The Star Citizen developer has confirmed that the game will be ditching support for DirectX entirely going forward in favour of the Vulkan graphics renderer API.
DirectX 12 and Vulkan are low-level graphics APIs that, if used correctly, can utilize the GPU much more effectively than previous iterations of DirectX and OpenGL. This leads to better frame rates and lower CPU usage in games.
"Years ago we stated our intention to support DX12, but since the introduction of Vulkan which has the same feature set and performance advantages this seemed a much more logical rendering API to use as it doesn't force our users to upgrade to Windows 10 and opens the door for a single graphics API that could be used on all Windows 7, 8, 10 & Linux. As a result our current intention is to only support Vulkan and eventually drop support for DX11 as this shouldn't effect any of our backers. DX12 would only be considered if we found it gave us a specific and substantial advantage over Vulkan. The API's really aren't that different though, 95% of the work for these APIs is to change the paradigm of the rendering pipeline, which is the same for both APIs."
Brown doesn't dismiss the possibility of DirectX 12 support for Star Citizen in the future. As he puts it, "DX12 would only be considered if we found it gave us a specific and substantial advantage over Vulkan". He also mentioned that the two APIs "really aren't that different".
The full Star Citizen will still be in alpha for quite a while, but the official website says Squadron 42, Star Citizen's single-player component, is due out later this year.