Spec clarification regarding VkAccelerationStructureBuildRangeInfoKHR::primitiveOffset

[cmannett85-arm]

In the spec it states:

VUID-VkAccelerationStructureBuildRangeInfoKHR-primitiveOffset-03657
For geometries of type VK_GEOMETRY_TYPE_TRIANGLES_KHR, if the geometry does not use indices, the offset primitiveOffset from VkAccelerationStructureGeometryTrianglesDataKHR::vertexData must be a multiple of the component size of VkAccelerationStructureGeometryTrianglesDataKHR::vertexFormat

The 'component size' seems like an odd choice since there are formats with different sizes of components, but it seems wrong when you consider that VkAccelerationStructureGeometryTrianglesDataKHR::vertexData uses a stride when being read from. So shouldn't constraint VUID-VkAccelerationStructureBuildRangeInfoKHR-primitiveOffset-03657 specify that the primitiveOffset be in multiples of VkAccelerationStructureGeometryTrianglesDataKHR::vertexStride?

[dgkoch]

Hi @cmannett85-arm,

We discussed on the Ray Tracing TSG on 10/17.

We agree the component size alignment requirement is a bit odd, at least for packed- or sub-32-bit components, however it does largely make sense for 32-bit or larger components.
However we also don't think that multiple of vertexStride is the correct thing either.
We've created an internal issue to further discuss and attempt to clarify: https://gitlab.khronos.org/vulkan/vulkan/-/issues/4058