Parallelizes implementation for computing the NURBS basis cache.
Removing the unnecessary linear 'find span' search. Due to formulation
of the span find implementation, breakpoints are now evaluated in the
following span rather then in the previous. This does not affect the
point evaluation results, but adjusts how they are computed in the
basis cache.
On top of the threading improvement, removal of the linear search
also means the computational complexity goes from O(n^2) to O(n).
For a very large NURBS curve (250K points), performance is increased
by roughly 40 000 times, and is now interactive!
For cases with large number of small curves. Tests with 25K curves
and 10 control points per curve also indicated a slight performance
improvement, with roughly a 13% reduction in execution time.
Pull Request: https://projects.blender.org/blender/blender/pulls/144000
ffd4c0afb2