(DX12) Read-back buffer for 2D-Texture UAV [closed] - memory-management

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I am trying to read-back ray-traced intersections of a ray's recursive path from the GPU to the CPU in DXR.
I am able to render the intersections into a layered unordered access view Texture2D array, so that each layer of the ray-tree corresponds to one layer in this UAV array.
The problem comes when I try to 'readback' this data from the GPU so the CPU can read it. I have not found a way to copy texture information from the GPU to the CPU - I cannot instantiate a 2D-Texture buffer on the read-back heap. I am now looking into writing this intersection information into a flattened 1D UAV buffer - essentially a g-buffer. However, I am having difficulty initializing this (since each pixel may necessarily contain an intersection, I need a buffer the size of the screen-dimensions*RAY_RECURSION_DEPTH (6 in my case), however the number of elements in a UAV-Buffer is limited to size 345599).
Getting to the point, is there a way for me to read-back from a UAV Texture2D resource? Is there a way for me to create a UAV-Buffer with a larger size than 345599? Or, is there another way I should be going about this altogether?
Thanks.

Answer 1

Readback resources for Direct3D 12 must be buffers (D3D12_RESOURCE_DIMENSION_BUFFER). You create one large enough to hold the Texture2D data (rowpitch * height) and then use CopyTextureRegion to copy it from the GPU to CPU.
D3D12_RESOURCE_DESC bufferDesc = {};
bufferDesc.Alignment = desc.Alignment;
bufferDesc.DepthOrArraySize = 1;
bufferDesc.Dimension = D3D12_RESOURCE_DIMENSION_BUFFER;
bufferDesc.Flags = D3D12_RESOURCE_FLAG_NONE;
bufferDesc.Format = DXGI_FORMAT_UNKNOWN;
bufferDesc.Height = 1;
bufferDesc.Width = srcPitch * desc.Height;
bufferDesc.Layout = D3D12_TEXTURE_LAYOUT_ROW_MAJOR;
bufferDesc.MipLevels = 1;
bufferDesc.SampleDesc.Count = 1;
bufferDesc.SampleDesc.Quality = 0;
See ScreenGrab and Microsoft Docs