``` *      The whole triangle   X
*      represents the      / \
*      new bevel face.    /   \
*                        /     \
*       Split into      /       \
*       a quad fan.    /         \
*                     /           \
*                    /             \
*                   /               \
*          co_prev +-.             .-+
*                 /   `-._     _.-'   \
*                / co_cent`-+-'        \
*               /           |           \
* Quad of      /            |            \
* interest -- / ---> X      |             \
*            /              |              \
*           /               |               \
*          /         co_next|                \
* co_orig +-----------------+-----------------+
*
*         For each quad, calcualte UV's based on the following:
*           U = k    / (vm->seg * 2)
*           V = ring / (vm->seg * 2)
*           quad = (co_orig, co_prev, co_cent, co_next)
*           ... note that co_cent is the same for all quads in the fan.
* ```