* Don't do shared vertex colors for every vpaint dot. Profiling on a large mesh showed vpaint spent about 65% of the time in this function, but most of the time no difference will be apparent in the result. (Could make an operator so the user can force this operation after doing some painting.)
TODO:
Profiling now shows most time spent in drawing the mesh. (This is done twice for vpaint, the first time for finding backbuf sampling.)
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