Merge pull request #311 from openscad/resize5

Resize5

12 files changed, 352 insertions, 218 deletions

diff --git a/src/CGALEvaluator.cc b/src/CGALEvaluator.cc
index 4deb3b3..7c483cb 100644
--- a/src/CGALEvaluator.cc
+++ b/src/CGALEvaluator.cc
@@ -179,6 +179,64 @@ CGAL_Nef_polyhedron CGALEvaluator::applyHull(const CgaladvNode &node)
 	return N;
 }
 
+CGAL_Nef_polyhedron CGALEvaluator::applyResize(const CgaladvNode &node)
+{
+	// Based on resize() in Giles Bathgate's RapCAD (but not exactly)
+	CGAL_Nef_polyhedron N;
+	N = applyToChildren(node, CGE_UNION);
+
+	if ( N.isNull() || N.isEmpty() ) return N;
+
+	for (int i=0;i<3;i++) {
+		if (node.newsize[i]<0) {
+			PRINT("WARNING: Cannot resize to sizes less than 0.");
+			return N;
+		}
+	}
+
+	CGAL_Iso_cuboid_3 bb;
+
+	if ( N.dim == 2 ) {
+		CGAL_Iso_rectangle_2e bbox = bounding_box( *N.p2 );
+		CGAL_Point_2e min2(bbox.min()), max2(bbox.max());
+		CGAL_Point_3 min3(min2.x(),min2.y(),0), max3(max2.x(),max2.y(),0);
+		bb = CGAL_Iso_cuboid_3( min3, max3 );
+	}
+	else {
+		bb = bounding_box( *N.p3 );
+	}
+
+	Eigen::Matrix<NT,3,1> scale, bbox_size;
+	scale << 1,1,1;
+	bbox_size << bb.xmax()-bb.xmin(), bb.ymax()-bb.ymin(), bb.zmax()-bb.zmin();
+	for (int i=0;i<3;i++) {
+		if (node.newsize[i]) {
+			if (bbox_size[i]==NT(0)) {
+				PRINT("WARNING: Cannot resize in direction normal to flat object");
+				return N;
+			}
+			else {
+				scale[i] = NT(node.newsize[i]) / bbox_size[i];
+			}
+		}
+	}
+	NT autoscale = scale.maxCoeff();
+	for (int i=0;i<3;i++) {
+		if (node.autosize[i]) scale[i] = autoscale;
+	}
+
+	Eigen::Matrix4d t;
+	t << CGAL::to_double(scale[0]),           0,        0,        0,
+	     0,        CGAL::to_double(scale[1]),           0,        0,
+	     0,        0,        CGAL::to_double(scale[2]),           0,
+	     0,        0,        0,                                   1;
+
+	N.transform( Transform3d( t ) );
+	return N;
+}
+
+
+
 /*
 	Typical visitor behavior:
 	o In prefix: Check if we're cached -> prune
@@ -253,57 +311,7 @@ Response CGALEvaluator::visit(State &state, const TransformNode &node)
 				PRINT("Warning: Transformation matrix contains Not-a-Number and/or Infinity - removing object.");
 				N.reset();
 			}
-
-			// Then apply transform
-			// If there is no geometry under the transform, N will be empty
-			// just silently ignore such nodes
-			if (!N.isNull()) {
-				if (N.dim == 2) {
-					// Unfortunately CGAL provides no transform method for CGAL_Nef_polyhedron2
-					// objects. So we convert in to our internal 2d data format, transform it,
-					// tesselate it and create a new CGAL_Nef_polyhedron2 from it.. What a hack!
-					
-					Eigen::Matrix2f testmat;
-					testmat << node.matrix(0,0), node.matrix(0,1), node.matrix(1,0), node.matrix(1,1);
-					if (testmat.determinant() == 0) {
-						PRINT("Warning: Scaling a 2D object with 0 - removing object");
-						N.reset();
-					}
-					else {
-						CGAL_Aff_transformation2 t(
-							node.matrix(0,0), node.matrix(0,1), node.matrix(0,3),
-							node.matrix(1,0), node.matrix(1,1), node.matrix(1,3), node.matrix(3,3));
-						
-						DxfData *dd = N.convertToDxfData();
-						for (size_t i=0; i < dd->points.size(); i++) {
-							CGAL_Kernel2::Point_2 p = CGAL_Kernel2::Point_2(dd->points[i][0], dd->points[i][1]);
-							p = t.transform(p);
-							dd->points[i][0] = to_double(p.x());
-							dd->points[i][1] = to_double(p.y());
-						}
-						
-						PolySet ps;
-						ps.is2d = true;
-						dxf_tesselate(&ps, *dd, 0, true, false, 0);
-						
-						N = evaluateCGALMesh(ps);
-						delete dd;
-					}
-				}
-				else if (N.dim == 3) {
-					if (node.matrix.matrix().determinant() == 0) {
-						PRINT("Warning: Scaling a 3D object with 0 - removing object");
-						N.reset();
-					}
-					else {
-						CGAL_Aff_transformation t(
-							node.matrix(0,0), node.matrix(0,1), node.matrix(0,2), node.matrix(0,3),
-							node.matrix(1,0), node.matrix(1,1), node.matrix(1,2), node.matrix(1,3),
-							node.matrix(2,0), node.matrix(2,1), node.matrix(2,2), node.matrix(2,3), node.matrix(3,3));
-						N.p3->transform(t);
-					}
-				}
-			}
+			N.transform( node.matrix );
 		}
 		else {
 			N = CGALCache::instance()->get(this->tree.getIdString(node));
@@ -358,6 +366,9 @@ Response CGALEvaluator::visit(State &state, const CgaladvNode &node)
 			case HULL:
 				N = applyHull(node);
 				break;
+			case RESIZE:
+				N = applyResize(node);
+				break;
 			}
 		}
 		else {
diff --git a/src/CGALEvaluator.h b/src/CGALEvaluator.h
index 42af5a1..818f520 100644
--- a/src/CGALEvaluator.h
+++ b/src/CGALEvaluator.h
@@ -34,6 +34,7 @@ private:
 	void process(CGAL_Nef_polyhedron &target, const CGAL_Nef_polyhedron &src, CGALEvaluator::CsgOp op);
 	CGAL_Nef_polyhedron applyToChildren(const AbstractNode &node, CGALEvaluator::CsgOp op);
 	CGAL_Nef_polyhedron applyHull(const CgaladvNode &node);
+	CGAL_Nef_polyhedron applyResize(const CgaladvNode &node);
 
