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PBR: Fixed noise in IBL irradiance cube map (close #200)
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@MikhailGorobets @TheMostDiligent
MikhailGorobets authored and TheMostDiligent committed May 15, 2024
1 parent ee0295b commit cb9d389
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Showing 4 changed files with 55 additions and 27 deletions.
27 changes: 17 additions & 10 deletions PBR/src/PBR_Renderer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -527,7 +527,12 @@ void PBR_Renderer::PrecomputeCubemaps(IDeviceContext* pCtx,
float Roughness;
float EnvMapWidth;
float EnvMapHeight;
uint NumSamples;
float EnvMapMipCount;

uint NumSamples;
uint Padding0;
uint Padding1;
uint Padding2;
};

if (!m_PrecomputeEnvMapAttribsCB)
Expand Down Expand Up @@ -687,10 +692,11 @@ void PBR_Renderer::PrecomputeCubemaps(IDeviceContext* pCtx,
VERIFY_EXPR(mip == 0);
{
MapHelper<PrecomputeEnvMapAttribs> Attribs{pCtx, m_PrecomputeEnvMapAttribsCB, MAP_WRITE, MAP_FLAG_DISCARD};
Attribs->Rotation = Matrices[face];
Attribs->EnvMapWidth = static_cast<float>(pEnvironmentMap->GetTexture()->GetDesc().Width);
Attribs->EnvMapHeight = static_cast<float>(pEnvironmentMap->GetTexture()->GetDesc().Height);
Attribs->NumSamples = NumDiffuseSamples;
Attribs->Rotation = Matrices[face];
Attribs->EnvMapWidth = static_cast<float>(pEnvironmentMap->GetTexture()->GetDesc().Width);
Attribs->EnvMapHeight = static_cast<float>(pEnvironmentMap->GetTexture()->GetDesc().Height);
Attribs->EnvMapMipCount = static_cast<float>(pEnvironmentMap->GetTexture()->GetDesc().MipLevels);
Attribs->NumSamples = NumDiffuseSamples;
}
DrawAttribs drawAttrs(4, DRAW_FLAG_VERIFY_ALL);
pCtx->Draw(drawAttrs);
Expand All @@ -706,11 +712,12 @@ void PBR_Renderer::PrecomputeCubemaps(IDeviceContext* pCtx,
ProcessCubemapFaces(pCtx, pPrefilteredEnvMap, [&](ITextureView* pRTV, Uint32 mip, Uint32 face) {
{
MapHelper<PrecomputeEnvMapAttribs> Attribs{pCtx, m_PrecomputeEnvMapAttribsCB, MAP_WRITE, MAP_FLAG_DISCARD};
Attribs->Rotation = Matrices[face];
Attribs->Roughness = static_cast<float>(mip) / static_cast<float>(pPrefilteredEnvMap->GetDesc().MipLevels - 1);
Attribs->EnvMapWidth = static_cast<float>(pEnvironmentMap->GetTexture()->GetDesc().Width);
Attribs->EnvMapHeight = static_cast<float>(pEnvironmentMap->GetTexture()->GetDesc().Height);
Attribs->NumSamples = NumSpecularSamples;
Attribs->Rotation = Matrices[face];
Attribs->Roughness = static_cast<float>(mip) / static_cast<float>(pPrefilteredEnvMap->GetDesc().MipLevels - 1);
Attribs->EnvMapWidth = static_cast<float>(pEnvironmentMap->GetTexture()->GetDesc().Width);
Attribs->EnvMapHeight = static_cast<float>(pEnvironmentMap->GetTexture()->GetDesc().Height);
Attribs->EnvMapMipCount = static_cast<float>(pEnvironmentMap->GetTexture()->GetDesc().MipLevels);
Attribs->NumSamples = NumSpecularSamples;
}

DrawAttribs drawAttrs(4, DRAW_FLAG_VERIFY_ALL);
Expand Down
22 changes: 13 additions & 9 deletions Shaders/PBR/private/ComputeIrradianceMap.psh
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,12 @@ cbuffer FilterAttribs
float g_Roughness;
float g_EnvMapWidth;
float g_EnvMapHeight;
float g_EnvMipCount;

uint g_NumSamples;
uint _Padding0;
uint _Padding1;
uint _Padding2;
}

float3 SampleEnvrionmentMap(float3 R, float MipLevel)
Expand All @@ -47,7 +52,7 @@ float3 IrradianceMap(float3 N)
// Importance sample the hemisphere with a cosine-weighted distribution
float3 L = ImportanceSampleGGX(Xi, 1.0, N);

