i can't remember the details anymore but when i tried to convert uvs to texture vectors many years ago (when i experimented with my blender exporter) i used a gauß-seidel solver.

it's not always possible to convert uvs to those texture vectors though. on a mesh with uvs the texture mapping is much more versatile since every vertex can have its own uv coordinate. which can lead to problems with wmp faces with more than 3 sides for example.