 	std::string currindent;
   typedef std::pair<const AbstractNode *, CGAL_Nef_polyhedron> ChildItem;
diff --git a/src/CGAL_Nef_polyhedron.h b/src/CGAL_Nef_polyhedron.h
index d949a2a..cfab993 100644
--- a/src/CGAL_Nef_polyhedron.h
+++ b/src/CGAL_Nef_polyhedron.h
@@ -4,6 +4,7 @@
 #include "cgalfwd.h"
 #include "memory.h"
 #include <string>
+#include "linalg.h"
 
 class CGAL_Nef_polyhedron
 {
@@ -27,7 +28,7 @@ public:
 	int weight() const;
 	class PolySet *convertToPolyset();
 	class DxfData *convertToDxfData() const;
-
+	void transform( const Transform3d &matrix );
 	int dim;
 	shared_ptr<CGAL_Nef_polyhedron2> p2;
 	shared_ptr<CGAL_Nef_polyhedron3> p3;
diff --git a/src/CGAL_Nef_polyhedron_DxfData.cc b/src/CGAL_Nef_polyhedron_DxfData.cc
index 0d0b8f0..0388fe5 100644
--- a/src/CGAL_Nef_polyhedron_DxfData.cc
+++ b/src/CGAL_Nef_polyhedron_DxfData.cc
@@ -29,7 +29,11 @@
 #include "CGAL_Nef_polyhedron.h"
 #include "cgal.h"
 #include "cgalutils.h"
-#include "svg.h"
+#include <boost/variant.hpp>
+#include "polyset.h"
+#include "dxftess.h"
+#include "CGALEvaluator.h"
+#include "Tree.h"
 
 #ifdef ENABLE_CGAL
 
@@ -89,4 +93,59 @@ std::string CGAL_Nef_polyhedron::dump() const
 		return std::string("Nef Polyhedron with dimension != 2 or 3");
 }
 
