This act in multiple phases:
- A shader scan the whole clipmap after tilemap finalize to gather
where valid tiles from lower LODs are available and write the page
location and LOD offset at invalid tiles location.
- At sampling time we add the LOD offset before the pixel page
modulo operation. This offset is equal to the amount of pages of
the **sampling** LOD needed to have the same modulo result as the
**sampled** LOD.
The whole thing being very tricky, I added a lot of unit testing.
This has no use for now but the system is needed to implement:
- Shadows from Volumetrics at lower cost & memory footprint.
- Fixing soft shadows artifacts.
These will be implemented in separate PRs.
Pull Request: https://projects.blender.org/blender/blender/pulls/120031
7797231c6d