>I have an object defined as a bilinear patchmesh and I was to extract the
>polygons that make up this object.
with planar polygons. A bilinear patch mesh is made up of bilinear patches.
A bilinear patch is like a four sided polygon with straight edges except
without the restriction of being planar.
To visualize the concept of non-planarity, grasp a sheet of paper with both
hands. Twist your left hand toward you and your right hand away from you.
The sheet is now non-planar.
If your bilinear patches happen to be planar, you may safely replace them
with four sided polygons. One tricky difference about polygons and bilinear
patches in the RenderMan interface is vertex ordering. Polygon vertices are
specified in clockwise order around the perimeter. Bilinear patch vertices
are specified in "uv" order: upper-left, upper-right, lower-left, lower-right.
I won't go into vertex ordering of meshes here. If you don't have hardcopy
documentation of RiPatchMesh, the spec is online:
Dot C Software, Inc.