Enhancement: Implement cubemap convolution to improve reflections

[Montydog9]

What would this enhancement be for?

Rendering

Describe your enhancement suggestion in more detail

With the current system, based on the material roughness a mip from the cubemap is sampled that closely matches that level of reflectance but due to the cubemaps not being prefiltered, the reflections will always look sharp and show visible mipmap artifacts.

Cubemap convolution fixes this by incrementally blurring mipmaps to simulate varying surface roughness, especially high roughness which is very low frequency and should improve the perceived accuracy and quality of reflections.

I'm not a graphics programmer so my knowledge is very limited, but this website goes over it in more detail:

https://learnopengl.com/PBR/IBL/Specular-IBL#:~:text=The%20first%20part%20(when%20convoluted)%20is%20known%20as%20the%20pre%2Dfiltered%20environment%20map