Reference:Finite Patch Primitives

There are six totally thin, finite objects which have no well-defined inside. They are bicubic patch, disc, smooth triangle, triangle, polygon, mesh, and mesh2. They may be combined in CSG union, but cannot be used inside a clipped_by statement.

Note: Patch objects may give unexpected results when used in differences and intersections.

These conditions apply:

1. Solids may be differenced from bicubic patches with the expected results.
2. Differencing a bicubic patch from a solid may give unexpected results.
• Especially if the inverse keyword is used!
3. Intersecting a solid and a bicubic patch will give the expected results.
• The parts of the patch that intersect the solid object will be visible.
4. Merging a solid and a bicubic patch will remove the parts of the bicubic patch that intersect the solid.

Because these types are finite POV-Ray can use automatic bounding on them to speed up rendering time. As with all shapes they can be translated, rotated and scaled.