+
+void CGAL_Nef_polyhedron::transform( const Transform3d &matrix )
+{
+	if (!this->isNull()) {
+		if (this->dim == 2) {
+			// Unfortunately CGAL provides no transform method for CGAL_Nef_polyhedron2
+			// objects. So we convert in to our internal 2d data format, transform it,
+			// tesselate it and create a new CGAL_Nef_polyhedron2 from it.. What a hack!
+			Eigen::Matrix2f testmat;
+			testmat << matrix(0,0), matrix(0,1), matrix(1,0), matrix(1,1);
+			if (testmat.determinant() == 0) {
+				PRINT("Warning: Scaling a 2D object with 0 - removing object");
+				this->reset();
+				return;
+			}
+			else {
+				CGAL_Aff_transformation2 t(
+					matrix(0,0), matrix(0,1), matrix(0,3),
+					matrix(1,0), matrix(1,1), matrix(1,3), matrix(3,3));
+
+				DxfData *dd = this->convertToDxfData();
+				for (size_t i=0; i < dd->points.size(); i++) {
+					CGAL_Kernel2::Point_2 p = CGAL_Kernel2::Point_2(dd->points[i][0], dd->points[i][1]);
+					p = t.transform(p);
+					dd->points[i][0] = to_double(p.x());
+					dd->points[i][1] = to_double(p.y());
+				}
+
+				PolySet ps;
+				ps.is2d = true;
+				dxf_tesselate(&ps, *dd, 0, true, false, 0);
+
+				Tree nulltree;
+				CGALEvaluator tmpeval(nulltree);
+				CGAL_Nef_polyhedron N = tmpeval.evaluateCGALMesh(ps);
+				if ( N.p2 ) this->p2.reset( new CGAL_Nef_polyhedron2( *N.p2 ) );
+				delete dd;
+			}
+		}
+		else if (this->dim == 3) {
+			if (matrix.matrix().determinant() == 0) {
+				PRINT("Warning: Scaling a 3D object with 0 - removing object");
+				this->reset();
+			}
+			else {
+				CGAL_Aff_transformation t(
+					matrix(0,0), matrix(0,1), matrix(0,2), matrix(0,3),
+					matrix(1,0), matrix(1,1), matrix(1,2), matrix(1,3),
+					matrix(2,0), matrix(2,1), matrix(2,2), matrix(2,3), matrix(3,3));
+				this->p3->transform(t);
+			}
+		}
+	}
+}
+
 #endif // ENABLE_CGAL
diff --git a/src/CsgInfo.h b/src/CsgInfo.h
index 37fe0d0..fe953b5 100644
--- a/src/CsgInfo.h
+++ b/src/CsgInfo.h
@@ -57,7 +57,7 @@ public:
 		if (this->root_norm_term) {
 			this->root_chain = new CSGChain();
 			this->root_chain->import(this->root_norm_term);
-			fprintf(stderr, "Normalized CSG tree has %d elements", int(this->root_chain->polysets.size()));
+			PRINTB("Normalized CSG tree has %d elements", int(this->root_chain->polysets.size()));
 		}
 		else {
 			this->root_chain = NULL;
diff --git a/src/OffscreenView.cc b/src/OffscreenView.cc
index 430d4ea..2186eb1 100644
--- a/src/OffscreenView.cc
+++ b/src/OffscreenView.cc
@@ -6,6 +6,7 @@
 #include <string.h>
 #include <cstdlib>
 #include <sstream>
+#include "printutils.h"
 
 OffscreenView::OffscreenView(size_t width, size_t height)
 {
@@ -23,7 +24,7 @@ OffscreenView::~OffscreenView()
 #ifdef ENABLE_OPENCSG
 void OffscreenView::display_opencsg_warning()
 {
-  fprintf(stderr, "OpenSCAD recommended OpenGL version is 2.0. \n");
+  PRINT("OpenSCAD recommended OpenGL version is 2.0.");
 }
 #endif
 
diff --git a/src/PolySetCGALEvaluator.cc b/src/PolySetCGALEvaluator.cc
index 224e657..5976daf 100644
--- a/src/PolySetCGALEvaluator.cc
+++ b/src/PolySetCGALEvaluator.cc
@@ -20,104 +20,6 @@
 #include <boost/foreach.hpp>
 #include <vector>
 
