The Vulkan Portability Initiative is an effort inside the Khronos Group to develop resources to define and evolve the subset of Vulkan capabilities that can be made universally available at native performance levels across all major platforms, including those not currently served by Vulkan native drivers. In a nutshell, this initiative is about making Vulkan viable on platforms that do not natively support the API (e.g MacOS and iOS).
Press release for more information about macOS and iOS support
Mozilla is currently helping drive gfx-rs portability to use gfx-hal as a way to interface with various other APIs.
There are projects with the goal of taking another API and mapping it to Vulkan. The translation layer is in charge of taking in another API (for example OpenGL) and mapping it to equivalent Vulkan calls. It is important to realize that a translation layer is just translating and is not necessarily implementing Vulkan.
- The ANGLE project is an example of a translation layer for OpenGL to Vulkan. SIGGRAPH 2019 Presentation
- The DXVK project is an example of a translation layer for Direct3D 10/11 to Vulkan.
- There are many more layering projects as shown in chart below
