295 lines
12 KiB
Markdown
295 lines
12 KiB
Markdown
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## 前言
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在插件中使用RDG调用ComputeShader的方法，我花了没几天就搞定了。但PixelShader相对来说就麻烦了，怎么搞都没有绘制到RT上。最后还是通过改写DrawFullscreenPixelShader的代码搞定了。
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另外说一下PixelShader的调用和传统的GlobalShader调用很相似。
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## 设置Shader虚拟目录
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这个之前忘记说了，所以这里补充一下，具体操作为在插件的模块启动函数中添加以下代码：：
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```
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void FBRPluginsModule::StartupModule()
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{
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FString PluginShaderDir = FPaths::Combine(IPluginManager::Get().FindPlugin(TEXT("BRPlugins"))->GetBaseDir(), TEXT("Shaders"));
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AddShaderSourceDirectoryMapping(TEXT("/BRPlugins"), PluginShaderDir);
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}
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```
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之后就可以使用这个虚拟目录来定义Shader：
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```
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IMPLEMENT_GLOBAL_SHADER(FSimpleRDGComputeShader, "/BRPlugins/Private/SimpleComputeShader.usf", "MainCS", SF_Compute);
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```
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## 参考案例
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这里我没什么管理可以推荐的，感觉都不是很好。但你可以搜索ERDGPassFlags::Raster就可以找到RDG调用PixelShader的代码。
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## 使用DrawFullscreenPixelShader绘制
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在RDG中已经封装了一个绘制函数DrawFullscreenPixelShader()，可以拿来做测试。使用的方法也比较简单，直接在GraphBuilder.AddPass的Lambda中调用DrawFullscreenPixelShader即可。但
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其使用的顶点格式是公共资源(CommonRenderResources.h)中的GFilterVertexDeclaration.VertexDeclarationRHI、GScreenRectangleVertexBuffer.VertexBufferRHI、GScreenRectangleIndexBuffer.IndexBufferRHI。
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```
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void FScreenRectangleVertexBuffer::InitRHI()
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{
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TResourceArray<FFilterVertex, VERTEXBUFFER_ALIGNMENT> Vertices;
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Vertices.SetNumUninitialized(6);
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Vertices[0].Position = FVector4(1, 1, 0, 1);
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Vertices[0].UV = FVector2D(1, 1);
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Vertices[1].Position = FVector4(0, 1, 0, 1);
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Vertices[1].UV = FVector2D(0, 1);
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Vertices[2].Position = FVector4(1, 0, 0, 1);
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Vertices[2].UV = FVector2D(1, 0);
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Vertices[3].Position = FVector4(0, 0, 0, 1);
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Vertices[3].UV = FVector2D(0, 0);
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//The final two vertices are used for the triangle optimization (a single triangle spans the entire viewport )
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Vertices[4].Position = FVector4(-1, 1, 0, 1);
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Vertices[4].UV = FVector2D(-1, 1);
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Vertices[5].Position = FVector4(1, -1, 0, 1);
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Vertices[5].UV = FVector2D(1, -1);
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// Create vertex buffer. Fill buffer with initial data upon creation
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FRHIResourceCreateInfo CreateInfo(&Vertices);
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VertexBufferRHI = RHICreateVertexBuffer(Vertices.GetResourceDataSize(), BUF_Static, CreateInfo);
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}
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```
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DrawFullscreenPixelShader()使用的VertexShader是FScreenVertexShaderVS，usf为FullscreenVertexShader.usf。代码如下：
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```
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#include "../Common.ush"
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void MainVS(
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float2 InPosition : ATTRIBUTE0,
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float2 InUV : ATTRIBUTE1, // TODO: kill
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out float4 Position : SV_POSITION)
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{
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Position = float4(InPosition.x * 2.0 - 1.0, 1.0 - 2.0 * InPosition.y, 0, 1);
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}
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```
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这里可以看得出一个问题，那就是PixelShader无法获得UV坐标。所以DrawFullscreenPixelShader()能做事情很有限。因此本人写的例子是自定义了顶点格式。
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## CommonRenderResources
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Ue4的已经帮我们设置好了几个基础的VertexDeclaration，位于RenderCore\Public\CommonRenderResources.h。
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GEmptyVertexDeclaration.VertexDeclarationRHI，在Shader中的Input为：
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```
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in uint InstanceId : SV_InstanceID,
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in uint VertexId : SV_VertexID,
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```
