DEVLOG 11 - BDA, Pipeline, Shaders

 
In the last devlog, I explained how I wanted to structure my bindless descriptor set. With that approach, I had a buffer for each data type. This approach works, but it’s a bit cumbersome, so I switched to using Buffer Device Addresses (BDAs). The idea behind it is: Create buffers, around VRAM, placing the buffers within VRAM memory pools. Instead of saving the physical data inside the descriptor buffer, we can only save pointers to the buffers, so I’ll have a buffer of pointers to the buffers scattered across VRAM. Since the pointers take up 8 bytes, managing the buffer is very simple, as it will be very light. So, essentially, I separate the physical data of the buffers from the shader binding logic.
 
Rather than using namespaces to hide the internal implementation, I chose to use Hadles, which are simply numbers that identify that resource. So I could have a BufferHandle, ImageHandle, SamplerHandle, PipelineHandle, and so on.
 
I chose not to call the structure that manages all this with names that might be reminiscent of the Vulkan API, but instead called this system Resource Mapper. At the moment, I think I’ve done something wrong with the code: Since the buffers are simply exposed via a 32-bit index, internally the buffer index corresponds to the index of the vector in which the Vulkan buffer handles and all the allocation information are allocated. I think I’ve erred in saving the buffers in vector indices that don’t match their exposed handle index outside of Eve. This causes access to incorrect buffers or buffers that don’t even exist, causing UBs or crashes. I still need to verify this issue and, if it occurs, I’ll have to fix it.
 
Furthermore, yesterday I added all the code responsible for creating the graphics pipeline and compiling the shaders. This code is still a bit rough and needs improvement.
 
Furthermore, since I don’t want the user to have to manage synchronization outside of the engine, I’ve been thinking about how to structure a Render Graph. I saw Frostbite’s presentation at GDC 2017 where they explained how their Render Graph works and that gave me some insights.