        if (this->layer != NULL) {
-            last_pos = this->_seam_position[this->layer->object()];
+            if (seam_position == spRear) {
+                last_pos = this->layer->object()->bounding_box().center();
+                last_pos.y += coord_t(3. * this->layer->object()->bounding_box().radius());
+            } else if (this->_seam_position.count(this->layer->object()) > 0) {
+                last_pos = this->_seam_position[this->layer->object()];
+            }
         }
         
         Point point;
@@ -392,6 +397,7 @@ GCode::extrude(ExtrusionLoop loop, std::string description, double speed)
             last_pos = Point(polygon.bounding_box().max.x, centroid.y);
             last_pos.rotate(fmod((float)rand()/16.0, 2.0*PI), centroid);
         }
+        // Find the closest point, avoid overhangs.
         loop.split_at(last_pos, true);
     }
     

xs/src/libslic3r/PrintConfig.cpp

@@ -943,9 +943,11 @@ PrintConfigDef::PrintConfigDef()
     def->enum_values.push_back("random");
     def->enum_values.push_back("nearest");
     def->enum_values.push_back("aligned");
+    def->enum_values.push_back("rear");
     def->enum_labels.push_back("Random");
     def->enum_labels.push_back("Nearest");
     def->enum_labels.push_back("Aligned");
+    def->enum_labels.push_back("Rear");
     def->default_value = new ConfigOptionEnum<SeamPosition>(spAligned);
 
     def = this->add("serial_port", coString);

xs/src/libslic3r/PrintConfig.hpp

@@ -41,7 +41,7 @@ enum SupportMaterialPattern {
 };
 
 enum SeamPosition {
-    spRandom, spNearest, spAligned
+    spRandom, spNearest, spAligned, spRear
 };
 
 template<> inline t_config_enum_values ConfigOptionEnum<GCodeFlavor>::get_enum_values() {
@@ -89,6 +89,7 @@ template<> inline t_config_enum_values ConfigOptionEnum<SeamPosition>::get_enum_
     keys_map["random"]              = spRandom;
     keys_map["nearest"]             = spNearest;
     keys_map["aligned"]             = spAligned;
+    keys_map["rear"]                = spRear;
     return keys_map;
 }