184 lines
8.0 KiB
Markdown
184 lines
8.0 KiB
Markdown
---
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title: ToonPostProcess
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date: 2024-05-15 16:50:13
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excerpt:
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tags:
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rating: ⭐
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---
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# FFT
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# Bloom
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Bloom主要分
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- Bloom
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- FFTBloom
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- LensFlares
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BloomThreshold，ClampMin = "-1.0", UIMax = "8.0"。
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相关逻辑位于：
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```c++
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if (bBloomSetupRequiredEnabled)
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{
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const float BloomThreshold = View.FinalPostProcessSettings.BloomThreshold;
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FBloomSetupInputs SetupPassInputs;
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SetupPassInputs.SceneColor = DownsampleInput;
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SetupPassInputs.EyeAdaptationBuffer = EyeAdaptationBuffer;
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SetupPassInputs.EyeAdaptationParameters = &EyeAdaptationParameters;
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SetupPassInputs.LocalExposureParameters = &LocalExposureParameters;
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SetupPassInputs.LocalExposureTexture = CVarBloomApplyLocalExposure.GetValueOnRenderThread() ? LocalExposureTexture : nullptr;
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SetupPassInputs.BlurredLogLuminanceTexture = LocalExposureBlurredLogLumTexture;
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SetupPassInputs.Threshold = BloomThreshold;
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SetupPassInputs.ToonThreshold = View.FinalPostProcessSettings.ToonBloomThreshold;
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DownsampleInput = AddBloomSetupPass(GraphBuilder, View, SetupPassInputs);
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}
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```
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## FFTBloom
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***普通Bloom算法只能做到圆形光斑，对于自定义形状的就需要使用FFTBloom。***
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- FFT Bloom:https://zhuanlan.zhihu.com/p/611582936
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- Unity FFT Bloom:https://github.com/AKGWSB/FFTConvolutionBloom
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### 频域与卷积定理
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图像可以视为二维的信号，而一个信号可以通过 **不同频率** 的 Sine & Cosine 函数的线性叠加来近似得到。对于每个频率的函数，我们乘以一个常数振幅并叠加到最终的结果上，这些振幅叫做 **频谱**。值得注意的是所有的 F_k 都是 **复数**：
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此时频域上的每个振幅不再代表某个单个的时域样本，而是代表该频段的 Sine & Cosine 函数对时域信号的 **整体** 贡献。频域信号包含了输入图像的全部时域信息，***因此卷积定理告诉我们在时域上对信号做卷积，等同于将源图像与滤波盒图像在频域上的频谱（上图系数 V_k）做简单复数 **乘法***：
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一一对位的乘法速度是远远快于需要循环累加的朴素卷积操作。因此接下来我们的目标就是找到一种方法，建立图像信号与其频域之间的联系。在通信领域通常使用傅里叶变换来进行信号的频、时域转换
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### 相关代码
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- c++
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- AddFFTBloomPass()
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- FBloomFinalizeApplyConstantsCS （Bloom计算完成）
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- AddTonemapPass()，PassInputs.Bloom = Bloom与PassInputs.SceneColorApplyParamaters
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- Shader
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-
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**FBloomFindKernelCenterCS**：用于找到Bloom效果的核（Kernel）中心(纹理中找到最亮的像素)。用于在一个，并记录其位置。主要通过计算Luminance来获取到中心区域，而在这里的中心区域可以有多个，这也代表着在最终输出的SceneColor里可以有多个【曝点光晕(Bloom)效果】
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# 实用代码
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代码位于DeferredShadingCommon.ush：
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```c++
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// @param UV - UV space in the GBuffer textures (BufferSize resolution)
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FGBufferData GetGBufferData(float2 UV, bool bGetNormalizedNormal = true)
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{
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#if GBUFFER_REFACTOR
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return DecodeGBufferDataUV(UV,bGetNormalizedNormal);
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#else
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float4 GBufferA = Texture2DSampleLevel(SceneTexturesStruct.GBufferATexture, SceneTexturesStruct_GBufferATextureSampler, UV, 0);
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float4 GBufferB = Texture2DSampleLevel(SceneTexturesStruct.GBufferBTexture, SceneTexturesStruct_GBufferBTextureSampler, UV, 0);
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float4 GBufferC = Texture2DSampleLevel(SceneTexturesStruct.GBufferCTexture, SceneTexturesStruct_GBufferCTextureSampler, UV, 0);
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float4 GBufferD = Texture2DSampleLevel(SceneTexturesStruct.GBufferDTexture, SceneTexturesStruct_GBufferDTextureSampler, UV, 0);
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float CustomNativeDepth = Texture2DSampleLevel(SceneTexturesStruct.CustomDepthTexture, SceneTexturesStruct_CustomDepthTextureSampler, UV, 0).r;
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// BufferToSceneTextureScale is necessary when translucent materials are rendered in a render target
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// that has a different resolution than the scene color textures, e.g. r.SeparateTranslucencyScreenPercentage < 100.