-/*
-
-ZRemover
-
-This class converts one or more already 'flat' 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;
-	shared_ptr<CGAL_Nef_polyhedron2> tmpnef2d;
-	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 ) {
-		log << " <!-- Halffacet visit. Mark: " << hfacet->mark() << " -->\n";
-		if ( hfacet->plane().orthogonal_direction() != this->up ) {
-			log << "  <!-- down-facing half-facet. skipping -->\n";
-			log << " <!-- Halffacet visit end-->\n";
-			return;
-		}
-
-		// possible optimization - throw out facets that are 'side facets' between
-		// the top & bottom of the big thin box. (i.e. mixture of z=-eps and z=eps)
-
-		CGAL_Nef_polyhedron3::Halffacet_cycle_const_iterator fci;
-		int contour_counter = 0;
-		CGAL_forall_facet_cycles_of( fci, hfacet ) {
-			if ( fci.is_shalfedge() ) {
-				CGAL_Nef_polyhedron3::SHalfedge_around_facet_const_circulator c1(fci), cend(c1);
-				std::vector<CGAL_Nef_polyhedron2::Explorer::Point> contour;
-				CGAL_For_all( c1, cend ) {
-					CGAL_Nef_polyhedron3::Point_3 point3d = c1->source()->target()->point();
-					CGAL_Nef_polyhedron2::Explorer::Point point2d( point3d.x(), point3d.y() );
-					contour.push_back( point2d );
-				}
-
-				if (contour.size()==0) continue;
-
-				log << " <!-- is_simple_2:" << CGAL::is_simple_2( contour.begin(), contour.end() ) << " --> \n";
-
-				tmpnef2d.reset( new CGAL_Nef_polyhedron2( contour.begin(), contour.end(), boundary ) );
-
-				if ( contour_counter == 0 ) {
-					log << " <!-- contour is a body. make union(). " << contour.size() << " points. -->\n" ;
-					*(output_nefpoly2d) += *(tmpnef2d);
-				} else {
-					log << " <!-- contour is a hole. make intersection(). " << contour.size() << " points. -->\n";
-					*(output_nefpoly2d) *= *(tmpnef2d);
-				}
-
-				log << "\n<!-- ======== output tmp nef: ==== -->\n"
-					<< OpenSCAD::dump_svg( *tmpnef2d ) << "\n"
-					<< "\n<!-- ======== output accumulator: ==== -->\n"
-					<< OpenSCAD::dump_svg( *output_nefpoly2d ) << "\n";
-
-				contour_counter++;
-			} else {
-				log << " <!-- trivial facet cycle skipped -->\n";
-			}
-		} // next facet cycle (i.e. next contour)
-		log << " <!-- Halffacet visit end -->\n";
-	} // visit()
-};
-
 PolySetCGALEvaluator::PolySetCGALEvaluator(CGALEvaluator &cgalevaluator)
 	: PolySetEvaluator(cgalevaluator.getTree()), cgalevaluator(cgalevaluator)
 {
@@ -186,24 +88,23 @@ PolySet *PolySetCGALEvaluator::evaluatePolySet(const ProjectionNode &node)
 			return NULL;
 		}
 
-		// remove z coordinates to make CGAL_Nef_polyhedron2
 		log << OpenSCAD::svg_header( 480, 100000 ) << "\n";
 		try {
-			ZRemover zremover;
-			CGAL_Nef_polyhedron3::Volume_const_iterator i;
-			CGAL_Nef_polyhedron3::Shell_entry_const_iterator j;
-			CGAL_Nef_polyhedron3::SFace_const_handle sface_handle;
-			for ( i = sum.p3->volumes_begin(); i != sum.p3->volumes_end(); ++i ) {
-				log << "<!-- volume. mark: " << i->mark() << " -->\n";
-				for ( j = i->shells_begin(); j != i->shells_end(); ++j ) {
-					log << "<!-- shell. mark: " << i->mark() << " -->\n";
-					sface_handle = CGAL_Nef_polyhedron3::SFace_const_handle( j );
-					sum.p3->visit_shell_objects( sface_handle , zremover );
-					log << "<!-- shell. end. -->\n";
-				}
-				log << "<!-- volume end. -->\n";
-			}
-			nef_poly.p2 = zremover.output_nefpoly2d;
+      ZRemover zremover;
+      CGAL_Nef_polyhedron3::Volume_const_iterator i;
+      CGAL_Nef_polyhedron3::Shell_entry_const_iterator j;
+      CGAL_Nef_polyhedron3::SFace_const_handle sface_handle;
+      for ( i = sum.p3->volumes_begin(); i != sum.p3->volumes_end(); ++i ) {
+        log << "<!-- volume. mark: " << i->mark() << " -->\n";
+        for ( j = i->shells_begin(); j != i->shells_end(); ++j ) {
+          log << "<!-- shell. mark: " << i->mark() << " -->\n";
+          sface_handle = CGAL_Nef_polyhedron3::SFace_const_handle( j );
+          sum.p3->visit_shell_objects( sface_handle , zremover );
+          log << "<!-- shell. end. -->\n";
+        }
+        log << "<!-- volume end. -->\n";
+      }
+      nef_poly.p2 = zremover.output_nefpoly2d;
 		}	catch (const CGAL::Failure_exception &e) {
 			PRINTB("CGAL error in projection node while flattening: %s", e.what());
 		}
diff --git a/src/cgaladv.cc b/src/cgaladv.cc
index 1773a90..a4cb5ec 100644
--- a/src/cgaladv.cc
+++ b/src/cgaladv.cc
@@ -58,6 +58,9 @@ AbstractNode *CgaladvModule::evaluate(const Context *ctx, const ModuleInstantiat
 	if (type == SUBDIV)
 		argnames += "type", "level", "convexity";
 
+	if (type == RESIZE)
+		argnames += "newsize", "auto";
+
 	Context c(ctx);
 	c.args(argnames, argexpr, inst->argnames, inst->argvalues);
 
@@ -78,6 +81,28 @@ AbstractNode *CgaladvModule::evaluate(const Context *ctx, const ModuleInstantiat
 		level = c.lookup_variable("level", true);
 	}
 
