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Commit eb1b785

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EvgeniiGEvgeniiG
committed
Fix specular artifacts for (NdotV < 0)
Cost: 1 VGPR. We clamp NdotV between 0.0001 and 1 as we fill the PreLightData. However, for direct lighting, this changes neither N nor V. Therefore, when we try to use this clamped NdotV value in other geometric calculations, results occasionally make no sense. Caveat: if (NdotV < 0) and (NdotL -> 0), H may point in the opposite hemisphere from N. Clamped XdotH products appear to take care of this issue.
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‎Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.hlsl‎

Copy file name to clipboardExpand all lines: Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.hlsl
+15-11Lines changed: 15 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -503,7 +503,9 @@ void GetBSDFDataDebug(uint paramId, BSDFData bsdfData, inout float3 result, inou
503503
struct PreLightData
504504
{
505505
// General
506-
float NdotV;
506+
float NdotV; // Between 0.0001 and 1
507+
float unNdotV; // Between -1 and 1
508+
507509

508510
// GGX iso
509511
float ggxLambdaV;
@@ -534,9 +536,11 @@ PreLightData GetPreLightData(float3 V, PositionInputs posInput, BSDFData bsdfDat
534536

535537
// General
536538
float3 iblNormalWS = bsdfData.normalWS;
539+
540+
preLightData.unNdotV = dot(bsdfData.normalWS, V);
537541
// GetShiftedNdotV return a positive NdotV
538542
// In case a material use negative normal for double sided lighting like Speedtree they need to do a new calculation
539-
preLightData.NdotV = GetShiftedNdotV(iblNormalWS, V); // Handle artificat for specular lighting
543+
preLightData.NdotV = GetShiftedNdotV(iblNormalWS, V, preLightData.unNdotV);
540544

541545
// GGX iso
542546
preLightData.ggxLambdaV = GetSmithJointGGXLambdaV(preLightData.NdotV, bsdfData.roughness);
@@ -635,7 +639,7 @@ void BSDF( float3 V, float3 L, float3 positionWS, PreLightData preLightData, BS
635639
out float3 specularLighting)
636640
{
637641
float NdotL = saturate(dot(bsdfData.normalWS, L));
638-
float NdotV = preLightData.NdotV;
642+
float NdotV = preLightData.unNdotV; // This value must not be clamped
639643
float LdotV = dot(L, V);
640644
// GCN Optimization: reference PBR Diffuse Lighting for GGX + Smith Microsurfaces
641645
float invLenLV = rsqrt(abs(2.0 * LdotV + 2.0)); // invLenLV = rcp(length(L + V))
@@ -661,12 +665,12 @@ void BSDF( float3 V, float3 L, float3 positionWS, PreLightData preLightData, BS
661665
bsdfData.roughnessB = ClampRoughnessForAnalyticalLights(bsdfData.roughnessB);
662666

663667
#ifdef LIT_USE_BSDF_PRE_LAMBDAV
664-
Vis = V_SmithJointGGXAnisoLambdaV( preLightData.TdotV, preLightData.BdotV, NdotV, TdotL, BdotL, NdotL,
665-
bsdfData.roughnessT, bsdfData.roughnessB, preLightData.anisoGGXLambdaV);
668+
Vis = V_SmithJointGGXAnisoLambdaV(preLightData.TdotV, preLightData.BdotV, preLightData.NdotV, TdotL, BdotL, NdotL,
669+
bsdfData.roughnessT, bsdfData.roughnessB, preLightData.anisoGGXLambdaV);
666670
#else
667671
// TODO: Do comparison between this correct version and the one from isotropic and see if there is any visual difference
668-
Vis = V_SmithJointGGXAniso( preLightData.TdotV, preLightData.BdotV, NdotV, TdotL, BdotL, NdotL,
669-
bsdfData.roughnessT, bsdfData.roughnessB);
672+
Vis = V_SmithJointGGXAniso(preLightData.TdotV, preLightData.BdotV, preLightData.NdotV, TdotL, BdotL, NdotL,
673+
bsdfData.roughnessT, bsdfData.roughnessB);
670674
#endif
671675

672676
D = D_GGXAniso(TdotH, BdotH, NdotH, bsdfData.roughnessT, bsdfData.roughnessB);
@@ -676,9 +680,9 @@ void BSDF( float3 V, float3 L, float3 positionWS, PreLightData preLightData, BS
676680
bsdfData.roughness = ClampRoughnessForAnalyticalLights(bsdfData.roughness);
677681

678682
#ifdef LIT_USE_BSDF_PRE_LAMBDAV
679-
Vis = V_SmithJointGGX(NdotL, NdotV, bsdfData.roughness, preLightData.ggxLambdaV);
683+
Vis = V_SmithJointGGX(NdotL, preLightData.NdotV, bsdfData.roughness, preLightData.ggxLambdaV);
680684
#else
681-
Vis = V_SmithJointGGX(NdotL, NdotV, bsdfData.roughness);
685+
Vis = V_SmithJointGGX(NdotL, preLightData.NdotV, bsdfData.roughness);
682686
#endif
683687
D = D_GGX(NdotH, bsdfData.roughness);
684688
}
@@ -687,9 +691,9 @@ void BSDF( float3 V, float3 L, float3 positionWS, PreLightData preLightData, BS
687691
#ifdef LIT_DIFFUSE_LAMBERT_BRDF
688692
float diffuseTerm = Lambert();
689693
#elif LIT_DIFFUSE_GGX_BRDF
690-
float3 diffuseTerm = DiffuseGGX(bsdfData.diffuseColor, NdotV, NdotL, NdotH, LdotV, bsdfData.perceptualRoughness);
694+
float3 diffuseTerm = DiffuseGGX(bsdfData.diffuseColor, preLightData.NdotV, NdotL, NdotH, LdotV, bsdfData.perceptualRoughness);
691695
#else
692-
float diffuseTerm = DisneyDiffuse(NdotV, NdotL, LdotH, bsdfData.perceptualRoughness);
696+
float diffuseTerm = DisneyDiffuse(preLightData.NdotV, NdotL, LdotH, bsdfData.perceptualRoughness);
693697
#endif
694698

695699
diffuseLighting = bsdfData.diffuseColor * diffuseTerm;
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‎Assets/ScriptableRenderPipeline/ShaderLibrary/CommonLighting.hlsl‎

Copy file name to clipboardExpand all lines: Assets/ScriptableRenderPipeline/ShaderLibrary/CommonLighting.hlsl
+1-2Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -188,9 +188,8 @@ float GetHorizonOcclusion(float3 V, float3 normalWS, float3 vertexNormal, float
188188
// A way to reduce artifact is to limit NdotV value to not be negative and calculate reflection vector for cubemap with a shifted normal (i.e what depends on the view)
189189
// This is what provide this function
190190
// Note: NdotV return by this function is always positive, no need for saturate
191-
float GetShiftedNdotV(inout float3 N, float3 V)
191+
float GetShiftedNdotV(inout float3 N, float3 V, float NdotV)
192192
{
193-
float NdotV = dot(N, V);
194193
const float limit = 0.0001; // Epsilon value that avoid divide by 0 (several BSDF divide by NdotV)
195194

196195
if (NdotV < limit)

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