Blender Git Loki

EEVEE: Ambient Occlusion: Refactor

- Fix noise/banding artifact on distant geometry.
- Fix overshadowing on un-occluded surfaces at grazing angle producing "fresnel"
like shadowing. Some of it still appears but this is caused to the low number
of horizons per pixel.
- Improve performance by using a fixed number of samples and fixing the
sampling area size. A better sampling pattern is planned to recover
the lost precision on large AO radius.
- Improved normal reconstruction for the AO pass.
- Improve Bent Normal reconstruction resulting in less faceted look on
smoothed geometry.
- Add Thickness heuristic to avoid overshadowing of thin objects.
Factor is currently hardcoded.
- Add bent normal support to Glossy reflections.
- Change Glossy occlusion to give less light leaks from lightprobes.
It can overshadow on smooth surface but this should be mitigated by
using SSR.
- Use Bent Normal for rough Glossy surfaces.
- Occlusion is now correctly evaluated for each BSDF. However this does make
everything slower. This is mitigated by the fact the search is a lot faster
than before.