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GFilterVertexDeclaration.VertexDeclarationRHI，在Shader中的Input为：
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```
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in float4 InPosition : ATTRIBUTE0,
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in float2 InUV : ATTRIBUTE1,
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```
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对应的顶点缓存与索引缓存为TGlobalResource<FScreenRectangleVertexBuffer> GScreenRectangleVertexBuffer与TGlobalResource<FScreenRectangleIndexBuffer> GScreenRectangleIndexBuffer;
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如果你想在调用PixelShader时使用FScreenRectangleVertexBuffer，就需要转换UV坐标了，(-1,1)=>(0,1)，因为FScreenRectangleVertexBuffer的UV定义范围为(-1,1)。
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## RenderTarget的传入与绑定
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传入的RenderTarget皆可以用Texture2D类型声明。例如：
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```
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BEGIN_SHADER_PARAMETER_STRUCT(FParameters, )
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SHADER_PARAMETER_STRUCT_REF(FSimpleUniformStructParameters, SimpleUniformStruct)
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SHADER_PARAMETER_TEXTURE(Texture2D, TextureVal)
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SHADER_PARAMETER_SAMPLER(SamplerState, TextureSampler)
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SHADER_PARAMETER(FVector4, SimpleColor)
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RENDER_TARGET_BINDING_SLOTS()
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END_SHADER_PARAMETER_STRUCT()
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```
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绑定需要在上面的声明宏中加入RENDER_TARGET_BINDING_SLOTS()，之后设置变量时绑定：
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```
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FSimpleRDGPixelShader::FParameters *Parameters = GraphBuilder.AllocParameters<FSimpleRDGPixelShader::FParameters>();
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Parameters->RenderTargets[0] = FRenderTargetBinding(RDGRenderTarget, ERenderTargetLoadAction::ENoAction);
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```
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还可以绑定DepthStencil
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```
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Parameters->RenderTargets.DepthStencil = FDepthStencilBinding(OutDepthTexture,ERenderTargetLoadAction::ELoad,ERenderTargetLoadAction::ELoad,FExclusiveDepthStencil::DepthNop_StencilWrite);
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```
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在USF中对应Out为：
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```
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out float4 OutColor : SV_Target0,
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out float OutDepth : SV_Depth
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```
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如果有多个RenderTarget绑定，会如SV_Target0、SV_Target1、SV_Target2一般递增。
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## 资源清理
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本人案例中因为只有一个Pass，所以就没有用这两个函数。
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```
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ValidateShaderParameters(PixelShader, Parameters);
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ClearUnusedGraphResources(PixelShader, Parameters);
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```
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## RDGPixelDraw
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直接上代码了。
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```
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void RDGDraw(FRHICommandListImmediate &RHIImmCmdList, FTexture2DRHIRef RenderTargetRHI, FSimpleShaderParameter InParameter, const FLinearColor InColor, FTexture2DRHIRef InTexture)
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{
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check(IsInRenderingThread());
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//Create PooledRenderTarget
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FPooledRenderTargetDesc RenderTargetDesc = FPooledRenderTargetDesc::Create2DDesc(RenderTargetRHI->GetSizeXY(),RenderTargetRHI->GetFormat(), FClearValueBinding::Black, TexCreate_None, TexCreate_RenderTargetable | TexCreate_ShaderResource | TexCreate_UAV, false);
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TRefCountPtr<IPooledRenderTarget> PooledRenderTarget;
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//RDG Begin
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FRDGBuilder GraphBuilder(RHIImmCmdList);
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FRDGTextureRef RDGRenderTarget = GraphBuilder.CreateTexture(RenderTargetDesc, TEXT("RDGRenderTarget"));
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//Setup Parameters
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FSimpleUniformStructParameters StructParameters;
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StructParameters.Color1 = InParameter.Color1;
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StructParameters.Color2 = InParameter.Color2;
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StructParameters.Color3 = InParameter.Color3;
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StructParameters.Color4 = InParameter.Color4;
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StructParameters.ColorIndex = InParameter.ColorIndex;
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FSimpleRDGPixelShader::FParameters *Parameters = GraphBuilder.AllocParameters<FSimpleRDGPixelShader::FParameters>();
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Parameters->TextureVal = InTexture;