+	if (type == RESIZE) {
+		Value ns = c.lookup_variable("newsize");
+		node->newsize << 0,0,0;
+		if ( ns.type() == Value::VECTOR ) {
+			Value::VectorType vs = ns.toVector();
+			if ( vs.size() >= 1 ) node->newsize[0] = vs[0].toDouble();
+			if ( vs.size() >= 2 ) node->newsize[1] = vs[1].toDouble();
+			if ( vs.size() >= 3 ) node->newsize[2] = vs[2].toDouble();
+		}
+		Value autosize = c.lookup_variable("auto");
+		node->autosize << false, false, false;
+		if ( autosize.type() == Value::VECTOR ) {
+			Value::VectorType va = autosize.toVector();
+			if ( va.size() >= 1 ) node->autosize[0] = va[0].toBool();
+			if ( va.size() >= 2 ) node->autosize[1] = va[1].toBool();
+			if ( va.size() >= 3 ) node->autosize[2] = va[2].toBool();
+		}
+		else if ( autosize.type() == Value::BOOL ) {
+			node->autosize << true, true, true;
+		}
+	}
+
 	node->convexity = (int)convexity.toDouble();
 	node->path = path;
 	node->subdiv_type = subdiv_type.toString();
@@ -112,6 +137,9 @@ std::string CgaladvNode::name() const
 	case HULL:
 		return "hull";
 		break;
+	case RESIZE:
+		return "resize";
+		break;
 	default:
 		assert(false);
 	}
@@ -135,6 +163,13 @@ std::string CgaladvNode::toString() const
 	case HULL:
 		stream << "()";
 		break;
+	case RESIZE:
+		stream << "(newsize = ["
+		  << this->newsize[0] << "," << this->newsize[1] << "," << this->newsize[2] << "]"
+		  << ", auto = ["
+		  << this->autosize[0] << "," << this->autosize[1] << "," << this->autosize[2] << "]"
+		  << ")";
+		break;
 	default:
 		assert(false);
 	}
@@ -148,4 +183,5 @@ void register_builtin_cgaladv()
 	Builtins::init("glide", new CgaladvModule(GLIDE));
 	Builtins::init("subdiv", new CgaladvModule(SUBDIV));
 	Builtins::init("hull", new CgaladvModule(HULL));
+	Builtins::init("resize", new CgaladvModule(RESIZE));
 }
diff --git a/src/cgaladvnode.h b/src/cgaladvnode.h
index 8e769bf..d3aa525 100644
--- a/src/cgaladvnode.h
+++ b/src/cgaladvnode.h
@@ -4,12 +4,14 @@
 #include "node.h"
 #include "visitor.h"
 #include "value.h"
+#include "linalg.h"
 
 enum cgaladv_type_e {
 	MINKOWSKI,
 	GLIDE,
 	SUBDIV,
-	HULL
+	HULL,
+	RESIZE
 };
 
 class CgaladvNode : public AbstractNode
@@ -29,6 +31,8 @@ public:
 	Value path;
 	std::string subdiv_type;
 	int convexity, level;
+	Vector3d newsize;
+	Eigen::Matrix<bool,3,1> autosize;
 	cgaladv_type_e type;
 };
 
diff --git a/src/cgalutils.cc b/src/cgalutils.cc
index 51838df..8b4c476 100644
--- a/src/cgalutils.cc
+++ b/src/cgalutils.cc
@@ -147,7 +147,7 @@ CGAL_Polyhedron *createPolyhedronFromPolySet(const PolySet &ps)
 
 CGAL_Iso_cuboid_3 bounding_box( const CGAL_Nef_polyhedron3 &N )
 {
-	CGAL_Iso_cuboid_3 result(-1,-1,-1,1,1,1);
+	CGAL_Iso_cuboid_3 result(0,0,0,0,0,0);
 	CGAL_Nef_polyhedron3::Vertex_const_iterator vi;
 	std::vector<CGAL_Nef_polyhedron3::Point_3> points;
 	// can be optimized by rewriting bounding_box to accept vertices
@@ -160,7 +160,7 @@ CGAL_Iso_cuboid_3 bounding_box( const CGAL_Nef_polyhedron3 &N )
 
 CGAL_Iso_rectangle_2e bounding_box( const CGAL_Nef_polyhedron2 &N )
 {
-	CGAL_Iso_rectangle_2e result(-1,-1,1,1);
+	CGAL_Iso_rectangle_2e result(0,0,0,0);
 	CGAL_Nef_polyhedron2::Explorer explorer = N.explorer();
 	CGAL_Nef_polyhedron2::Explorer::Vertex_const_iterator vi;
 	std::vector<CGAL_Point_2e> points;
@@ -173,5 +173,56 @@ CGAL_Iso_rectangle_2e bounding_box( const CGAL_Nef_polyhedron2 &N )
 	return result;
 }
 