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int2 IntUV = (int2)trunc(UV * View.BufferSizeAndInvSize.xy * View.BufferToSceneTextureScale.xy);
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uint CustomStencil = SceneTexturesStruct.CustomStencilTexture.Load(int3(IntUV, 0)) STENCIL_COMPONENT_SWIZZLE;
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#if ALLOW_STATIC_LIGHTING
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float4 GBufferE = Texture2DSampleLevel(SceneTexturesStruct.GBufferETexture, SceneTexturesStruct_GBufferETextureSampler, UV, 0);
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#else
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float4 GBufferE = 1;
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#endif
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float4 GBufferF = Texture2DSampleLevel(SceneTexturesStruct.GBufferFTexture, SceneTexturesStruct_GBufferFTextureSampler, UV, 0);
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#if WRITES_VELOCITY_TO_GBUFFER
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float4 GBufferVelocity = Texture2DSampleLevel(SceneTexturesStruct.GBufferVelocityTexture, SceneTexturesStruct_GBufferVelocityTextureSampler, UV, 0);
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#else
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float4 GBufferVelocity = 0;
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#endif
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float SceneDepth = CalcSceneDepth(UV);
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return DecodeGBufferData(GBufferA, GBufferB, GBufferC, GBufferD, GBufferE, GBufferF, GBufferVelocity, CustomNativeDepth, CustomStencil, SceneDepth, bGetNormalizedNormal, CheckerFromSceneColorUV(UV));
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#endif
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}
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// Minimal path for just the lighting model, used to branch around unlit pixels (skybox)
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uint GetShadingModelId(float2 UV)
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{
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return DecodeShadingModelId(Texture2DSampleLevel(SceneTexturesStruct.GBufferBTexture, SceneTexturesStruct_GBufferBTextureSampler, UV, 0).a);
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}
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```
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## ShadingModel判断
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```c++
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bool IsToonShadingModel(float2 UV)
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{
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uint ShadingModel = DecodeShadingModelId(Texture2DSampleLevel(SceneTexturesStruct.GBufferBTexture, SceneTexturesStruct_GBufferBTextureSampler, UV, 0).a);
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return ShadingModel == SHADINGMODELID_TOONSTANDARD
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|| ShadingModel == SHADINGMODELID_PREINTEGRATED_SKIN;
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}
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```
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PS.需要Shader添加FSceneTextureShaderParameters/FSceneTextureUniformParameters。
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```c++
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IMPLEMENT_STATIC_UNIFORM_BUFFER_STRUCT(FSceneTextureUniformParameters, "SceneTexturesStruct", SceneTextures);
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BEGIN_SHADER_PARAMETER_STRUCT(FSceneTextureShaderParameters, ENGINE_API)
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SHADER_PARAMETER_RDG_UNIFORM_BUFFER(FSceneTextureUniformParameters, SceneTextures)
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SHADER_PARAMETER_RDG_UNIFORM_BUFFER(FMobileSceneTextureUniformParameters, MobileSceneTextures)
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END_SHADER_PARAMETER_STRUCT()
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```
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# ToneMapping
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- UE4/UE5和ACES工作流程:https://zhuanlan.zhihu.com/p/660965710
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UE4版本的笔记：[[UE4 ToneMapping]]
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TonemapCommon.ush中的FilmToneMap()在CombineLUTsCommon()中调用。其顺序为：
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1. AddCombineLUTPass() => PostProcessCombineLUTs.usf
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2. AddTonemapPass() => PostProcessTonemap.usf
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```c++
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void AddPostProcessingPasses()
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{
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...
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{
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FRDGTextureRef ColorGradingTexture = nullptr;
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if (bPrimaryView)
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{
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ColorGradingTexture = AddCombineLUTPass(GraphBuilder, View);
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}
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// We can re-use the color grading texture from the primary view.
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else if (View.GetTonemappingLUT())
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{
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ColorGradingTexture = TryRegisterExternalTexture(GraphBuilder, View.GetTonemappingLUT());
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}
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else
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{
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const FViewInfo* PrimaryView = static_cast<const FViewInfo*>(View.Family->Views[0]);
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ColorGradingTexture = TryRegisterExternalTexture(GraphBuilder, PrimaryView->GetTonemappingLUT());
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}
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FTonemapInputs PassInputs;
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PassSequence.AcceptOverrideIfLastPass(EPass::Tonemap, PassInputs.OverrideOutput);
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PassInputs.SceneColor = SceneColorSlice;
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PassInputs.Bloom = Bloom;
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PassInputs.SceneColorApplyParamaters = SceneColorApplyParameters;
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PassInputs.LocalExposureTexture = LocalExposureTexture;
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PassInputs.BlurredLogLuminanceTexture = LocalExposureBlurredLogLumTexture;
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PassInputs.LocalExposureParameters = &LocalExposureParameters;
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PassInputs.EyeAdaptationParameters = &EyeAdaptationParameters;
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PassInputs.EyeAdaptationBuffer = EyeAdaptationBuffer;
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PassInputs.ColorGradingTexture = ColorGradingTexture;
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PassInputs.bWriteAlphaChannel = AntiAliasingMethod == AAM_FXAA || bProcessSceneColorAlpha;
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PassInputs.bOutputInHDR = bTonemapOutputInHDR;
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SceneColor = AddTonemapPass(GraphBuilder, View, PassInputs);
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}
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...
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}
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```
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## PostProcessCombineLUTs.usf
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## PostProcessTonemap.usf |