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Parameters->TextureSampler = TStaticSamplerState<SF_Trilinear, AM_Clamp, AM_Clamp, AM_Clamp>::GetRHI();
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Parameters->SimpleColor = InColor;
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Parameters->SimpleUniformStruct = TUniformBufferRef<FSimpleUniformStructParameters>::CreateUniformBufferImmediate(StructParameters, UniformBuffer_SingleFrame);
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Parameters->RenderTargets[0] = FRenderTargetBinding(RDGRenderTarget, ERenderTargetLoadAction::ENoAction);
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const ERHIFeatureLevel::Type FeatureLevel = GMaxRHIFeatureLevel; //ERHIFeatureLevel::SM5
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FGlobalShaderMap *GlobalShaderMap = GetGlobalShaderMap(FeatureLevel);
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TShaderMapRef<FSimpleRDGVertexShader> VertexShader(GlobalShaderMap);
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TShaderMapRef<FSimpleRDGPixelShader> PixelShader(GlobalShaderMap);
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//ValidateShaderParameters(PixelShader, Parameters);
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//ClearUnusedGraphResources(PixelShader, Parameters);
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GraphBuilder.AddPass(
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RDG_EVENT_NAME("RDGDraw"),
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Parameters,
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ERDGPassFlags::Raster,
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[Parameters, VertexShader, PixelShader, GlobalShaderMap](FRHICommandList &RHICmdList) {
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FRHITexture2D *RT = Parameters->RenderTargets[0].GetTexture()->GetRHI()->GetTexture2D();
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RHICmdList.SetViewport(0, 0, 0.0f, RT->GetSizeX(), RT->GetSizeY(), 1.0f);
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FGraphicsPipelineStateInitializer GraphicsPSOInit;
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RHICmdList.ApplyCachedRenderTargets(GraphicsPSOInit);
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GraphicsPSOInit.DepthStencilState = TStaticDepthStencilState<false, CF_Always>::GetRHI();
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GraphicsPSOInit.BlendState = TStaticBlendState<>::GetRHI();
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GraphicsPSOInit.RasterizerState = TStaticRasterizerState<>::GetRHI();
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GraphicsPSOInit.PrimitiveType = PT_TriangleList;
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GraphicsPSOInit.BoundShaderState.VertexDeclarationRHI = GTextureVertexDeclaration.VertexDeclarationRHI;
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GraphicsPSOInit.BoundShaderState.VertexShaderRHI = VertexShader.GetVertexShader();
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GraphicsPSOInit.BoundShaderState.PixelShaderRHI = PixelShader.GetPixelShader();
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SetGraphicsPipelineState(RHICmdList, GraphicsPSOInit);
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RHICmdList.SetStencilRef(0);
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SetShaderParameters(RHICmdList, PixelShader, PixelShader.GetPixelShader(), *Parameters);
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RHICmdList.SetStreamSource(0, GRectangleVertexBuffer.VertexBufferRHI, 0);
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RHICmdList.DrawIndexedPrimitive(
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GRectangleIndexBuffer.IndexBufferRHI,
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/*BaseVertexIndex=*/0,
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/*MinIndex=*/0,
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/*NumVertices=*/4,
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/*StartIndex=*/0,
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/*NumPrimitives=*/2,
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/*NumInstances=*/1);
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});
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GraphBuilder.QueueTextureExtraction(RDGRenderTarget, &PooledRenderTarget);
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GraphBuilder.Execute();
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//Copy Result To RenderTarget Asset
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RHIImmCmdList.CopyTexture(PooledRenderTarget->GetRenderTargetItem().ShaderResourceTexture, RenderTargetRHI->GetTexture2D(), FRHICopyTextureInfo());
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}
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```
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调用方法和之前的ComputeShader部分相同，这里就不赘述了。具体的可以参考我的插件。
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### 自定义顶点格式部分
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```
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struct FTextureVertex
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{
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FVector4 Position;
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FVector2D UV;
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};
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class FRectangleVertexBuffer : public FVertexBuffer
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{
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public:
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/** Initialize the RHI for this rendering resource */
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void InitRHI() override
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{
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TResourceArray<FTextureVertex, VERTEXBUFFER_ALIGNMENT> Vertices;
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Vertices.SetNumUninitialized(6);
