Tangent, normal, and visibility cones on Bézier surfaces

Definitions and properties for three types of cones, i.e., tangent, normal and visibility cones for regular parametric surfaces, are provided. Algorithms to compute these cones for a regular B6zier surface are provided. It is shown that a tangent cone can be computed from a hodograph, and a normal cone can be computed from a normal surface of a B6zier surface. It is also shown that a simple transformation converts a normal cone to a visibility cone.