291 lines
12 KiB
Markdown
291 lines
12 KiB
Markdown
---
|
||
title: ToonReflection
|
||
date: 2025-03-20 17:04:16
|
||
excerpt:
|
||
tags:
|
||
rating: ⭐
|
||
---
|
||
# 反射功能相关Pass
|
||
- ReflectionIndirect(None)
|
||
- [[#ReflectionEnvironmentAndSky]]
|
||
- DiffuseIndirectAndAO(Lumen/SSR)
|
||
- LumenReflections
|
||
- [[#DiffuseIndirectComposite]]
|
||
|
||
## ReflectionEnvironmentAndSky
|
||
位于IndirectLightRendering.cpp的RenderDeferredReflectionsAndSkyLighting() => `AddSkyReflectionPass()`
|
||
|
||
当`DiffuseIndirectMethod = EDiffuseIndirectMethod::Lumen`（也就是开启Lumen GI），如果反射方法为Lumen或者SSR则不会执行后续逻辑。
|
||
|
||
不开启Lumen GI，反射方法为：
|
||
- Lumen：`RenderLumenReflections()`
|
||
- Rtx Reflection：`RenderRayTracingReflections()`
|
||
- SSR：`ScreenSpaceRayTracing::RenderScreenSpaceReflections()`
|
||
|
||
`RenderDeferredReflectionsAndSkyLighting()`主要执行了：
|
||
1. SkyLightDiffuse
|
||
1. RenderDistanceFieldLighting()
|
||
1. RenderDistanceFieldAOScreenGrid()：渲染距离场AO。
|
||
2. RenderCapsuleShadowsForMovableSkylight()：渲染胶囊阴影。
|
||
2. ReflectionIndirect
|
||
- RenderLumenReflections()
|
||
- RenderRayTracingReflections()
|
||
- RenderScreenSpaceReflections()
|
||
3. Denoise
|
||
- Denoiser：IScreenSpaceDenoiser::DenoiseReflections()
|
||
- TemporalFilter：AddTemporalAAPass()
|
||
4. RenderDeferredPlanarReflections()：合成平面反射结果。
|
||
5. AddSkyReflectionPass()
|
||
|
||
几种反射方式的大致执行逻辑：
|
||
- LumenReflection
|
||
1. 输出FRDGTextureRef ReflectionsColor。
|
||
- SSR与Rtx
|
||
1. 输出结果到IScreenSpaceDenoiser::FReflectionsInputs DenoiserInputs的FRDGTextureRef Color。
|
||
2. 执行对应的降噪算法。
|
||
3. 结果赋予给FRDGTextureRef ReflectionsColor。
|
||
- 执行完上述反射方法后，最后执行`AddSkyReflectionPass()`
|
||
|
||
FReflectionEnvironmentSkyLightingPS位于/Engine/Private/ReflectionEnvironmentPixelShader.usf的`ReflectionEnvironmentSkyLighting()`。
|
||
|
||
### ReflectionEnvironmentSkyLighting
|
||
```c++
|
||
void ReflectionEnvironmentSkyLighting(
|
||
in float4 SvPosition : SV_Position,
|
||
out float4 OutColor : SV_Target0
|
||
#if STRATA_OPAQUE_ROUGH_REFRACTION_ENABLED
|
||
, out float3 OutOpaqueRoughRefractionSceneColor : SV_Target1
|
||
, out float3 OutSubSurfaceSceneColor : SV_Target2
|
||
#endif
|
||
)
|
||
{
|
||
ResolvedView = ResolveView();
|
||
//计算获去BufferUV、ScreenPosition
|
||
uint2 PixelPos = SvPosition.xy;
|
||
float2 BufferUV = SvPositionToBufferUV(SvPosition);
|
||
float2 ScreenPosition = SvPositionToScreenPosition(SvPosition).xy;
|
||
|
||
OutColor = 0.0f;
|
||
#if STRATA_OPAQUE_ROUGH_REFRACTION_ENABLED
|
||
OutOpaqueRoughRefractionSceneColor = 0.0f;
|
||
OutSubSurfaceSceneColor = 0.0f;
|
||
#endif
|
||
|
||
#if STRATA_ENABLED
|
||
...
|
||
...
|
||
#else // STRATA_ENABLED
|
||
|
||
// Sample scene textures.
|
||
FGBufferData GBuffer = GetGBufferDataFromSceneTextures(BufferUV);
|
||
|
||
uint ShadingModelID = GBuffer.ShadingModelID;
|
||
const bool bUnlitMaterial = ShadingModelID == SHADINGMODELID_UNLIT;
|
||
|
||
float3 DiffuseColor = GBuffer.DiffuseColor;
|
||
float3 SpecularColor = GBuffer.SpecularColor;
|
||
RemapClearCoatDiffuseAndSpecularColor(GBuffer, ScreenPosition, DiffuseColor, SpecularColor);//针对清漆材质进行Diffuse颜色与Specular颜色重新映射
|
||
|
||
// Sample the ambient occlusion that is dynamically generated every frame.
