From 15959bc32cc5ba649babac5636bb544e5e46868b Mon Sep 17 00:00:00 2001
From: don bright <hugh.m.bright@gmail.com>
Date: Wed, 22 Aug 2012 12:07:46 +0200
Subject: stop crash bug reported by Giles Bathgate


diff --git a/src/CGALEvaluator.cc b/src/CGALEvaluator.cc
index ac6190f..86be59b 100644
--- a/src/CGALEvaluator.cc
+++ b/src/CGALEvaluator.cc
@@ -150,13 +150,18 @@ CGAL_Nef_polyhedron CGALEvaluator::applyHull(const CgaladvNode &node)
 		}
 		else if (dim == 3) {
 			CGAL_Polyhedron P;
-			chN.p3->convert_to_Polyhedron(P);
-			std::transform(P.vertices_begin(), P.vertices_end(), std::back_inserter(points3d), 
-										 boost::bind(static_cast<const CGAL_Polyhedron::Vertex::Point_3&(CGAL_Polyhedron::Vertex::*)() const>(&CGAL_Polyhedron::Vertex::point), _1));
+			if (!chN.p3->is_simple()) {
+		    PRINT("Object isn't a valid 2-manifold! Please modify your design. See http://en.wikibooks.org/wiki/OpenSCAD_User_Manual/STL_Import_and_Export");
+			}
+			else {
+				chN.p3->convert_to_Polyhedron(P);
+				std::transform(P.vertices_begin(), P.vertices_end(), std::back_inserter(points3d), 
+											 boost::bind(static_cast<const CGAL_Polyhedron::Vertex::Point_3&(CGAL_Polyhedron::Vertex::*)() const>(&CGAL_Polyhedron::Vertex::point), _1));
+			}
 		}
 		chnode->progress_report();
 	}
-	
+
 	if (dim == 2) {
 		std::list<CGAL_Nef_polyhedron2::Point> result;
 		CGAL::convex_hull_2(points2d.begin(), points2d.end(),std:: back_inserter(result));
@@ -165,7 +170,8 @@ CGAL_Nef_polyhedron CGALEvaluator::applyHull(const CgaladvNode &node)
 	}
 	else if (dim == 3) {
 		CGAL_Polyhedron P;
-		CGAL::convex_hull_3(points3d.begin(), points3d.end(), P);
+		if (points3d.size()>3)
+			CGAL::convex_hull_3(points3d.begin(), points3d.end(), P);
 		N = CGAL_Nef_polyhedron(new CGAL_Nef_polyhedron3(P));
 	}
 	return N;
-- 
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