This document describes the principal alternatives users can pick from.
If you have a computer with Windows installed, you can and should use the official driver which came with your GPU. While D3D9 is considered a legacy technology, it will be supported for a long time to come.
This is Wine’s D3D9 implementation which converts the API calls to OpenGL.
However, historically OpenGL had issues with CPU / driver overhead, perhaps even more so than D3D9, and while the GPU performance is good, in most benchmarks this implementation is CPU limited.
There are a few tehniques for reducing the CPU overhead. For example, Wine implements Command Stream Multithreading, which allows WineD3D to take better advantage of the multiple cores found in modern PCs. Unfortunately, performance is still somewhat lacking.
VK9 is an alternative to this project, which aims to convert D3D9 to Vulkan directly.
With all due respect for Mr. Schaefer’s work on VK9, I believe it’s a very hard task to convert a legacy API like D3D9 directly to Vulkan.
Even DXVK, which converts D3D11 calls to Vulkan, is a very complex library.
I believe a more layered approach, i.e. converting D3D9 to D3D11, is better, since there is already a lot of work done for us by DXVK, the layer on which we build, which performs the D3D11-to-Vulkan conversion.