This patch changes the search for unprocessed faces while generating UV-islands from using a flag on faces, to a local N-wide bitfield. It makes no changes to functionality. Local testing on 1.5mio tri meshes gives a 75x speedup (of the code affected, which is the first half of the work).
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The former code would traverse all faces of a mesh until a face was found that had not been processed. This ended up being slow mainly because it had to load face-data to determine the state of the flag. Secondarily, the way it iterated and marked the mesh, it would end up traversing all previously processed faces to find and unprocessed one.
{F10363146}
{F10363147}