cgalutils.cc

#ifdef ENABLE_CGAL

#include "cgalutils.h"
#include "polyset.h"
#include "cgal.h"

namespace CGALUtils {

/*
	Create a PolySet from a Nef Polyhedron 3. return false on success, 
	true on failure. The trick to this is that Nef Polyhedron3 faces have 
	'holes' in them. . . while PolySet (and many other 3d polyhedron 
	formats) do not allow for holes in their faces. The function documents 
	the method used to deal with this
*/
	bool createPolySetFromNefPolyhedron3(const CGAL_Nef_polyhedron3 &N, PolySet &ps)
	{
		bool err = false;
		CGAL_Nef_polyhedron3::Halffacet_const_iterator hfaceti;
		CGAL_forall_halffacets( hfaceti, N ) {
			CGAL::Plane_3<CGAL_Kernel3> plane( hfaceti->plane() );
			std::vector<CGAL_Polygon_3> polygons;
			// the 0-mark-volume is the 'empty' volume of space. skip it.
			if (hfaceti->incident_volume()->mark()) continue;
			CGAL_Nef_polyhedron3::Halffacet_cycle_const_iterator cyclei;
			CGAL_forall_facet_cycles_of( cyclei, hfaceti ) {
				CGAL_Nef_polyhedron3::SHalfedge_around_facet_const_circulator c1(cyclei);
				CGAL_Nef_polyhedron3::SHalfedge_around_facet_const_circulator c2(c1);
				CGAL_Polygon_3 polygon;
				CGAL_For_all( c1, c2 ) {
					CGAL_Point_3 p = c1->source()->center_vertex()->point();
					polygon.push_back( p );
				}
				polygons.push_back( polygon );
			}

			/* at this stage, we have a sequence of polygons. the first
				 is the "outside edge' or 'body' or 'border', and the rest of the
				 polygons are 'holes' within the first. there are several
				 options here to get rid of the holes. we choose to go ahead
				 and let the tessellater deal with the holes, and then
				 just output the resulting 3d triangles*/
			std::vector<CGAL_Polygon_3> triangles;
			bool err = CGALUtils::tessellate3DFaceWithHoles(polygons, triangles, plane);
			if (!err) {
				for (size_t i=0;i<triangles.size();i++) {
					if (triangles[i].size()!=3) {
						PRINT("WARNING: triangle doesn't have 3 points. skipping");
						continue;
					}
					ps.append_poly();
					for (int j=2;j>=0;j--) {
						double x1,y1,z1;
						x1 = CGAL::to_double(triangles[i][j].x());
						y1 = CGAL::to_double(triangles[i][j].y());
						z1 = CGAL::to_double(triangles[i][j].z());
						ps.append_vertex(x1,y1,z1);
					}
				}
			}
		}
		return err;
	}

}; // namespace CGALUtils

#endif /* ENABLE_CGAL */