* use 80deg rather then 90 for the "Normal" painting option, since painting faces that are very close to 90d to the view gives some artifacts.
* Brecht modified the Barycentric weights function to use a signed area. so BarycentricWeightsSimplePersp2f and BarycentricWeightsSimple2f these funcs are not needed anymore.
2 bugs with seams fixed
* triangle faces seams were not being filled correctly - causing visible seams
* the pretend 3D location for seam pixels was too close to the face edge - causing some pixels to be occluded by the adjacent face.
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