/ue-materials-rendering

Global Shaders and the Render Dependency Graph

For a real HLSL pass, declare a FGlobalShader subclass and drive it with the Render Dependency Graph. Build.cs needs "RenderCore", "RHI" and "Projects".

#include "GlobalShader.h"
#include "ShaderParameterMacros.h"
#include "ShaderParameterStruct.h"

class FMyBlurCS : public FGlobalShader
{
public:
    DECLARE_GLOBAL_SHADER(FMyBlurCS);
    SHADER_USE_PARAMETER_STRUCT(FMyBlurCS, FGlobalShader);

    BEGIN_SHADER_PARAMETER_STRUCT(FParameters, )
        SHADER_PARAMETER(float, Radius)
        SHADER_PARAMETER_RDG_TEXTURE(Texture2D, InputTexture)
        SHADER_PARAMETER_RDG_TEXTURE_UAV(RWTexture2D<float4>, OutputTexture)
    END_SHADER_PARAMETER_STRUCT()
};

IMPLEMENT_GLOBAL_SHADER(FMyBlurCS, "/MyGame/MyBlur.usf", "MainCS", SF_Compute);

Passes are added to an FRDGBuilder with GraphBuilder.AddPass(RDG_EVENT_NAME("MyBlur"), Parameters, ERDGPassFlags::Compute, [](FRHICommandList& RHICmdList) { ... }) and submitted with GraphBuilder.Execute(). Shader maps come from GetGlobalShaderMap(EShaderPlatform Platform).

The /MyGame/ virtual path must be registered before shaders compile — do it in the module's StartupModule, and give that module "LoadingPhase": "PostConfigInit" in the .uplugin/.uproject; a global shader type registered later hits the "Shader type was loaded too late" checkf (Shader.cpp:315). The usual Default phase is too late:

#include "Interfaces/IPluginManager.h"   // "Projects" module
#include "ShaderCore.h"                  // RenderCore; AddShaderSourceDirectoryMapping(const FString& VirtualShaderDirectory, const FString& RealShaderDirectory)

void FMyGameModule::StartupModule()
{
    const FString ShaderDir = FPaths::Combine(
        IPluginManager::Get().FindPlugin(TEXT("MyGame"))->GetBaseDir(), TEXT("Shaders"));   // plugin module; for a game module use FPaths::ProjectDir()
    AddShaderSourceDirectoryMapping(TEXT("/MyGame"), ShaderDir);
}