show support bridges for the parts of the 2D model below the bottom plane

git-svn-id: https://pycam.svn.sourceforge.net/svnroot/pycam/trunk@955 bbaffbd6-741e-11dd-a85d-61de82d9cad9

src/pycam/Geometry/Model.py

@@ -423,11 +423,13 @@ class ContourModel(BaseModel):
     def get_num_of_lines(self):
         return sum([len(group) for group in self._line_groups])
 
-    def get_polygons(self, z=None):
+    def get_polygons(self, z=None, ignore_below=True):
         if z is None:
             return self._line_groups
-        else:
+        elif ignore_below:
             return [group for group in self._line_groups if group.minz == z]
+        else:
+            return [group for group in self._line_groups if group.minz <= z]
 
     def reverse_directions(self, callback=None):
         for polygon in self._line_groups:

src/pycam/Toolpath/SupportGrid.py

@@ -162,7 +162,7 @@ def get_support_distributed(model, z_plane, average_distance,
         return
     result = Model()
     if hasattr(model, "get_polygons"):
-        polygons = model.get_polygons(z=z_plane)
+        polygons = model.get_polygons(z=z_plane, ignore_below=False)
     else:
         polygons = model.get_waterline_contour(Plane(Point(0, 0, z_plane),
                 Vector(0, 0, 1))).get_polygons()