Validation error when creating (some) images with an allocator with tight alignment enabled (fix proposal)

[rtryan98]

When creating resources, the allocator will add the D3D12_RESOURCE_FLAG_USE_TIGHT_ALIGNMENT flag, independently of the resource dimension.

Because images aren't supported with tight alignment, and the allocator properly changes the provided alignment of 0 to the correct value, the following validation error appears:

ID3D12Device::GetResourceAllocationInfo2: D3D12_RESOURCE_DESC::Alignment is invalid. The value is 4096. When D3D12_RESOURCE_DESC::Flag bit for D3D12_RESOURCE_FLAG_USE_TIGHT_ALIGNMENT is set, Alignment must be 0. [ STATE_CREATION ERROR #721: CREATERESOURCE_INVALIDALIGNMENT]

Adding a check for inOutResourceDesc.Dimension == D3D12_RESOURCE_DIMENSION_BUFFER here fixes the issue.

D3D12MemoryAllocator/src/D3D12MemAlloc.cpp

Lines 7819 to 7825 in 2ac8a9b

	if (IsTightAlignmentEnabled() &&
	// Don't allow USE_TIGHT_ALIGNMENT together with ALLOW_CROSS_ADAPTER as there is a D3D Debug Layer error:
	// D3D12 ERROR: ID3D12Device::GetResourceAllocationInfo: D3D12_RESOURCE_DESC::Flag D3D12_RESOURCE_FLAG_USE_TIGHT_ALIGNMENT will be ignored since D3D12_RESOURCE_FLAG_ALLOW_CROSS_ADAPTER is set. [ STATE_CREATION ERROR #599: CREATERESOURCE_INVALIDMISCFLAGS]
	(inOutResourceDesc.Flags & D3D12_RESOURCE_FLAG_ALLOW_CROSS_ADAPTER) == 0)
	{
	inOutResourceDesc.Flags |= D3D12_RESOURCE_FLAG_USE_TIGHT_ALIGNMENT;
	}

[vdwtanner]

D3D12_RESOURCE_FLAG_USE_TIGHT_ALIGNMENT is not constrained to only buffers. Drivers are allowed to align textures more tightly when the flag is present, but there are no explicit requirements specified for tier 1. See the final statement in the placed resources section: https://microsoft.github.io/DirectX-Specs/d3d/D3D12TightPlacedResourceAlignment.html#placed-resources.

Regarding the strict requirement on D3D12_RESOURCE_DESC::Alignment being 0 when D3D12_RESOURCE_FLAG_USE_TIGHT_ALIGNMENT is set, I've heard feedback from a few sources now about this and I'm considering relaxing that in a future AgilitySDK.

[sawickiap]

Thank you for reporting this issue. I propose disabling automatic usage of "small alignment" when "tight alignment" is enabled in function AllocatorPimpl::GetResourceAllocationInfo. which hopefully solves the problem. I've changed it on my fork for now. Please let me know whether it works for you.

https://github.com/sawickiap/D3D12MemoryAllocator