Here's one I wasn't aware of, developer Erik “kusma” Faye-Lund from Collabora has been working on Zink. It's a new OpenGL implementation that works on top of Vulkan. It's a "Mesa Gallium driver", which aims to provide "hardware accelerated OpenGL when only a Vulkan driver is available".
Writing about the work in a blog post, the developer talked a little about why they're doing it. Their aims include: simplifying the graphics stack, lessening the work-load for future GPU drivers, enabling more integration and supporting application porting to Vulkan. Sounds like some pretty useful goals to me. They do go into more detail on each point, which is worth reading. The idea of everyone targeting Vulkan in future, with something like this being used for OpenGL is quite interesting if it could ever happen.
While it's still early days for the project, it's currently only supporting OpenGL 2.1, and OpenGL ES 1.1 and 2.0 plus some extensions and so it has some ways to go before it's truly useful. Even so, it sounds exciting and they show off some simple games working with it already. Dave Airlie from Red Hat has also been jumping in, with work on OpenGL 3.3 progressing so it looks like it might move forwards quite quickly.
See more about it here.
Hat tip to Joe from our Telegram Group.