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Fix D_GGX code which can cause divide-by-zero val 

When given roughness is lower than 0.01, d value in original code will
be zero. This can make last return value as NAN because of
divide-by-zero. This is well addressed in issue #56373.

Modified code is referenced on D_GGX function of google/filament
(https://github.com/google/filament/blob/main/shaders/src/brdf.fs#L54-L79)

Signed-off-by: snowapril <sinjihng@gmail.com>
This commit is contained in:
snowapril 2022-03-14 09:32:06 +09:00
parent 7a454842d4
commit b6f72f2b4a
1 changed files with 3 additions and 3 deletions
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6
servers/rendering/renderer_rd/shaders/scene_forward_lights_inc.glsl
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@ -1,9 +1,9 @@
// Functions related to lighting
float D_GGX(float cos_theta_m, float alpha) {
float alpha2 = alpha * alpha;
float d = 1.0 + (alpha2 - 1.0) * cos_theta_m * cos_theta_m;
return alpha2 / (M_PI * d * d);
float a = cos_theta_m * alpha;
float k = alpha / (1.0 - cos_theta_m * cos_theta_m + a * a);
return k * k * (1.0 / M_PI);
}
// From Earl Hammon, Jr. "PBR Diffuse Lighting for GGX+Smith Microsurfaces" https://www.gdcvault.com/play/1024478/PBR-Diffuse-Lighting-for-GGX