From https://crbug.com/dawn/1216#c9:

@RafaelCintron:

Though the D3D12 API does not forbid copying between resources whose dimensionality does not match (1D rows <-> 2D rows, 1D rows <-> 3D rows, and 2D slices <-> 3D slices) the behavior is undefined unless you check the TextureCopyBetweenDimensionsSupported field of the D3D12_FEATURE_DATA_OPTIONS13 struct and find that it is true. The flaky behavior we're seeing is up to the whims of the driver.

To get portable behavior, we'll need to either forbid these operations for WebGPU v1.0 or workaround the limitations by copying the data first to a buffer and from the buffer to the final destination.

@austinEng:

Wow - the fact that this is in D3D12_FEATURE_DATA_OPTIONS13 is a little discouraging.
"Minimum supported client Windows 11, version 22H2; or DirectX 12 Agility SDK 1.6 or later"

perhaps we need to forbid this in the spec after all.