+void ZRemover::visit( CGAL_Nef_polyhedron3::Halffacet_const_handle hfacet )
+{
+	log << " <!-- ZRemover Halffacet visit. Mark: " << hfacet->mark() << " -->\n";
+	if ( hfacet->plane().orthogonal_direction() != this->up ) {
+		log << "  <!-- ZRemover down-facing half-facet. skipping -->\n";
+		log << " <!-- ZRemover Halffacet visit end-->\n";
+		return;
+	}
+
+	// possible optimization - throw out facets that are vertically oriented
+
+	CGAL_Nef_polyhedron3::Halffacet_cycle_const_iterator fci;
+	int contour_counter = 0;
+	CGAL_forall_facet_cycles_of( fci, hfacet ) {
+		if ( fci.is_shalfedge() ) {
+			log << " <!-- ZRemover Halffacet cycle begin -->\n";
+			CGAL_Nef_polyhedron3::SHalfedge_around_facet_const_circulator c1(fci), cend(c1);
+			std::vector<CGAL_Nef_polyhedron2::Explorer::Point> contour;
+			CGAL_For_all( c1, cend ) {
+				CGAL_Nef_polyhedron3::Point_3 point3d = c1->source()->target()->point();
+				CGAL_Nef_polyhedron2::Explorer::Point point2d( point3d.x(), point3d.y() );
+				contour.push_back( point2d );
+			}
+			if (contour.size()==0) continue;
+
+			log << " <!-- is_simple_2:" << CGAL::is_simple_2( contour.begin(), contour.end() ) << " --> \n";
+
+			tmpnef2d.reset( new CGAL_Nef_polyhedron2( contour.begin(), contour.end(), boundary ) );
+
+			if ( contour_counter == 0 ) {
+				log << " <!-- contour is a body. make union(). " << contour.size() << " points. -->\n" ;
+				*(output_nefpoly2d) += *(tmpnef2d);
+			} else {
+				log << " <!-- contour is a hole. make intersection(). " << contour.size() << " points. -->\n";
+				*(output_nefpoly2d) *= *(tmpnef2d);
+			}
+
+			/*log << "\n<!-- ======== output tmp nef: ==== -->\n"
+				<< OpenSCAD::dump_svg( *tmpnef2d ) << "\n"
+				<< "\n<!-- ======== output accumulator: ==== -->\n"
+				<< OpenSCAD::dump_svg( *output_nefpoly2d ) << "\n";*/
+
+			contour_counter++;
+		} else {
+			log << " <!-- ZRemover trivial facet cycle skipped -->\n";
+		}
+		log << " <!-- ZRemover Halffacet cycle end -->\n";
+	}
+	log << " <!-- ZRemover Halffacet visit end -->\n";
+}
+
 #endif /* ENABLE_CGAL */
 
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
diff --git a/src/svg.cc b/src/svg.cc
index 66e5797..c1231a5 100644
--- a/src/svg.cc
+++ b/src/svg.cc
@@ -2,13 +2,13 @@
 #include "cgalutils.h"
 #include "svg.h"
 #include <boost/algorithm/string.hpp>
+#include <boost/lexical_cast.hpp>
 #include <map>
 
 namespace OpenSCAD {
 
 // SVG code
 // currently for debugging, not necessarily pretty or useful for users. (yet)
-int svg_cursor_py = 0;
 int svg_px_width = SVG_PXW;
 int svg_px_height = SVG_PXH;
 