|
||
float AmbientOcclusion = AmbientOcclusionTexture.SampleLevel(AmbientOcclusionSampler, BufferUV, 0).r;
|
||
|
||
float3 BentNormal = GBuffer.WorldNormal;
|
||
#if APPLY_SKY_SHADOWING
|
||
{
|
||
BentNormal = UpsampleDFAO(BufferUV, GBuffer.Depth, GBuffer.WorldNormal);
|
||
}
|
||
#endif
|
||
|
||
#if ENABLE_DYNAMIC_SKY_LIGHT
|
||
BRANCH
|
||
if (!bUnlitMaterial) // Only light pixels marked as lit //Unlit材质不会计算动态天光GI的效果。
|
||
{
|
||
float3 TranslatedWorldPosition = mul(float4(GetScreenPositionForProjectionType(ScreenPosition, GBuffer.Depth), GBuffer.Depth, 1), View.ScreenToTranslatedWorld).xyz;
|
||
const float CloudVolumetricAOShadow = GetCloudVolumetricAOShadow(TranslatedWorldPosition);//从体积云 VolumetricCloudShadowMapTexture中取得ShadowFrontDepthKm、MaxOpticalDepth，MeanExtinction，最终计算出体积云阴影。UE5.3该函数没有启用。
|
||
|
||
float3 SkyLighting = CloudVolumetricAOShadow * SkyLightDiffuse(GBuffer, AmbientOcclusion, BufferUV, ScreenPosition, BentNormal, DiffuseColor);
|
||
|
||
FLightAccumulator LightAccumulator = (FLightAccumulator)0;
|
||
const bool bNeedsSeparateSubsurfaceLightAccumulation = UseSubsurfaceProfile(ShadingModelID);
|
||
LightAccumulator_Add(LightAccumulator, SkyLighting, SkyLighting, 1.0f, bNeedsSeparateSubsurfaceLightAccumulation);
|
||
OutColor = LightAccumulator_GetResult(LightAccumulator);
|
||
}
|
||
|
||
#endif // ENABLE_DYNAMIC_SKY_LIGHT
|
||
|
||
BRANCH
|
||
if (!bUnlitMaterial && ShadingModelID != SHADINGMODELID_HAIR)//
|
||
{
|
||
OutColor.xyz += ReflectionEnvironment(GBuffer, AmbientOcclusion, BufferUV, ScreenPosition, SvPosition, BentNormal, SpecularColor, ShadingModelID);
|
||
}
|
||
|
||
#endif // STRATA_ENABLED
|
||
}
|
||
|
||
|
||
```
|
||
|
||
### SkyLightDiffuse
|
||
1. 计算float3 SkyLightingNormal、FSkyLightVisibilityData SkyVisData。
|
||
2. 计算Normal、ViewVector、NoV。
|
||
3. 针对制定ShadingModel进行额外计算：
|
||
1. SHADINGMODELID_TWOSIDED_FOLIAGE：使用Normal反向量取得SkySHDiffuse，在乘以SubsurfaceColor、SkyVisData.SkyDiffuseLookUpMul后累加到结果上。
|
||
2. SHADINGMODELID_SUBSURFACE、SHADINGMODELID_PREINTEGRATED_SKIN：从GBuffer中提取SubsurfaceColor并累加到结果上。
|
||
3. SHADINGMODELID_CLOTH：从GBuffer中提取ClothFuzz(SubsurfaceColor)乘以CustomData.a，并累加到结果上。
|
||
4. SHADINGMODELID_HAIR：
|
||
1. DiffuseColor = EvaluateEnvHair(GBuffer, V, N, L);
|
||
2. SkyVisData.SkyDiffuseLookUpNormal = L;
|
||
3. DiffuseWeight = 1.0f;
|
||
4. 调用GetSkySHDiffuse()计算天光光照效果。GetSkySHDiffuse()本质是采样球谐贴图，来获得天光GI结果。
|
||
|
||
### ReflectionEnvironment
|
||
```c++
|
||
float3 ReflectionEnvironment(FGBufferData GBuffer, float AmbientOcclusion, float2 BufferUV, float2 ScreenPosition, float4 SvPosition, float3 BentNormal, float3 SpecularColor, uint ShadingModelID)
|
||
{
|
||
float4 Color = float4(0, 0, 0, 1);
|
||
|
||
float IndirectIrradiance = GBuffer.IndirectIrradiance;
|
||
|
||
#if ENABLE_SKY_LIGHT && ALLOW_STATIC_LIGHTING
|
||
BRANCH
|
||
// Add in diffuse contribution from dynamic skylights so reflection captures will have something to mix with
|
||
if (ReflectionStruct.SkyLightParameters.y > 0 && ReflectionStruct.SkyLightParameters.z > 0)
|
||
{
|
||
//如果开启天光、并且开启静态关照。会在这里采样SkySH，以此累加间接照明。
|
||
IndirectIrradiance += GetDynamicSkyIndirectIrradiance(BentNormal, GBuffer.WorldNormal);
|
||
}
|
||
#endif
|
||
|
||
//计算反射Vector、WorldNormal、ViewVector
|
||
