The PhysX libraries assume that the face normal of a triangle with vertices [a,b,c] can be computed as: edge1 = b-a edge2 = c-a face_normal = edge1 x edge2.

Note: This is the same as a counterclockwise winding in a right handed coordinate system or alternatively a clockwise winding order in a left handed coordinate system.

If this does not match the winding order for your triangles, raise the below flag.