projecting it. The original paper suggests to simply interpolate between
the two points of an edge if the distance of the point to that edge is
smaller than a threshold.
* Fixed both 3D and 2D code to utilize this. Possibly other places in
blender where this scaling is done will have to be adjusted.
* Changed vertex interpolation to use 2D interpolation, since it already
did projection on plane and 2d calculations are faster.
* Also added notifier on hard recalc when uvcalc_transfor_correction is
used. Results in instant feedback on UV editor when edge sliding.
c3b5c726c7