Algorithm overview - Brixelizer GI
AMD FidelityFX™ Brixelizer GI is a simplified implementation of AMD GI-1.0.
It takes in the G-Buffer resources of your application alongside the output resources from AMD FidelityFX™ Brixelizer to generate Diffuse and Specular GI outputs.

Due to the lack of material information in the distance field from AMD FidelityFX™ Brixelizer, we maintain an internal radiance cache which is populated by the previous frames’ lighting output.
Including just direct lighting will result in 1-bounce diffuse GI, whereas including the composited output from the previous frame gives you multiple bounces effectively for free.
Left: Radiance cache with one bounce, right: Radiance cache with multiple bounces.
Next we spawn screen probes on the visible surfaces in the depth buffer and shoot rays using AMD FidelityFX™ Brixelizer and sample the radiance cache for shading.
These screen probes are then used to feed a world space irradiance cache that stores spherical harmonics probes for each valid brick.
Visualization of screen probes.
Visualization of the irradiance cache.
Finally the outputs are resolved and denoised, leaving you with a Diffuse GI and Specular GI output that you can composite into your final lighting.
Denoised Diffuse GI output.
Denoised Specular GI output.
Final lighting output with GI composited.