anchor.diff:    new VM.Vector3(-1.0, 0.0, 0.0)
   ];
   
  +/// Returns a GeometryBuilder for Cube with TexUVs and optionally
  +/// Normals.
   GeometryBuilder CubeGeometry(
       {double x: 1.0,
       double y: 1.0,
  
positive.code:   new VM.Vector3(-1.0, 0.0, 0.0)
  ];
  
  // A Wedge is the lower partof a cube that was cut in half
  // through the plane: (-x, y, -z) (-x, y, z), (x, -y, -z), (x, -y, z)
  GeometryBuilder WedgeGeometry(
      {double x: 1.0,
      double y: 1.0,
  
negative.code: part of shape;
  
  final List<VM.Vector3> _CubeNormals = [
    // Front face
    new VM.Vector3(0.0, 0.0, 1.0),
    // Back face
  