@@ -27,6 +27,26 @@ std::string svg_label(std::string s)
 	return out.str();
 }
 
+std::string svg_styleblock(std::string strokewidth)
+{
+	std::stringstream out;
+	// halfedge: f1/f0 = face mark, b1/b0 = body or hole, m1/m0 = halfedge mark
+	out << "\
+ <style type='text/css'>\n\
+  .halfedge_f0_b1_m0 { stroke: gold; stroke-width: __STROKEW__px } \n\
+  .halfedge_f0_b1_m1 { stroke: gold; stroke-width: __STROKEW__px } \n\
+  .halfedge_f0_b0_m0 { stroke: green; stroke-width: __STROKEW__px } \n\
+  .halfedge_f0_b0_m1 { stroke: green; stroke-width: __STROKEW__px } \n\
+  .halfedge_f1_b1_m0 { stroke: gold; stroke-width: __STROKEW__px } \n\
+  .halfedge_f1_b1_m1 { stroke: gold; stroke-width: __STROKEW__px } \n\
+  .halfedge_f1_b0_m0 { stroke: green; stroke-width: __STROKEW__px } \n\
+  .halfedge_f1_b0_m1 { stroke: green; stroke-width: __STROKEW__px } \n\
+ </style>";
+	std::string tmp = out.str();
+	boost::replace_all( tmp, "__STROKEW__", strokewidth );
+	return tmp;
+}
+
 std::string svg_border()
 {
 	std::stringstream out;
@@ -93,36 +113,27 @@ std::string dump_cgal_nef_polyhedron2_face_svg(
 	CGAL_Nef_polyhedron2::Explorer::Halfedge_around_face_const_circulator c1,
 	CGAL_Nef_polyhedron2::Explorer::Halfedge_around_face_const_circulator c2,
 	CGAL_Nef_polyhedron2::Explorer explorer,
-	std::string color,
-	bool mark,
-	CGAL_Iso_rectangle_2e bbox )
+	bool facemark, bool body )
 {
+	std::stringstream style;
+	style << "halfedge_f" << facemark << "_b" << body << "_m";
+	std::string styleclass = style.str();
+
   std::stringstream out;
 	CGAL_For_all(c1, c2) {
 		if ( explorer.is_standard( explorer.target(c1) ) ) {
 			CGAL_Point_2e source = explorer.point( explorer.source( c1 ) );
 			CGAL_Point_2e target = explorer.point( explorer.target( c1 ) );
-			CGAL_Point_2e tp1 = project_svg_2to2( source, bbox );
-			CGAL_Point_2e tp2 = project_svg_2to2( target, bbox );
-			double mod=0;
-			if (color=="green") mod=10;
-			out << "      <!-- Halfedge. Mark: " << c1->mark() << " -->\n";
-      out << "       <line"
-			  << " x1='" << CGAL::to_double(tp1.x()) + mod << "'"
-			  << " y1='" << CGAL::to_double(tp1.y()) - mod << "'"
-			  << " x2='" << CGAL::to_double(tp2.x()) + mod << "'"
-			  << " y2='" << CGAL::to_double(tp2.y()) - mod << "'"
-			  << " stroke='" << color << "'";
-			if (!mark) out << " stroke-dasharray='4 4' />\n";
-			else out << " />\n";
-			// crude "arrowhead" to indicate directionality
-			out << "       <circle"
-			  << " cx='" << CGAL::to_double(tp1.x()+ (tp2.x()-tp1.x())* 7/8) + mod << "'"
-			  << " cy='" << CGAL::to_double(tp1.y()+ (tp2.y()-tp1.y())* 7/8) - mod << "'"
-			  << " r='2'"
-			  << " fill='" << color << "' stroke='" << color << "' />\n";
+			out << "    <!-- Halfedge. Mark: " << c1->mark() << " -->\n";
+			std::string he_mark = boost::lexical_cast<std::string>(c1->mark());
+      out << "     <line"
+			  << " x1='" << CGAL::to_double(source.x()) << "'"
+			  << " y1='" << CGAL::to_double(source.y()) << "'"
+			  << " x2='" << CGAL::to_double(target.x()) << "'"
+			  << " y2='" << CGAL::to_double(target.y()) << "'"
+			  << " class='" << styleclass + he_mark << "' />\n";
 		} else {
-			out << "       <!-- 2d Nef Rays - not implemented -->\n";
+			out << "     <!-- 2d Nef Rays - not implemented -->\n";
 		}
 	}
 	return out.str();
@@ -132,27 +143,27 @@ std::string dump_svg( const CGAL_Nef_polyhedron2 &N )
 {
   std::stringstream out;
   CGAL_Nef_polyhedron2::Explorer explorer = N.explorer();
-
 	CGAL_Iso_rectangle_2e bbox = bounding_box( N );
-
   CGAL_Nef_polyhedron2::Explorer::Face_const_iterator i;
-  out << " <svg y='" << svg_cursor_py << "' width='" << svg_px_width
-		<< "' height='" << svg_px_height
-		<< "' xmlns='http://www.w3.org/2000/svg' version='1.1'>\n";
-	out << svg_border() << "\n" << svg_axes() << "\n";
-	svg_cursor_py += svg_px_height;
+
+	std::string linewidth = "0.05";
+
+	out << "<!--CGAL_Nef_polyhedron2 dump begin-->\n";
+	out << svg_header() << "\n" << svg_styleblock( linewidth ) << "\n";
 
 	for ( i = explorer.faces_begin(); i!= explorer.faces_end(); ++i ) {
 			out << "  <!-- face begin. mark: " << i->mark() << "  -->\n";
+			out << "   <!-- body begin -->\n";
 			CGAL_Nef_polyhedron2::Explorer::Halfedge_around_face_const_circulator c1
 				= explorer.face_cycle( i ), c2 ( c1 );
-			out << dump_cgal_nef_polyhedron2_face_svg( c1, c2, explorer, "red", i->mark(), bbox );
+			out << dump_cgal_nef_polyhedron2_face_svg( c1, c2, explorer, i->mark(), true );
+			out << "   <!-- body end -->\n";
 
