#1867 Fixed problem with vertices having an evil, downscaled-to-float, twin, if a polyhedron contains occasional non-planar polygons

src/polyset-utils.cc

@@ -55,15 +55,11 @@ namespace PolysetUtils {
 		Reindexer<Vector3f> allVertices;
 		std::vector<std::vector<IndexedFace>> polygons;
 
-		for(const auto &pgon : inps.polygons) {
+		for (const auto &pgon : inps.polygons) {
 			if (pgon.size() < 3) {
 				degeneratePolygons++;
 				continue;
 			}
-			if (pgon.size() == 3) { // Short-circuit
-				outps.append_poly(pgon);
-				continue;
-			}
 			
 			polygons.push_back(std::vector<IndexedFace>());
 			std::vector<IndexedFace> &faces = polygons.back();
@@ -86,18 +82,19 @@ namespace PolysetUtils {
 		std::vector<IndexedTriangle> allTriangles;
 		for(const auto &faces : polygons) {
 			std::vector<IndexedTriangle> triangles;
+			bool err = false;
 			if (faces[0].size() == 3) {
 				triangles.push_back(IndexedTriangle(faces[0][0], faces[0][1], faces[0][2]));
 			}
 			else {
-				bool err = GeometryUtils::tessellatePolygonWithHoles(verts, faces, triangles, NULL);
-				if (!err) {
-					for(const auto &t : triangles) {
-						outps.append_poly();
-						outps.append_vertex(verts[t[0]]);
-						outps.append_vertex(verts[t[1]]);
-						outps.append_vertex(verts[t[2]]);
-					}
+				err = GeometryUtils::tessellatePolygonWithHoles(verts, faces, triangles, NULL);
+			}
+			if (!err) {
+				for(const auto &t : triangles) {
+					outps.append_poly();
+					outps.append_vertex(verts[t[0]]);
+					outps.append_vertex(verts[t[1]]);
+					outps.append_vertex(verts[t[2]]);
 				}
 			}
 		}

testdata/scad/3D/issues/issue1867.scad

@@ -0,0 +1,25 @@
+polyhedron(points = [
+[78.1831, 62.349, 10],
+[97.4928, -22.2521, -5],
+[-97.4928, -22.2521, 5],
+[-78.1831, 62.349, -10],
+[78.1831, 62.349, 200],
+[97.4928, -22.2521, 200],
+[-97.4928, -22.2521, 200],
+[-78.1831, 62.349, 200]
+],
+faces = [
+[0, 1, 4],
+[1, 2, 5],
+[2, 3, 6],
+[3, 0, 7],
+[5, 4, 1],
+[6, 5, 2],
+[7, 6, 3],
+[4, 7, 0],
+[4, 5, 6],
+[4, 6, 7],
+
+[3, 2, 1, 0],
+
+]);