#if OPTIMIZE_SAMPLES
#if OPTIMIZE_SAMPLES
// NdotL is equal to cos(theta)
float NoL = max(dot(N, L), 0.0);

Expand All @@ -57,18 +62,17 @@ float3 IrradianceMap(float3 N)
// Solid angle of current smple
float OmegaS = 1.0 / (float(g_NumSamples) * pdf);

float NumPixels = g_EnvMapWidth * g_EnvMapHeight;
#if ENV_MAP_TYPE == ENV_MAP_TYPE_CUBE
NumPixels *= 6.0;
#endif

// Solid angle of 1 pixel across all cube faces
float OmegaP = 4.0 * PI / NumPixels;

// Applying mip bias produces better results, especially for environments maps with
float OmegaP = ComputeCubeMapPixelSolidAngle(g_EnvMapWidth, g_EnvMapHeight);
#else
// Solid angle of 1 pixel on sphere
float OmegaP = ComputeSphereMapPixelSolidAngle(g_EnvMapWidth, g_EnvMapHeight, acos(L.y), 0.5);
#endif
// Applying mip bias produces better results, especially for environment maps with
// very bright spots.
float MipBias = 1.0;
float MipLevel = max(0.5 * log2(OmegaS / OmegaP) + MipBias, 0.0);
float MipLevel = clamp(0.5 * log2(OmegaS / max(OmegaP, 1e-10)) + MipBias, 0.0, g_EnvMipCount - 1.0);
#else
float MipLevel = 0.0;
#endif
Expand Down
12 changes: 12 additions & 0 deletions Shaders/PBR/private/PBR_PrecomputeCommon.fxh
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Original file line number Diff line number Diff line change
Expand Up @@ -39,4 +39,16 @@ float3 ImportanceSampleGGX(float2 Xi, float PerceptualRoughness, float3 N)
return TangentX * H.x + TangentY * H.y + N * H.z;
}

float ComputeCubeMapPixelSolidAngle(float Width, float Height)
{
return 4.0 * PI / (6.0 * Width * Height);
}

float ComputeSphereMapPixelSolidAngle(float Width, float Height, float Theta, float Gamma)
{
float dTheta = PI / Width;
float dPhi = 2.0 * PI / Height;
return dPhi * (cos(Theta - 0.5 * dTheta * Gamma) - cos(Theta + 0.5 * dTheta * Gamma));
}

#endif // _PBR_PRECOMPUTE_COMMON_FXH_
21 changes: 13 additions & 8 deletions Shaders/PBR/private/PrefilterEnvMap.psh
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,12 @@ cbuffer FilterAttribs
float g_Roughness;
float g_EnvMapWidth;
float g_EnvMapHeight;
float g_EnvMipCount;

uint g_NumSamples;
uint _Padding0;
uint _Padding1;
uint _Padding2;
}

float3 SampleEnvrionmentMap(float3 R, float MipLevel)
Expand Down Expand Up @@ -71,17 +76,17 @@ float3 PrefilterEnvMap( float PerceptualRoughness, float3 R )
// Solid angle of current smple
float OmegaS = 1.0 / (float(g_NumSamples) * pdf);

float NumPixels = g_EnvMapWidth * g_EnvMapHeight;
#if ENV_MAP_TYPE == ENV_MAP_TYPE_CUBE
NumPixels *= 6.0;
#endif

// Solid angle of 1 pixel across all cube faces
float OmegaP = 4.0 * PI / NumPixels;
// Applying mip bias produces better results, especially for environments maps with
float OmegaP = ComputeCubeMapPixelSolidAngle(g_EnvMapWidth, g_EnvMapHeight);
#else
// Solid angle of 1 pixel on sphere
float OmegaP = ComputeSphereMapPixelSolidAngle(g_EnvMapWidth, g_EnvMapHeight, acos(L.y), 1.0);
#endif
// Applying mip bias produces better results, especially for environment maps with
// very bright spots.
float MipBias = 1.0;
float MipLevel = (AlphaRoughness == 0.0) ? 0.0 : max(0.5 * log2(OmegaS / OmegaP) + MipBias, 0.0);
float MipBias = 1.0;
float MipLevel = (AlphaRoughness == 0.0) ? 0.0 : clamp(0.5 * log2(OmegaS / max(OmegaP, 1e-10)) + MipBias, 0.0, g_EnvMipCount - 1.0);
#else
float MipLevel = 0.0;
#endif
Expand Down

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