3D Window Managers/Desktop Environments for Linux?

I'm compiling a list of known 3D window managers for Linux. Does anyone know of any others besides the following? 1. [Ibex](http://hwahba.com/ibex/) 2. [Maze Compositor](https://github.com/capisce/mazecompositor) 3. [Januz VR](https://hackaday.io/project/5077-metaverse-lab/log/19096-x11-application-migration-pt-1#discussion-list) 4. [Motorcar](https://github.com/evil0sheep/motorcar) Ideally they would be demoable/usable in VR, but not necessarily :)