This first implementation only supports it for Meshes with UV maps, and
only tangents in V direction.
Tangent diffuse:
http://www.blender.org/bf/0001_0080.avi
Tangent spec, diffuse, and bump:
http://www.blender.org/bf/20001_0080.avi
NOTE: since UV coordinates are still very badly subsurfed, this won't work
well for subsurf meshes... on the todo.
On the todo;
- generate tangents for meshes without UV (with some options)
- use tangents from Curve/Surface
- add the Ashkimin shader from tracker
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Important bugfix; curves didn't render anymore since yesterday. :)
485dd1d376