float3 TranslatedWorldPosition = mul(float4(GetScreenPositionForProjectionType(ScreenPosition, GBuffer.Depth), GBuffer.Depth, 1), View.ScreenToTranslatedWorld).xyz;
|
||
float3 CameraToPixel = normalize(TranslatedWorldPosition - View.TranslatedWorldCameraOrigin);
|
||
float3 ReflectionVector = reflect(CameraToPixel, GBuffer.WorldNormal);
|
||
float3 V = -CameraToPixel;
|
||
float3 N = GBuffer.WorldNormal;
|
||
|
||
const float3 SavedTopLayerNormal = N;
|
||
|
||
#if SUPPORTS_ANISOTROPIC_MATERIALS
|
||
ModifyGGXAnisotropicNormalRoughness(GBuffer.WorldTangent, GBuffer.Anisotropy, GBuffer.Roughness, N, V);
|
||
#endif
|
||
|
||
float3 R = 2 * dot( V, N ) * N - V;
|
||
float NoV = saturate( dot( N, V ) );
|
||
|
||
// Point lobe in off-specular peak direction
|
||
R = GetOffSpecularPeakReflectionDir(N, R, GBuffer.Roughness);
|
||
|
||
// 采样 SSR, planar reflections, RT reflections or Lumen 反射结果。
|
||
float4 ReflectionInput = Texture2DSample(ReflectionTexture, ReflectionTextureSampler, BufferUV);
|
||
Color = CompositeReflections(ReflectionInput, BufferUV, GBuffer.Roughness, ShadingModelID);//Color = float4(ReflectionInput.rgb, 1 - ReflectionInput.a)
|
||
|
||
#if RAY_TRACED_REFLECTIONS
|
||
float4 SavedColor = Color; // When a clear coat material is encountered, we save the reflection buffer color for it to not be affected by operations.
|
||
#endif
|
||
if(GBuffer.ShadingModelID == SHADINGMODELID_CLEAR_COAT )
|
||
{
|
||
#if RAY_TRACED_REFLECTIONS
|
||
Color = float4(0, 0, 0, 1); // Clear coat reflection is expected to be computed on a black background
|
||
#endif
|
||
const float ClearCoat = GBuffer.CustomData.x;
|
||
Color = lerp( Color, float4(0,0,0,1), ClearCoat );
|
||
|
||
#if CLEAR_COAT_BOTTOM_NORMAL
|
||
const float2 oct1 = ((float2(GBuffer.CustomData.a, GBuffer.CustomData.z) * 4) - (512.0/255.0)) + UnitVectorToOctahedron(GBuffer.WorldNormal);
|
||
const float3 ClearCoatUnderNormal = OctahedronToUnitVector(oct1);
|
||
|
||
const float3 BottomEffectiveNormal = ClearCoatUnderNormal;
|
||
R = 2 * dot( V, ClearCoatUnderNormal ) * ClearCoatUnderNormal - V;
|
||
#endif
|
||
}
|
||
|
||
float AO = GBuffer.GBufferAO * AmbientOcclusion;//AmbientOcclusion为SSAO或者RTAO或者DFAO或者Lumen……
|
||
float RoughnessSq = GBuffer.Roughness * GBuffer.Roughness;
|
||
float SpecularOcclusion = GetSpecularOcclusion(NoV, RoughnessSq, AO);
|
||
Color.a *= SpecularOcclusion;
|
||
|
||
#if FEATURE_LEVEL >= FEATURE_LEVEL_SM5
|
||
float2 LocalPosition = SvPosition.xy - View.ViewRectMin.xy;
|
||
|
||
uint GridIndex = ComputeLightGridCellIndex(uint2(LocalPosition.x, LocalPosition.y), GBuffer.Depth);
|
||
uint NumCulledEntryIndex = (ForwardLightData.NumGridCells + GridIndex) * NUM_CULLED_LIGHTS_GRID_STRIDE;
|
||
uint NumCulledReflectionCaptures = min(ForwardLightData.NumCulledLightsGrid[NumCulledEntryIndex + 0], ForwardLightData.NumReflectionCaptures);
|
||
uint DataStartIndex = ForwardLightData.NumCulledLightsGrid[NumCulledEntryIndex + 1];
|
||
#else
|
||
uint DataStartIndex = 0;
|
||
uint NumCulledReflectionCaptures = 0;
|
||
#endif
|
||
|
||
const FBxDFEnergyTerms EnergyTerms = ComputeGGXSpecEnergyTerms(GBuffer.Roughness, NoV, GBuffer.SpecularColor);
|
||
|
||
//常规反射 或 底层清漆 光照计算
|
||
//Top of regular reflection or bottom layer of clear coat.
