12 KiB
12 KiB
前言
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。
另外说一下PixelShader的调用和传统的GlobalShader调用很相似。
设置Shader虚拟目录
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：：
void FBRPluginsModule::StartupModule()
{
FString PluginShaderDir = FPaths::Combine(IPluginManager::Get().FindPlugin(TEXT("BRPlugins"))->GetBaseDir(), TEXT("Shaders"));
AddShaderSourceDirectoryMapping(TEXT("/BRPlugins"), PluginShaderDir);
}
之后就可以使用这个虚拟目录来定义Shader：
IMPLEMENT_GLOBAL_SHADER(FSimpleRDGComputeShader, "/BRPlugins/Private/SimpleComputeShader.usf", "MainCS", SF_Compute);
参考案例
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。
使用DrawFullscreenPixelShader绘制
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
其使用的顶点格式是公共资源(CommonRenderResources.h)中的GFilterVertexDeclaration.VertexDeclarationRHI、GScreenRectangleVertexBuffer.VertexBufferRHI、GScreenRectangleIndexBuffer.IndexBufferRHI。
void FScreenRectangleVertexBuffer::InitRHI()
{
TResourceArray<FFilterVertex, VERTEXBUFFER_ALIGNMENT> Vertices;
Vertices.SetNumUninitialized(6);
Vertices[0].Position = FVector4(1, 1, 0, 1);
Vertices[0].UV = FVector2D(1, 1);
Vertices[1].Position = FVector4(0, 1, 0, 1);
Vertices[1].UV = FVector2D(0, 1);
Vertices[2].Position = FVector4(1, 0, 0, 1);
Vertices[2].UV = FVector2D(1, 0);
Vertices[3].Position = FVector4(0, 0, 0, 1);
Vertices[3].UV = FVector2D(0, 0);
//The final two vertices are used for the triangle optimization (a single triangle spans the entire viewport )
Vertices[4].Position = FVector4(-1, 1, 0, 1);
Vertices[4].UV = FVector2D(-1, 1);
Vertices[5].Position = FVector4(1, -1, 0, 1);
Vertices[5].UV = FVector2D(1, -1);
// Create vertex buffer. Fill buffer with initial data upon creation
FRHIResourceCreateInfo CreateInfo(&Vertices);
VertexBufferRHI = RHICreateVertexBuffer(Vertices.GetResourceDataSize(), BUF_Static, CreateInfo);
}
DrawFullscreenPixelShader()使用的VertexShader是FScreenVertexShaderVS，usf为FullscreenVertexShader.usf。代码如下：
#include "../Common.ush"
void MainVS(
float2 InPosition : ATTRIBUTE0,
float2 InUV : ATTRIBUTE1, // TODO: kill
out float4 Position : SV_POSITION)
{
Position = float4(InPosition.x * 2.0 - 1.0, 1.0 - 2.0 * InPosition.y, 0, 1);
}
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。
CommonRenderResources
Ue4的已经帮我们设置好了几个基础的VertexDeclaration，位于RenderCore\Public\CommonRenderResources.h。
GEmptyVertexDeclaration.VertexDeclarationRHI，在Shader中的Input为：
in uint InstanceId : SV_InstanceID,
in uint VertexId : SV_VertexID,
GFilterVertexDeclaration.VertexDeclarationRHI，在Shader中的Input为：
in float4 InPosition : ATTRIBUTE0,
in float2 InUV : ATTRIBUTE1,
对应的顶点缓存与索引缓存为TGlobalResource GScreenRectangleVertexBuffer与TGlobalResource GScreenRectangleIndexBuffer;
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)。
RenderTarget的传入与绑定
传入的RenderTarget皆可以用Texture2D类型声明。例如：
BEGIN_SHADER_PARAMETER_STRUCT(FParameters, )
SHADER_PARAMETER_STRUCT_REF(FSimpleUniformStructParameters, SimpleUniformStruct)
SHADER_PARAMETER_TEXTURE(Texture2D, TextureVal)
SHADER_PARAMETER_SAMPLER(SamplerState, TextureSampler)
SHADER_PARAMETER(FVector4, SimpleColor)
RENDER_TARGET_BINDING_SLOTS()
END_SHADER_PARAMETER_STRUCT()
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：
FSimpleRDGPixelShader::FParameters *Parameters = GraphBuilder.AllocParameters<FSimpleRDGPixelShader::FParameters>();
Parameters->RenderTargets[0] = FRenderTargetBinding(RDGRenderTarget, ERenderTargetLoadAction::ENoAction);
还可以绑定DepthStencil
