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fix: add checks to prevent NaN for BRDFs #1226

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Merged
alandtse merged 2 commits into from
Jul 2, 2025
Merged

fix: add checks to prevent NaN for BRDFs #1226

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0002942
fix: add checks to prevent NaN for BRDFs
jiayev Jul 1, 2025
c050e67
use defined epsilon
jiayev Jul 2, 2025
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2 changes: 1 addition & 1 deletion features/Hair Specular/Shaders/Hair/Hair.hlsli
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Original file line number Diff line number Diff line change
Expand Up @@ -96,7 +96,7 @@ namespace Hair

const float3 Lp = L - NdotL * N;
const float3 Vp = V - NdotL * N;
const float cosPhi = dot(Lp, Vp) * rsqrt(dot(Lp, Lp) * dot(Vp, Vp) + 1e-4);
const float cosPhi = dot(Lp, Vp) * rsqrt(dot(Lp, Lp) * dot(Vp, Vp) + EPSILON_DIVISION);
const float cosHalfPhi = sqrt(saturate(0.5 + 0.5 * cosPhi));

float n_prime = 1.19 / cosThetaD + 0.36 * cosThetaD;
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20 changes: 10 additions & 10 deletions package/Shaders/Common/BRDF.hlsli
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Expand Up @@ -41,7 +41,7 @@ namespace BRDF

float2 cos_alpha_beta = NdotV < NdotL ? float2(NdotV, NdotL) : float2(NdotL, NdotV);
float2 sin_alpha_beta = sqrt(saturate(1.0 - cos_alpha_beta * cos_alpha_beta));
float C = sin_alpha_beta.x * sin_alpha_beta.y / (1e-6 + cos_alpha_beta.y);
float C = sin_alpha_beta.x * sin_alpha_beta.y / (EPSILON_DIVISION + cos_alpha_beta.y);

return (1 / Math::PI) * (A + B * max(0.0, gamma) * C);
}
Expand Down Expand Up @@ -131,10 +131,10 @@ namespace BRDF
// [Estevez et al. 2017, "Production Friendly Microfacet Sheen BRDF"]
float D_Charlie(float roughness, float NdotH)
{
float invAlpha = pow(roughness, -4);
float invAlpha = pow(abs(roughness), -4);
float cos2h = NdotH * NdotH;
float sin2h = max(1.0 - cos2h, 1e-5);
return (2.0 + invAlpha) * pow(sin2h, invAlpha * 0.5) / Math::TAU;
float sin2h = 1.0 - cos2h;
return (2.0 + invAlpha) * pow(abs(sin2h), invAlpha * 0.5) / Math::TAU;
}

// Smith term for GGX
Expand All @@ -145,7 +145,7 @@ namespace BRDF
float a2 = a * a;
float Vis_SmithV = NdotV + sqrt(a2 + (1.0 - a2) * NdotV * NdotV);
float Vis_SmithL = NdotL + sqrt(a2 + (1.0 - a2) * NdotL * NdotL);
return rcp(Vis_SmithV * Vis_SmithL);
return rcp(max(Vis_SmithV * Vis_SmithL, EPSILON_DIVISION));
}

// Appoximation of joint Smith term for GGX
Expand All @@ -155,7 +155,7 @@ namespace BRDF
float a = roughness * roughness;
float Vis_SmithV = NdotL * (NdotV * (1.0 + a) + a);
float Vis_SmithL = NdotV * (NdotL * (1.0 + a) + a);
return rcp(Vis_SmithV + Vis_SmithL) * 0.5;
return rcp(max(Vis_SmithV + Vis_SmithL, EPSILON_DIVISION)) * 0.5;
}

float Vis_SmithJoint(float roughness, float NdotV, float NdotL)
Expand All @@ -164,14 +164,14 @@ namespace BRDF
float a2 = a * a;
float Vis_SmithV = NdotL * sqrt(a2 + (1.0 - a2) * NdotV * NdotV);
float Vis_SmithL = NdotV * sqrt(a2 + (1.0 - a2) * NdotL * NdotL);
return rcp(Vis_SmithV + Vis_SmithL) * 0.5;
return rcp(max(Vis_SmithV + Vis_SmithL, EPSILON_DIVISION)) * 0.5;
}

float Vis_SmithJointAniso(float alphaX, float alphaY, float NdotL, float NdotV, float XdotL, float YdotL, float XdotV, float YdotV)
{
float Vis_SmithV = NdotL * length(float3(alphaX * XdotV, alphaY * YdotV, NdotV));
float Vis_SmithL = NdotV * length(float3(alphaX * XdotL, alphaY * YdotL, NdotL));
return rcp(Vis_SmithV + Vis_SmithL) * 0.5;
return rcp(max(Vis_SmithV + Vis_SmithL, EPSILON_DIVISION)) * 0.5;
}

