Why small texture alignment only allowed for texture2d?

[thakral-shubham]

The documentation (https://learn.microsoft.com/en-us/windows/win32/api/d3d12/ns-d3d12-d3d12_resource_desc#alignment) does not mention that only Texture2D's can be used for small alignment. Upon passing Texture1D also to the API GetResourceAllocationInfo(), it does allow 4KB. So any reason this library has that turned off?

[thakral-shubham]

Reference line - https://github.com/GPUOpen-LibrariesAndSDKs/D3D12MemoryAllocator/blob/master/src/D3D12MemAlloc.cpp#L7796

[sawickiap]

You are right, the algorithm in function CanUseSmallAlignment is overly conservative. You can workaround this by predefining D3D12MA_USE_SMALL_RESOURCE_PLACEMENT_ALIGNMENT=2. I will change it to accept also 1D textures.

[thakral-shubham]

Thanks @sawickiap, I had already been using D3D12MA_USE_SMALL_RESOURCE_PLACEMENT_ALIGNMENT=2, but even in that, in HRESULT AllocatorPimpl::GetResourceAllocationInfo(D3D12_RESOURCE_DESC_T& inOutResourceDesc, UINT32 NumCastableFormats, const DXGI_FORMAT* pCastableFormats, D3D12_RESOURCE_ALLOCATION_INFO& outAllocInfo) const, there is a condition that inOutResourceDesc.Dimension == D3D12_RESOURCE_DIMENSION_TEXTURE2D, so this is what needs to be changed. In my local code, I have changed it to use both 1D/3D too.

[thakral-shubham]

Made the PR from my fork - #79