How to get the scene Accelerate Structure (TLAS) for custom Ray Tracing

Development Rendering
, ,
5

This works in UE 5.1 & 5.2.

GetWorld()->Scene->GetRenderScene()->RayTracingScene->GetLayerSRVChecked(ERayTracingSceneLayer::Base);

In 5.3, it was replaced with GetLayerView which does not return a FRHIShaderResourceView. Instead, it returns a FRDGBufferSRVRef.

GetWorld()->Scene->GetRenderScene()->RayTracingScene->GetLayerView(ERayTracingSceneLayer::Base);

Does anyone know how to get the TLAS from the FRDGBufferSRVRef without it failing an assert? I tried using GetRHI(), but it fails on an assert:

checkf(DebugData->bAllowRHIAccess || GRDGAllowRHIAccess,
	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);

UPDATE: I was able to get it to work in 5.3. GetRHI() must be called inside the render pass, otherwise it fails the assert.

FRDGBufferSRVRef layerView = GetWorld()->Scene->GetRenderScene()->RayTracingScene->GetLayerView(ERayTracingSceneLayer::Base);

if (layerView)
{
    GraphBuilder->AddPass(...,
        [PassParameters, layerView](FRHIRayTracingCommandList& RHICmdList)
        {
            // Must call GetRHI() inside the render pass like this!
            PassParameters->TLAS = layerView->GetRHI();

            // ..
        }

}
1 Like