Evaluate Activision's new ZH3 Approximation for Diffuse Lighting

[RobertBeckebans]

I chose to store the irradiance data per lightgrid point as 16x16 RGB16F pixels which is 16x16 R11G11B10 = 1024 bytes. It is a very realtime ray tracing friendly design but sucks if you just want baked lighting. It resulted in 6 GB download data of .exr files and if the player plays through the maps they even get decompressed and saved again in the .bimage files which may result in a total extra size of 15 GB. So the GI data is in total over 21 GB.

This new technique promises to store the spherical harmonics of near to quadratic SH3 quality with just 16 bytes.

https://arisilvennoinen.github.io/

There is a also a new SIGGRAPH presentation about the latest Call of Duty lighting:

https://advances.realtimerendering.com/s2024/content/Roughton/SIGGRAPH%20Advances%202024%20-%20Hemispheres%20Presentation%20Notes.pdf

https://www.activision.com/cdn/research/HemiLighting-1.pdf

[RobertBeckebans]

HHD, HLSH, and SH Hemi Multiply
https://www.shadertoy.com/view/lcVSDh

ZH3: Quadratic Zonal Harmonics
https://www.shadertoy.com/view/Xfj3RK

[RobertBeckebans]

The only live talk I could find on this topic:

https://youtu.be/cMo0wFP879U?t=1099