// [Estevez and Kulla 2017, "Production Friendly Microfacet Sheen BRDF"]
Expand All @@ -192,13 +192,13 @@ namespace BRDF
{
float visV = NdotV < 0.5 ? exp(Vis_Charlie_L(NdotV, roughness)) : exp(2.0 * Vis_Charlie_L(0.5, roughness) - Vis_Charlie_L(1.0 - NdotV, roughness));
float visL = NdotL < 0.5 ? exp(Vis_Charlie_L(NdotL, roughness)) : exp(2.0 * Vis_Charlie_L(0.5, roughness) - Vis_Charlie_L(1.0 - NdotL, roughness));
return rcp(((1.0 + visV + visL) * (4.0 * NdotL * NdotV)));
return rcp(((1.0 + visV + visL) * max(4.0 * NdotL * NdotV, EPSILON_DIVISION)));
}

// [Neubelt et al. 2013, "Crafting a Next-gen Material Pipeline for The Order: 1886"]
float Vis_Neubelt(float NdotV, float NdotL)
{
return rcp(4.0 * (NdotL + NdotV - NdotL * NdotV));
return rcp(4.0 * max(NdotL + NdotV - NdotL * NdotV, EPSILON_DIVISION));
}

// [Lazarov 2013, "Getting More Physical in Call of Duty: Black Ops II"]
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3 changes: 3 additions & 0 deletions package/Shaders/Common/Math.hlsli
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Original file line number Diff line number Diff line change
@@ -1,6 +1,9 @@
#ifndef __MATH_DEPENDENCY_HLSL__
#define __MATH_DEPENDENCY_HLSL__

#define EPSILON_DOT_CLAMP 1e-5f // For dot product clamping
#define EPSILON_DIVISION 1e-6f // For division to avoid division by zero

namespace Math
{
static const float4x4 IdentityMatrix = {
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16 changes: 8 additions & 8 deletions package/Shaders/Common/PBR.hlsli
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Original file line number Diff line number Diff line change
Expand Up @@ -216,7 +216,7 @@ namespace PBR

const float3 Lp = L - NdotL * N;
const float3 Vp = V - NdotL * N;
const float cosPhi = dot(Lp, Vp) * rsqrt(dot(Lp, Lp) * dot(Vp, Vp) + 1e-4);
const float cosPhi = dot(Lp, Vp) * rsqrt(dot(Lp, Lp) * dot(Vp, Vp) + EPSILON_DIVISION);
const float cosHalfPhi = sqrt(saturate(0.5 + 0.5 * cosPhi));

float n_prime = 1.19 / cosThetaD + 0.36 * cosThetaD;
Expand Down Expand Up @@ -309,8 +309,8 @@ namespace PBR
float NdotH = dot(N, H);
float VdotH = dot(V, H);

float satNdotL = clamp(NdotL, 1e-5, 1);
float satNdotV = saturate(abs(NdotV) + 1e-5);
float satNdotL = clamp(NdotL, EPSILON_DOT_CLAMP, 1);
float satNdotV = saturate(abs(NdotV) + EPSILON_DOT_CLAMP);
float satVdotL = saturate(VdotL);
float satNdotH = saturate(NdotH);
float satVdotH = saturate(VdotH);
Expand Down Expand Up @@ -364,8 +364,8 @@ namespace PBR
float coatVdotH = satVdotH;
[branch] if ((PBRFlags & Flags::CoatNormal) != 0)
{
coatNdotL = clamp(dot(coatN, coatL), 1e-5, 1);
coatNdotV = saturate(abs(dot(coatN, coatV)) + 1e-5);
coatNdotL = clamp(dot(coatN, coatL), EPSILON_DOT_CLAMP, 1);
coatNdotV = saturate(abs(dot(coatN, coatV)) + EPSILON_DOT_CLAMP);
coatNdotH = saturate(dot(coatN, coatH));
coatVdotH = saturate(dot(coatV, coatH));
}
Expand All @@ -390,8 +390,8 @@ namespace PBR
const float wetnessF0 = 0.02;

float3 H = normalize(V + L);
float NdotL = clamp(dot(N, L), 1e-5, 1);
float NdotV = saturate(abs(dot(N, V)) + 1e-5);
float NdotL = clamp(dot(N, L), EPSILON_DOT_CLAMP, 1);
float NdotV = saturate(abs(dot(N, V)) + EPSILON_DOT_CLAMP);
float NdotH = saturate(dot(N, H));
float VdotH = saturate(dot(V, H));

Expand Down Expand Up @@ -483,7 +483,7 @@ namespace PBR
const float wetnessStrength = 1;
const float wetnessF0 = 0.02;

float NdotV = saturate(abs(dot(N, V)) + 1e-5);
float NdotV = saturate(abs(dot(N, V)) + EPSILON_DOT_CLAMP);
float2 specularBRDF = BRDF::EnvBRDFApproxLazarov(roughness, NdotV);
float3 specularLobeWeight = wetnessF0 * specularBRDF.x + specularBRDF.y;

Expand Down