Parameters->RenderTargets.DepthStencil = FDepthStencilBinding(OutDepthTexture,ERenderTargetLoadAction::ELoad,ERenderTargetLoadAction::ELoad,FExclusiveDepthStencil::DepthNop_StencilWrite);
在USF中对应Out为：
out float4 OutColor : SV_Target0,
out float OutDepth : SV_Depth
如果有多个RenderTarget绑定，会如SV_Target0、SV_Target1、SV_Target2一般递增。
资源清理
本人案例中因为只有一个Pass，所以就没有用这两个函数。
ValidateShaderParameters(PixelShader, Parameters);
ClearUnusedGraphResources(PixelShader, Parameters);
RDGPixelDraw
直接上代码了。
void RDGDraw(FRHICommandListImmediate &RHIImmCmdList, FTexture2DRHIRef RenderTargetRHI, FSimpleShaderParameter InParameter, const FLinearColor InColor, FTexture2DRHIRef InTexture)
{
check(IsInRenderingThread());
//Create PooledRenderTarget
FPooledRenderTargetDesc RenderTargetDesc = FPooledRenderTargetDesc::Create2DDesc(RenderTargetRHI->GetSizeXY(),RenderTargetRHI->GetFormat(), FClearValueBinding::Black, TexCreate_None, TexCreate_RenderTargetable | TexCreate_ShaderResource | TexCreate_UAV, false);
TRefCountPtr<IPooledRenderTarget> PooledRenderTarget;
//RDG Begin
FRDGBuilder GraphBuilder(RHIImmCmdList);
FRDGTextureRef RDGRenderTarget = GraphBuilder.CreateTexture(RenderTargetDesc, TEXT("RDGRenderTarget"));
//Setup Parameters
FSimpleUniformStructParameters StructParameters;
StructParameters.Color1 = InParameter.Color1;
StructParameters.Color2 = InParameter.Color2;
StructParameters.Color3 = InParameter.Color3;
StructParameters.Color4 = InParameter.Color4;
StructParameters.ColorIndex = InParameter.ColorIndex;
FSimpleRDGPixelShader::FParameters *Parameters = GraphBuilder.AllocParameters<FSimpleRDGPixelShader::FParameters>();
Parameters->TextureVal = InTexture;
Parameters->TextureSampler = TStaticSamplerState<SF_Trilinear, AM_Clamp, AM_Clamp, AM_Clamp>::GetRHI();
Parameters->SimpleColor = InColor;
Parameters->SimpleUniformStruct = TUniformBufferRef<FSimpleUniformStructParameters>::CreateUniformBufferImmediate(StructParameters, UniformBuffer_SingleFrame);
Parameters->RenderTargets[0] = FRenderTargetBinding(RDGRenderTarget, ERenderTargetLoadAction::ENoAction);
const ERHIFeatureLevel::Type FeatureLevel = GMaxRHIFeatureLevel; //ERHIFeatureLevel::SM5
FGlobalShaderMap *GlobalShaderMap = GetGlobalShaderMap(FeatureLevel);
TShaderMapRef<FSimpleRDGVertexShader> VertexShader(GlobalShaderMap);
TShaderMapRef<FSimpleRDGPixelShader> PixelShader(GlobalShaderMap);
//ValidateShaderParameters(PixelShader, Parameters);
//ClearUnusedGraphResources(PixelShader, Parameters);
GraphBuilder.AddPass(
RDG_EVENT_NAME("RDGDraw"),
Parameters,
ERDGPassFlags::Raster,
[Parameters, VertexShader, PixelShader, GlobalShaderMap](FRHICommandList &RHICmdList) {
FRHITexture2D *RT = Parameters->RenderTargets[0].GetTexture()->GetRHI()->GetTexture2D();
RHICmdList.SetViewport(0, 0, 0.0f, RT->GetSizeX(), RT->GetSizeY(), 1.0f);
FGraphicsPipelineStateInitializer GraphicsPSOInit;
RHICmdList.ApplyCachedRenderTargets(GraphicsPSOInit);
GraphicsPSOInit.DepthStencilState = TStaticDepthStencilState<false, CF_Always>::GetRHI();
GraphicsPSOInit.BlendState = TStaticBlendState<>::GetRHI();
GraphicsPSOInit.RasterizerState = TStaticRasterizerState<>::GetRHI();
GraphicsPSOInit.PrimitiveType = PT_TriangleList;
GraphicsPSOInit.BoundShaderState.VertexDeclarationRHI = GTextureVertexDeclaration.VertexDeclarationRHI;
GraphicsPSOInit.BoundShaderState.VertexShaderRHI = VertexShader.GetVertexShader();
GraphicsPSOInit.BoundShaderState.PixelShaderRHI = PixelShader.GetPixelShader();
SetGraphicsPipelineState(RHICmdList, GraphicsPSOInit);
RHICmdList.SetStencilRef(0);
SetShaderParameters(RHICmdList, PixelShader, PixelShader.GetPixelShader(), *Parameters);
