There was once a version of Linux with a 3D desktop - called project looking glass. It was essentially a java app (employing scene graph technology from java 3d) used to interoperate with X-Org desktop environment. It turned X-Org into a cross between a 3D gaming environment and a desktop - much more impressive than 3D desktop effects that you get with compiz, etc. The project was going to be ported to Windows and MAC, but Sun pulled the plug due to other priorities.
Nowadays, there are more java 3D tools, as well as the more concise programming language of Kotlin. So. hypothetically speaking, if Haiku had 3D acceleration, some java 3D tools, and Kotlin - how difficult would it be to create a 3D desktop environment in Haiku compared to Linux - i.e., how hard would it be to interoperate a java 3D app with the Haiku desktop/window manager code?