 		  CGAL_Nef_polyhedron2::Explorer::Hole_const_iterator j;
 			for ( j = explorer.holes_begin( i ); j!= explorer.holes_end( i ); ++j ) {
 				out << "   <!-- hole begin. mark: " << j->mark() << " -->\n";
 				CGAL_Nef_polyhedron2::Explorer::Halfedge_around_face_const_circulator c3( j ), c4 ( c3 );
-				out << dump_cgal_nef_polyhedron2_face_svg( c3, c4, explorer, "green", j->mark(), bbox );
+				out << dump_cgal_nef_polyhedron2_face_svg( c3, c4, explorer, "green", j->mark() );
 				out << "   <!-- hole end -->\n";
 			}
 			out << "  <!-- face end -->\n";
@@ -182,13 +193,13 @@ public:
 	void visit( CGAL_Nef_polyhedron3::Halffacet_const_handle hfacet )
 	{
 		int contour_count = 0;
-		out << "  <!-- Halffacet. Mark: " << (*hfacet).mark() << " -->\n";
+		out << "  <!-- Halffacet visit. Mark: " << (*hfacet).mark() << " -->\n";
 		std::string color = "gold";
 		if (!(*hfacet).mark()) color = "green";
 		CGAL_Nef_polyhedron3::Halffacet_cycle_const_iterator i;
 		CGAL_forall_facet_cycles_of( i, hfacet ) {
 			CGAL_Nef_polyhedron3::SHalfloop_const_handle shl_handle;
-			out << "   <!-- Halffacet cycle: -->\n";
+			out << "   <!-- Halffacet cycle begin: -->\n";
 			if ( contour_count == 0 ) {
 				out << "    <!-- Body contour:--> \n";
 			} else {
@@ -196,13 +207,15 @@ public:
 			}
 			CGAL_Nef_polyhedron3::SHalfedge_around_facet_const_circulator c1(i), c2(c1);
 			CGAL_For_all( c1, c2 ) {
-				out << "     <line";
 				// don't know why we use source()->source(), except thats what CGAL does internally
 				CGAL_Point_3 source = c1->source()->source()->point();
 				CGAL_Point_3 target = c1->source()->target()->point();
 				CGAL_Point_2e tp1 = project_svg_3to2 ( source, bbox );
 				CGAL_Point_2e tp2 = project_svg_3to2 ( target, bbox );
-				out << " "
+        out << "     <!-- " << CGAL::to_double(source.x()) << ","
+          << CGAL::to_double(source.y()) << ","
+          << CGAL::to_double(source.z()) << " -->\n";
+				out << "     <line "
 					<< "x1='" << CGAL::to_double(tp1.x()) << "' "
 					<< "y1='" << CGAL::to_double(tp1.y()) << "' "
 					<< "x2='" << CGAL::to_double(tp2.x()) << "' "
@@ -212,31 +225,34 @@ public:
 				else out << " />\n";
 			}
 			contour_count++;
-		} // next facet cycle (i.e. next contour)
-	} // visit()
-
+			out << "   <!-- Halffacet cycle end -->\n";
+		}
+		out << "  <!-- Halffacet visit end -->\n";
+	}
 };
 
 
 std::string dump_svg( const CGAL_Nef_polyhedron3 &N )
 {
   std::stringstream out;
-	out << svg_header() << "\n" << svg_border() << "\n" << svg_axes() << "\n";
+	std::string linewidth = "0.05";
 	out << "<!--CGAL_Nef_polyhedron3 dump begin-->\n";
+	out << svg_header() << "\n" << svg_border() << "\n";
+	out << svg_styleblock( linewidth ) << "\n" << svg_axes() << "\n";
 
   CGAL_Nef_polyhedron3::Volume_const_iterator c;
   CGAL_forall_volumes(c,N) {
-    out << " <!--Processing volume...-->\n";
+    out << " <!--Volume begin-->\n";
     out << "  <!--Mark: " << (*c).mark() << "-->\n";
     CGAL_Nef_polyhedron3::Shell_entry_const_iterator it;
     CGAL_forall_shells_of(it,c) {
-      out << "  <!--Processing shell...-->\n";
+      out << "  <!--Shell begin-->\n";
       NefPoly3_dumper_svg dumper_svg(N);
       N.visit_shell_objects(CGAL_Nef_polyhedron3::SFace_const_handle(it), dumper_svg );
 			out << dumper_svg.out.str();
-      out << "  <!--Processing shell end-->\n";
+      out << "  <!--Shell end-->\n";
     }
-    out << " <!--Processing volume end-->\n";
+    out << " <!--Volume end-->\n";
   }
   out << "<!--CGAL_Nef_polyhedron3 dump end-->\n";
 	out << "</svg>";