The version of DirectX introduced in Windows 10 in 2015. A major change was adding very low-level programming interfaces (APIs) so that developers can obtain more parallel operations. Support for multiple GPUs was added, which previously was handled by the GPU vendor. In 2018, real-time ray tracing was added to DirectX 12 and Windows 10.
DirectX 12 Ultimate
In 2020, DX 12 Ultimate updated its ray tracing to Version 1.1, which added three features. GPU shaders can invoke ray tracing without a round trip to the CPU. Streaming engines can load shaders more efficiently, and inline ray tracing lets developers handle more of the processing. See DirectX
and ray tracing