Weird divisor when projecting octahedron probe texture to spherical harmonics.

[Hineven]

Capsaicin/src/core/src/render_techniques/gi10/gi10.comp

Line 1462 in d642e5d

float3 radiance = g_ScreenProbes_ProbeBuffer[probe_pos].xyz / g_ScreenProbesConstants.probe_size;

The line of code above weights the number of hemispherical samples by 1/probe_size when computing SH coefficients for later shading, however the number of samples is probe_size*probe_size. The normalization seems incorrect however if i change the weight to 1/(probe_size*probe_size) the scene seems to be too dark compared to the ray-traced reference.

[Hineven]

Maybe an integral area multiplier (4 x PI) is also missing? And by conicidence 4 x PI (12+) and 1/probe_size (1/8) canceled out making the final shading result about 50% darker than the PT reference. Tone mapping further mitigated the difference.