How to pass Texture2D to compute shader

Development Rendering
, , ,
1

I’m working on a compute shader plugin. It works fine – until I try to add a texture2d shader parameter.

In my shader CPP I declare the paramter blocks like this:

	DECLARE_GLOBAL_SHADER(FComputeShaderExampleCS);
	SHADER_USE_PARAMETER_STRUCT(FComputeShaderExampleCS, FGlobalShader);

	BEGIN_SHADER_PARAMETER_STRUCT(FParameters, )
		SHADER_PARAMETER_UAV(RWTexture2D<uint>, OutputTexture)
		SHADER_PARAMETER(FVector2D, TextureSize) // Metal doesn't support GetDimensions(), so we send in this data via our parameters.
		SHADER_PARAMETER(float, SimulationState)
		SHADER_PARAMETER_TEXTURE(Texture2D, TestTexture)
	END_SHADER_PARAMETER_STRUCT()

and in the corresponding USF file I have this:

RWTexture2D<uint> OutputTexture;
float2 TextureSize;
float SimulationState;
float Dummy;
Texture2D TestTexture;

However when I activate the shader, I get the following check exception:

Assertion failed: Bindings.StructureLayoutHash == ParametersMetadata->GetLayoutHash()

I’m not actually changing the bound texture (at least, not intentionally). Converting SHADER_PARAMETER_TEXTURE(Texture2D, TestTexture) to SHADER_PARAMETER_UAV(Texture2D, TestTexture) avoids the exception but doesn’t work (calling Load() on the texture always returns (0,0,0,0), or perhaps (NAN,NAN,NAN,NAN))

What’s the expected method for passing a Texture2D Parameter to a compute shader?

2

You need to use SetShaderTexture/SetShaderResourceViewParameter/SetUAVParameter RHI commands.

3

It’s generating the error inside the ValidateShaderParameters() that’s called in SetShaderParameters() before it gets to the call to RHICmdList.SetShaderTexture()

Commenting out ValidateShaderParameters() let’s it work as expected… but I don’t like doing that kind of hack. I’d like to understand where the Bindings.StructureLayoutHash → ParametersMetadata->GetLayoutHash delta comes from

4

the SetShaderTexture function takes a FRHITexture as input.
Though i didn’t find anything about how to create a FRHITexture from a UTexture2D.
Do you know if and how this that is possible?