How to write to the image directly by CPU when load it in Vulkan?

Question

In Direct3D12, you can use "ID3D12Resource::WriteToSubresource" to enable zero-copy optimizations for UMA adapters.

What is the equivalent of "ID3D12Resource::WriteToSubresource" in Vulkan?

Answer 1

What WriteToSubresource seems to do (in Vulkan-equivalent terms) is write pixel data from CPU memory to an image whose storage is in CPU-writable memory (hence the requirement that it first be mapped), to do so immediately without the need for a command buffer, and to be able to do so regardless of linear/tiling.

Vulkan doesn't have a way to do that. You can write directly to the backing storage for linear images (in the generic layout), but not for tiled ones. You have to use a proper transfer command for that, even on UMA architectures. Which means building a command buffer and submitting to a transfer-capable queue, since Vulkan doesn't have any immediate copy commands like that.

A Vulkan way to do this would essentially be a function that writes data to a mapped pointer to device memory storage as appropriate for a tiled VkImage in the pre-initialized layout that you intend to store in a particular region of memory. That way, you could then bind the image to that location of memory, and you'd be able to transition the layout to whatever you want.

But that would require adding such a function and allowing the pre-initialized layout to be used for tiled images (so long as the data is written by this function).