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Vertices[0].Position = FVector4(1, 1, 0, 1);
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Vertices[0].UV = FVector2D(1, 1);
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Vertices[1].Position = FVector4(-1, 1, 0, 1);
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Vertices[1].UV = FVector2D(0, 1);
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Vertices[2].Position = FVector4(1, -1, 0, 1);
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Vertices[2].UV = FVector2D(1, 0);
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Vertices[3].Position = FVector4(-1, -1, 0, 1);
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Vertices[3].UV = FVector2D(0, 0);
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//The final two vertices are used for the triangle optimization (a single triangle spans the entire viewport )
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Vertices[4].Position = FVector4(-1, 1, 0, 1);
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Vertices[4].UV = FVector2D(-1, 1);
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Vertices[5].Position = FVector4(1, -1, 0, 1);
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Vertices[5].UV = FVector2D(1, -1);
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// Create vertex buffer. Fill buffer with initial data upon creation
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FRHIResourceCreateInfo CreateInfo(&Vertices);
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VertexBufferRHI = RHICreateVertexBuffer(Vertices.GetResourceDataSize(), BUF_Static, CreateInfo);
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}
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};
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class FRectangleIndexBuffer : public FIndexBuffer
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{
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public:
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/** Initialize the RHI for this rendering resource */
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void InitRHI() override
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{
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// Indices 0 - 5 are used for rendering a quad. Indices 6 - 8 are used for triangle optimization.
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const uint16 Indices[] = {0, 1, 2, 2, 1, 3, 0, 4, 5};
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TResourceArray<uint16, INDEXBUFFER_ALIGNMENT> IndexBuffer;
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uint32 NumIndices = UE_ARRAY_COUNT(Indices);
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IndexBuffer.AddUninitialized(NumIndices);
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FMemory::Memcpy(IndexBuffer.GetData(), Indices, NumIndices * sizeof(uint16));
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// Create index buffer. Fill buffer with initial data upon creation
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FRHIResourceCreateInfo CreateInfo(&IndexBuffer);
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IndexBufferRHI = RHICreateIndexBuffer(sizeof(uint16), IndexBuffer.GetResourceDataSize(), BUF_Static, CreateInfo);
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}
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};
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class FTextureVertexDeclaration : public FRenderResource
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{
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public:
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FVertexDeclarationRHIRef VertexDeclarationRHI;
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virtual void InitRHI() override
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{
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FVertexDeclarationElementList Elements;
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uint32 Stride = sizeof(FTextureVertex);
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Elements.Add(FVertexElement(0, STRUCT_OFFSET(FTextureVertex, Position), VET_Float2, 0, Stride));
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Elements.Add(FVertexElement(0, STRUCT_OFFSET(FTextureVertex, UV), VET_Float2, 1, Stride));
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VertexDeclarationRHI = RHICreateVertexDeclaration(Elements);
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}
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virtual void ReleaseRHI() override
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{
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VertexDeclarationRHI.SafeRelease();
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}
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};
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/*
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* Vertex Resource Declaration
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*/
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extern TGlobalResource<FTextureVertexDeclaration> GTextureVertexDeclaration;
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extern TGlobalResource<FRectangleVertexBuffer> GRectangleVertexBuffer;
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extern TGlobalResource<FRectangleIndexBuffer> GRectangleIndexBuffer;
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```
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```
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TGlobalResource<FTextureVertexDeclaration> GTextureVertexDeclaration;
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TGlobalResource<FRectangleVertexBuffer> GRectangleVertexBuffer;
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TGlobalResource<FRectangleIndexBuffer> GRectangleIndexBuffer;
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```
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