Several small speedups for Voronoi node (no behavior change). This
affects Cycles and CPU execution of Voronoi node e.g. in Compositor.
- F1 mode: when evaluating distance for Voronoi cells, use a faster
distance estimation, and only do final distance calculation on the
resulting closest cell. This is only really relevant for the default
Euclidian distance, where this saves a square root per evaluated cell
(in 3D Voronoi case saves 26 square roots; in 4D case saves 80 square
roots).
- N-Sphere Radius mode: speedup by doing squared distance calculations.
We only need to find the closest one, so again doing the square root
per cell is not needed here.
Something like 5%-10% speedup for F1 3D Voronoi; more performance details
in the PR.
Pull Request: https://projects.blender.org/blender/blender/pulls/139490
4a328b5a63