Fix radiance map settings

[clayjohn]

This PR fixes a bug where the mobile setting for high_quality_ggx was used resulting in extremely low quality radiance maps. It also improves the quality of radiance maps. With an increased quality we can use substantially smaller radiance maps that look even better than the current ones. Accordingly, the default size for radiance maps is decreased to 128 (128 with increased samples produces much higher quality radiance maps than the current setting at 512 and does so much faster).

With these new settings radiance maps will be faster to compute and draw, and will look better. However, existing projects will need to manually decrease radiance_size in all of there skies or else load times will be substantially increased. For this reason I added the "breaks compat" label.

Fixes #21680 and fixes #27422.

[Calinou]

I can confirm a slight performance increase in the Sponza demo and the Material Testers demo 🙂

On a GeForce GTX 1080, I now get 300 FPS in the Material Testers demo compared to 285 FPS with a vanilla binary (built with the same compiler flags).

[akien-mga]

However, existing projects will need to manually decrease radiance_size in all of there skies or else load times will be substantially increased.

I think it's fine, unless people changed the default value to a custom one, it's not saved in the scene file, so existing projects should automatically pick up the new default value AFAIK.

[clayjohn]

@akien-mga That is great news! I'll remove the breaks compat label then.

[akien-mga]

It does "break compat" in that scenes created in 3.1 will look different in 3.2, but any rendering bugfix is bound to induce visual changes, so I think it's ok. It should likely not be backported to 3.1.x, but this kind of behavior changes are expected in 3.2.

[akien-mga]

Thanks!