Add three cached topology maps to `Mesh`, to avoid computations when
mesh data isn't changed. Choosing the right maps to cache is a bit
arbitrary, but generally we have to start somewhere. The limiting
factor is memory usage (all the new caches combined have a
comparable footprint to a UV map).
For now, the caches added are:
- Vertex to face corner
- Vertex to face
- Face corner to face
These caches are used in quite a few places already;
- Face corner normal calculation
- UV value merging
- Setting sharp edges from face angles
- Data transfer modifier
- Voxel remesh attribute remapping
- Sculpt mode painting
- Sculpt mode normal calculation
- Vertex paint mode
- Split edges geometry node
- Mesh topology geometry nodes
Caching topology maps means they don't have to be rebuilt every time
they're used. Meshes copied but without topology changes can share
the cache, further reducing re-computations. For example, FPS with a
large mesh using the "Corners of Vertex" node went from 1.8 to 2.3.
Entering sculpt mode is slightly faster too.
There is some obvious work for future commits:
- Use caches in attribute domain interpolation
- More multithreading of second phase of map building
- Update/build caches eagerly in some geometry nodes
Pull Request: https://projects.blender.org/blender/blender/pulls/107816
4e94db97e2