Solari v7

[JMS55]

This is a major rewrite of Solari.

The old version did DI, diffuse GI, and specular GI / mirror DI in 3 separate passes. Only diffuse rays were resampled, and no rays were traced for cross-domain MIS weight, leading to bias.

This new version is one unified algorithm that handles diffuse and specular DI and GI all in one reservoir. Resampling takes the full BRDF into account, as well as cross-domain visibility in MIS weights.

Advantages:

• Much more accurate
• Much less prone to GI light-leaks
• Improved specular GI quality
• Improved DI quality for nearby lights thanks to BRDF sampling for DI
• Somewhat noisier (don't think this is permanent, it has to do with how I prevent specular correlations)
• Less memory usage

Disadvantage: A bit slower due to the extra rays traced

Showcase

Reference

This PR (with DLSS)

Main (with DLSS)

This PR

Main

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