Extrusions are also interesting because they allow a designer to specify complex shapes in a simple manner. This proposal is based on the API provided through the freely available tubing and extrusion library. It automatically generates the surface, normals for lighting, and texture coordinates. The Proposal Below follows the proposal. It is preliminary.
Alternate suggestions are welcome.
The spec will be updated in time. The Extrusion node defines the basic extrusion. The other nodes defined below are either special cases of the extrusion ndode, or generalizations. The contour field defines a 2D polyline that represents the cross-section of the extrusion. The contour field must be present, otherwise, an extrusion cannot be drawn.