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This makes it available in Cycles standalone, and the implementation can be shared with Blender. This also makes it possible to compute tangents after tessellation for adaptive subdivision. There is a difference in UV map tangents when there are no UVs. They are now generated from object space coordinates instead of auto texture space coordinates. This is more efficient, and a corner case that we don't have to keep compatible. Co-authored-by: Brecht Van Lommel <brecht@blender.org> Pull Request: https://projects.blender.org/blender/cycles/pulls/25