RHICmdList.SetStreamSource(0, GRectangleVertexBuffer.VertexBufferRHI, 0);
RHICmdList.DrawIndexedPrimitive(
GRectangleIndexBuffer.IndexBufferRHI,
/*BaseVertexIndex=*/0,
/*MinIndex=*/0,
/*NumVertices=*/4,
/*StartIndex=*/0,
/*NumPrimitives=*/2,
/*NumInstances=*/1);
});
GraphBuilder.QueueTextureExtraction(RDGRenderTarget, &PooledRenderTarget);
GraphBuilder.Execute();
//Copy Result To RenderTarget Asset
RHIImmCmdList.CopyTexture(PooledRenderTarget->GetRenderTargetItem().ShaderResourceTexture, RenderTargetRHI->GetTexture2D(), FRHICopyTextureInfo());
}
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。
自定义顶点格式部分
struct FTextureVertex
{
FVector4 Position;
FVector2D UV;
};
class FRectangleVertexBuffer : public FVertexBuffer
{
public:
/** Initialize the RHI for this rendering resource */
void InitRHI() override
{
TResourceArray<FTextureVertex, VERTEXBUFFER_ALIGNMENT> Vertices;
Vertices.SetNumUninitialized(6);
Vertices[0].Position = FVector4(1, 1, 0, 1);
Vertices[0].UV = FVector2D(1, 1);
Vertices[1].Position = FVector4(-1, 1, 0, 1);
Vertices[1].UV = FVector2D(0, 1);
Vertices[2].Position = FVector4(1, -1, 0, 1);
Vertices[2].UV = FVector2D(1, 0);
Vertices[3].Position = FVector4(-1, -1, 0, 1);
Vertices[3].UV = FVector2D(0, 0);
//The final two vertices are used for the triangle optimization (a single triangle spans the entire viewport )
Vertices[4].Position = FVector4(-1, 1, 0, 1);
Vertices[4].UV = FVector2D(-1, 1);
Vertices[5].Position = FVector4(1, -1, 0, 1);
Vertices[5].UV = FVector2D(1, -1);
// Create vertex buffer. Fill buffer with initial data upon creation
FRHIResourceCreateInfo CreateInfo(&Vertices);
VertexBufferRHI = RHICreateVertexBuffer(Vertices.GetResourceDataSize(), BUF_Static, CreateInfo);
}
};
class FRectangleIndexBuffer : public FIndexBuffer
{
public:
/** Initialize the RHI for this rendering resource */
void InitRHI() override
{
// Indices 0 - 5 are used for rendering a quad. Indices 6 - 8 are used for triangle optimization.
const uint16 Indices[] = {0, 1, 2, 2, 1, 3, 0, 4, 5};
TResourceArray<uint16, INDEXBUFFER_ALIGNMENT> IndexBuffer;
uint32 NumIndices = UE_ARRAY_COUNT(Indices);
IndexBuffer.AddUninitialized(NumIndices);
FMemory::Memcpy(IndexBuffer.GetData(), Indices, NumIndices * sizeof(uint16));
// Create index buffer. Fill buffer with initial data upon creation
FRHIResourceCreateInfo CreateInfo(&IndexBuffer);
IndexBufferRHI = RHICreateIndexBuffer(sizeof(uint16), IndexBuffer.GetResourceDataSize(), BUF_Static, CreateInfo);
}
};
class FTextureVertexDeclaration : public FRenderResource
{
public:
FVertexDeclarationRHIRef VertexDeclarationRHI;
virtual void InitRHI() override
{
FVertexDeclarationElementList Elements;
uint32 Stride = sizeof(FTextureVertex);
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FTextureVertex, Position), VET_Float2, 0, Stride));
Elements.Add(FVertexElement(0, STRUCT_OFFSET(FTextureVertex, UV), VET_Float2, 1, Stride));
VertexDeclarationRHI = RHICreateVertexDeclaration(Elements);
}
virtual void ReleaseRHI() override
{
VertexDeclarationRHI.SafeRelease();
}
};
/*
* Vertex Resource Declaration
*/
extern TGlobalResource<FTextureVertexDeclaration> GTextureVertexDeclaration;
extern TGlobalResource<FRectangleVertexBuffer> GRectangleVertexBuffer;
extern TGlobalResource<FRectangleIndexBuffer> GRectangleIndexBuffer;
TGlobalResource<FTextureVertexDeclaration> GTextureVertexDeclaration;
TGlobalResource<FRectangleVertexBuffer> GRectangleVertexBuffer;
TGlobalResource<FRectangleIndexBuffer> GRectangleIndexBuffer;