1 files changed, 54 insertions, 1 deletions

diff --git a/src/cgalutils.h b/src/cgalutils.h
index 9093c3f..6ea7711 100644
--- a/src/cgalutils.h
+++ b/src/cgalutils.h
@@ -2,10 +2,63 @@
 #define CGALUTILS_H_
 
 #include <cgalfwd.h>
-
 class PolySet *createPolySetFromPolyhedron(const CGAL_Polyhedron &p);
 CGAL_Polyhedron *createPolyhedronFromPolySet(const class PolySet &ps);
 CGAL_Iso_cuboid_3 bounding_box( const CGAL_Nef_polyhedron3 &N );
 CGAL_Iso_rectangle_2e bounding_box( const CGAL_Nef_polyhedron2 &N );
 
+#include "svg.h"
+#include "printutils.h"
+
+/*
+
+ZRemover
+
+This class converts one or more Nef3 polyhedra into a Nef2 polyhedron by
+stripping off the 'z' coordinates from the vertices. The resulting Nef2
+poly is accumulated in the 'output_nefpoly2d' member variable.
+
+The 'z' coordinates will either be all 0s, for an xy-plane intersected Nef3,
+or, they will be a mixture of -eps and +eps, for a thin-box intersected Nef3.
+
+Notes on CGAL's Nef Polyhedron2:
+
+1. The 'mark' on a 2d Nef face is important when doing unions/intersections.
+ If the 'mark' of a face is wrong the resulting nef2 poly will be unexpected.
+2. The 'mark' can be dependent on the points fed to the Nef2 constructor.
+ This is why we iterate through the 3d faces using the halfedge cycle
+ source()->target() instead of the ordinary source()->source(). The
+ the latter can generate sequences of points that will fail the
+ the CGAL::is_simple_2() test, resulting in improperly marked nef2 polys.
+3. 3d facets have 'two sides'. we throw out the 'down' side to prevent dups.
+
+The class uses the 'visitor' pattern from the CGAL manual. See also
+http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Nef_3/Chapter_main.html
+http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Nef_3_ref/Class_Nef_polyhedron3.html
+OGL_helper.h
+*/
+
+class ZRemover {
+public:
+	logstream log;
+	CGAL_Nef_polyhedron2::Boundary boundary;
+	boost::shared_ptr<CGAL_Nef_polyhedron2> tmpnef2d;
+	boost::shared_ptr<CGAL_Nef_polyhedron2> output_nefpoly2d;
+	CGAL::Direction_3<CGAL_Kernel3> up;
+	ZRemover()
+	{
+		output_nefpoly2d.reset( new CGAL_Nef_polyhedron2() );
+		boundary = CGAL_Nef_polyhedron2::INCLUDED;
+		up = CGAL::Direction_3<CGAL_Kernel3>(0,0,1);
+		log = logstream(5);
+	}
+	void visit( CGAL_Nef_polyhedron3::Vertex_const_handle ) {}
+	void visit( CGAL_Nef_polyhedron3::Halfedge_const_handle ) {}
+	void visit( CGAL_Nef_polyhedron3::SHalfedge_const_handle ) {}
+	void visit( CGAL_Nef_polyhedron3::SHalfloop_const_handle ) {}
+	void visit( CGAL_Nef_polyhedron3::SFace_const_handle ) {}
+	void visit( CGAL_Nef_polyhedron3::Halffacet_const_handle hfacet );
+};
+
+
 #endif