|
||
Color.rgb += View.PreExposure * GatherRadiance(Color.a, TranslatedWorldPosition, R, GBuffer.Roughness, BentNormal, IndirectIrradiance, GBuffer.ShadingModelID, NumCulledReflectionCaptures, DataStartIndex);
|
||
|
||
BRANCH
|
||
if( GBuffer.ShadingModelID == SHADINGMODELID_CLEAR_COAT)
|
||
{
|
||
const float ClearCoat = GBuffer.CustomData.x;
|
||
const float ClearCoatRoughness = GBuffer.CustomData.y;
|
||
|
||
// Restore saved values needed for the top layer.
|
||
GBuffer.WorldNormal = SavedTopLayerNormal;
|
||
// Recompute some values unaffected by anistropy for the top layer
|
||
N = GBuffer.WorldNormal;
|
||
R = 2 * dot(V, N) * N - V;
|
||
NoV = saturate(dot(N, V));
|
||
R = GetOffSpecularPeakReflectionDir(N, R, ClearCoatRoughness);
|
||
|
||
// TODO EnvBRDF should have a mask param
|
||
#if USE_ENERGY_CONSERVATION
|
||
Color.rgb *= EnergyTerms.E * (1 - ClearCoat);
|
||
#else
|
||
// Hack: Ensures when clear coat is >0, grazing angle does not get too much energy,
|
||
// but preserve response at normal incidence
|
||
float2 AB = PreIntegratedGF.SampleLevel(PreIntegratedGFSampler, float2(NoV, GBuffer.Roughness), 0).rg;
|
||
Color.rgb *= SpecularColor * AB.x + AB.y * saturate(50 * SpecularColor.g) * (1 - ClearCoat);
|
||
#endif
|
||
|
||
// F_Schlick
|
||
const float CoatF0 = 0.04f;
|
||
#if USE_ENERGY_CONSERVATION
|
||
float F = ComputeGGXSpecEnergyTerms(ClearCoatRoughness, NoV, CoatF0).E.x;
|
||
#else
|
||
float F = EnvBRDF(CoatF0, ClearCoatRoughness, NoV).x;
|
||
#endif
|
||
|
||
F *= ClearCoat;
|
||
|
||
float LayerAttenuation = (1 - F);
|
||
Color.rgb *= LayerAttenuation;
|
||
Color.a = F;
|
||
|
||
#if !RAY_TRACED_REFLECTIONS
|
||
Color.rgb += ReflectionInput.rgb * F;
|
||
Color.a *= 1 - ReflectionInput.a;
|
||
#endif
|
||
|
||
Color.a *= SpecularOcclusion;
|
||
|
||
float3 TopLayerR = 2 * dot( V, N ) * N - V;
|
||
Color.rgb += View.PreExposure * GatherRadiance(Color.a, TranslatedWorldPosition, TopLayerR, ClearCoatRoughness, BentNormal, IndirectIrradiance, GBuffer.ShadingModelID, NumCulledReflectionCaptures, DataStartIndex);
|
||
|
||
#if RAY_TRACED_REFLECTIONS
|
||
Color.rgb = SavedColor.rgb + Color.rgb * SavedColor.a; // Compose default clear coat reflection over regular refelction (using Premultiplied alpha where SaveColor.a=transmittance)
|
||
#endif
|
||
}
|
||
else
|
||
{
|
||
#if USE_ENERGY_CONSERVATION
|
||
Color.rgb *= EnergyTerms.E;
|
||
#else
|
||
Color.rgb *= EnvBRDF( SpecularColor, GBuffer.Roughness, NoV );
|
||
#endif
|
||
}
|
||
|
||
// Transform NaNs to black, transform negative colors to black.
|
||
return -min(-Color.rgb, 0.0);
|
||
}
|
||
```
|
||
## DiffuseIndirectComposite
|
||
位于IndirectLightRendering.cpp的`RenderDiffuseIndirectAndAmbientOcclusion()` |