3D viewer: Modify yhe way board items shapes are built:

* All items shapes  are converted to polygons.
* Polygons are merged layer by layer (for calculation time reasons,zones are not merged)
* for copper layers, vias and pads holes are substracted from polygons (but, for calculation time reasons,  not inside zones areas).
* the look is better, mainly when displaying the copper thickness
* solder and paste layers are now shown in 3D viewer.
* the code was seriously cleaned (but still needs to be enhanced).
* Note this is a work in progress which needs refinements.

pcbnew/zone_filling_algorithm.cpp

@@ -38,8 +38,24 @@
 #include <pcbnew.h>
 #include <zones.h>
 
+/* Build the filled solid areas data from real outlines (stored in m_Poly)
+ * The solid areas can be more than one on copper layers, and do not have holes
+  ( holes are linked by overlapping segments to the main outline)
+ * aPcb: the current board (can be NULL for non copper zones)
+ * aCornerBuffer: A reference to a buffer to store polygon corners, or NULL
+ * if NULL:
+ * - m_FilledPolysList is used to store solid areas polygons.
+ * - on copper layers, tracks and other items shapes of other nets are
+ * removed from solid areas
+ * if not null:
+ * Only the zone outline (with holes, if any) are stored in aCornerBuffer
+ * with holes linked. Therfore only one polygon is created
+ * This function calls AddClearanceAreasPolygonsToPolysList()
+ * to add holes for pads and tracks and other items not in net.
+ */
 
-int ZONE_CONTAINER::BuildFilledPolysListData( BOARD* aPcb, std::vector <CPolyPt>* aCornerBuffer )
+bool ZONE_CONTAINER::BuildFilledSolidAreasPolygons( BOARD* aPcb,
+                            std::vector <CPolyPt>* aCornerBuffer )
 {
     if( aCornerBuffer == NULL )
         m_FilledPolysList.clear();