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Fix for artifact with thin-film materials and shadows (#6016)

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* *BackL*.azsli

Signed-off-by: mrieggeramzn <mriegger@amazon.com>

* refactoring from feedback

Signed-off-by: mrieggeramzn <mriegger@amazon.com>
This commit is contained in:
mrieggeramzn
2021-12-02 09:27:01 -08:00
committed by GitHub
parent f4f7f07721
commit bce5e36b53
1 changed files with 14 additions and 2 deletions
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Gems/Atom/Feature/Common/Assets/ShaderLib/Atom/Features/PBR/BackLighting.azsli
+14 -2
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@@ -23,6 +23,16 @@ float3 TransmissionKernel(float t, float3 s)
return 0.25 * (1.0 / exp(exponent) + 3.0 / exp(exponent / 3.0));
}
float ThinObjectFalloff(const float3 surfaceNormal, const float3 dirToLight)
{
const float ndl = saturate(dot(-surfaceNormal, dirToLight));
// ndl works decently well but it can produce a harsh discontinuity in the area just before
// the shadow starts appearing on objects like cylinder and tubes.
// Smoothing out ndl does a decent enough job of removing this artifact.
return smoothstep(0, 1, ndl * ndl);
}
float3 GetBackLighting(Surface surface, LightingData lightingData, float3 lightIntensity, float3 dirToLight, float shadowRatio)
{
float3 result = float3(0.0, 0.0, 0.0);
@@ -53,8 +63,10 @@ float3 GetBackLighting(Surface surface, LightingData lightingData, float3 lightI
float litRatio = 1.0 - shadowRatio;
if (litRatio)
{
result = TransmissionKernel(surface.transmission.thickness * transmissionParams.w, rcp(transmissionParams.xyz)) *
saturate(dot(-surface.normal, dirToLight)) * lightIntensity * litRatio;
const float thickness = surface.transmission.thickness * transmissionParams.w;
const float3 invScattering = rcp(transmissionParams.xyz);
const float falloff = ThinObjectFalloff(surface.normal, dirToLight);
result = TransmissionKernel(thickness, invScattering) * falloff * lightIntensity * litRatio;
}
break;