CustomComputeExample

This is an example of how to write custom compute-shaders in Unreal Engine 4.27 (there is also a 4.26 branch) The main goal of this project is to provide an example of how to use the RDG to transfer large amounts of data to the GPU.
The Wiki of this project contains an explaination of the code.

The implementation and usage of the shader lies entirely in the plugin of this project. To demonstrate the use of compute-shaders, the project just colours a texture with the position of the first vertex of a given mesh.

And I have Modified Engine Code For AllowRHIAccess Function

Go to \Engine\Source\Runtime\RenderCore\Public\RenderGraphResources.h

Find The FRDGResource Class Make Following Changes.

 /** Generic graph resource. */
class RENDERCORE_API FRDGResource
{
public:
	FRDGResource(const FRDGResource&) = delete;
	virtual ~FRDGResource() = default;

	// Name of the resource for debugging purpose.
	const TCHAR* const Name = nullptr;

	//////////////////////////////////////////////////////////////////////////
	//! The following methods may only be called during pass execution.

	/** Marks this resource as actually used by a resource. This is to track what dependencies on pass was actually unnecessary. */
#if RDG_ENABLE_DEBUG
	virtual void MarkResourceAsUsed();
#else
	inline  void MarkResourceAsUsed() {}
#endif

	FRHIResource* GetRHI() const
	{
		
		ValidateRHIAccess();
		return ResourceRHI;
	}
	void AllowRHIAccess(bool bAllow)
	{
		DebugData.bAllowRHIAccess = bAllow;
	}
	//////////////////////////////////////////////////////////////////////////

protected:
	FRDGResource(const TCHAR* InName)
		: Name(InName)
	{}

	/** Assigns this resource as a simple passthrough container for an RHI resource. */
	void SetPassthroughRHI(FRHIResource* InResourceRHI)
	{
		ResourceRHI = InResourceRHI;
#if RDG_ENABLE_DEBUG
		DebugData.bAllowRHIAccess = true;
		DebugData.bPassthrough = true;
#endif
	}

	bool IsPassthrough() const
	{
#if RDG_ENABLE_DEBUG
		return DebugData.bPassthrough;
#else
		return false;
#endif
	}

	/** Verify that the RHI resource can be accessed at a pass execution. */
	void ValidateRHIAccess() const
	{
		
#if RDG_ENABLE_DEBUG
		checkf(DebugData.bAllowRHIAccess,
			TEXT("Accessing the RHI resource of %s at this time is not allowed. If you hit this check in pass, ")
			TEXT("that is due to this resource not being referenced in the parameters of your pass."),
			Name);
#endif
	}

	FRHIResource* GetRHIUnchecked() const
	{
		return ResourceRHI;
	}

	FRHIResource* ResourceRHI = nullptr;

private:
#if RDG_ENABLE_DEBUG
	class FDebugData
	{
	private:
		/** Boolean to track at runtime whether a resource is actually used by the lambda of a pass or not, to detect unnecessary resource dependencies on passes. */
		bool bIsActuallyUsedByPass = false;

		/** Boolean to track at pass execution whether the underlying RHI resource is allowed to be accessed. */
		bool bAllowRHIAccess = false;

		/** If true, the resource is not attached to any builder and exists as a dummy container for staging code to RDG. */
		bool bPassthrough = false;

		friend FRDGResource;
		friend FRDGUserValidation;
	} DebugData;
#endif

	friend FRDGBuilder;
	friend FRDGUserValidation;
};