Invalid usage of VmaAllocation

[Eearslya]

Starting in chapter 3, Mesh Buffers, the guide introduces users to VMA. Buffers are created for vertices and indices, as well as host-visible staging buffers.

The guide instructs users to use staging.allocation->GetMappedData() to acquire a pointer to write to the staging buffer. However, this is not valid usage. VmaAllocation is an opaque type in VMA, and all of its members and functions are only visible to the single translation unit that defines VMA_IMPLEMENTATION. This works in vkguide's case because all of the code is within vk_engine.cpp, but it's probably not something we want to be teaching new users in a tutorial scenario.

All of the mentions of GetMappedData() should probably be replaced with the public API function vmaMapMemory().

[scgehin]

While we are at it, it would be best to access the mapped data from staging.info.pMappedData. Since the allocations are created with VMA_ALLOCATION_CREATE_MAPPED_BIT, calling the mapping/unmapping functions just adds extra work (though it's not an error).

[XavierCS-dev]

Thanks, switched to using allocation.pMappedData. This didn't fix my issues but at least it compiles now lol.