This is an improvement on the old spining quad method that was giving artifacts when the reflection ray was nearly aligned with the sphere center.
This might be a bit heavier but it's worth it.
Separate material handling inside another file.
Make use of enums to identify shader variations.
Group all 64*64 LUTs into one array texture.
Only update world probe if world changes.
For now only compute GGX convolution. The GGX LUT used for the split sum approximation (UE4) is merged with the LTX mag LUT that uses the same parameters (theta and roughness)
Using Linear Transform Cosines to compute area lighting. This is far more accurate than other techniques but also slower.
We use rotating quad to mimic sphere area light. For a better approximation, we use a rotating octogon.
