#1368 fix layerset folding: check length thichkness ratio

src/ifcgeom/IfcGeomFunctions.cpp

@@ -2600,6 +2600,8 @@ bool IfcGeom::Kernel::fold_layers(const IfcSchema::IfcWall* wall, const IfcRepre
 		}
 	}
 
+	const double total_thickness = std::accumulate(thicknesses.begin(), thicknesses.end(), 0.);
+
 	gp_Pnt own_axis_start, own_axis_end;
 	find_wall_end_points(wall, own_axis_start, own_axis_end);
 
@@ -2661,6 +2663,16 @@ bool IfcGeom::Kernel::fold_layers(const IfcSchema::IfcWall* wall, const IfcRepre
 	}
 	*/
 
+	const double length_required = endpoint_connections.size() * total_thickness;
+	// @todo this is not precisely the distance in case of curved walls. Also, it's safer
+	// to first reproject the body onto the axis to get the precise curve parametrization
+	// range. It's only a safeguard though, so can probably be approximated.
+	const double axis_length = own_axis_start.Distance(own_axis_end);
+	if (length_required > axis_length) {
+		Logger::Warning("The wall axis is not long enough to accomodate the fold points");
+		return false;
+	}
+
 	for (endpoint_connections_t::const_iterator it = endpoint_connections.begin(); it != endpoint_connections.end(); ++it) {
 		IfcSchema::IfcConnectionTypeEnum::Value connection_type = it->first.first;
 
@@ -2746,8 +2758,6 @@ bool IfcGeom::Kernel::fold_layers(const IfcSchema::IfcWall* wall, const IfcRepre
 		
 		double layer_offset = 0;
 
-		const double total_thickness = std::accumulate(thicknesses.begin(), thicknesses.end(), 0.);
-		
 		std::vector<double>::const_iterator thickness = thicknesses.begin();
 		result_t::iterator result_vector = result.begin() + 1;
 
@@ -2778,7 +2788,8 @@ bool IfcGeom::Kernel::fold_layers(const IfcSchema::IfcWall* wall, const IfcRepre
 				surface->D1(u, v, Ps, Vs1, Vs2);
 				Vs1.Cross(Vs2);
 
-				if (Vs1.IsParallel(Vc, 1.e-5)) {
+				if (Vs1.IsNormal(Vc, 1.e-5)) {
+					int a = 1;
 					Logger::Warning("Connected walls are parallel");
 					parallel = true;
 				} else if (w < axis_u1 || w > axis_u2) {