efficient mesh CSG library that runs on Android and has a permissive licence

https://forum.unity.com/threads/distributing-a-game-with-optional-vr-mode.898943/#post-7403534

https://github.com/amwatson/2DVrHybrid Objective: Launch a VR Activity from a 2D Activity (without changing applications) The new Steam Link app did something interesting: it started as a 2D app, but then launched into VR. Meta Quest always provided a way to run “flat” 2D Android phone/tablet applications inside the Quest Home environment – no VR-specific application code required. However, Quest doesn’t usually have hybrid apps: e.g. an app that starts as a 2D UI inside the Quest Home environment, and subsequently transitions into its own app-rendered environment at a later stage. It would almost certainly be useful: if applications could leverage the Quest 2D container for certain activities – i.e. showing interactive forms or deep-linking to web content – they could stand-up well-integrated, professional-looking 3D interfaces right away, and even re-use components across VR- and non-VR versions of their app. If you as an app developer tried to do what Steam Link did, you’d probably struggle. Some developers were asking how to make an app do this. As is sometimes the case, I don’t know if I know the right way, but I managed to figure out a way after a lot of experimentation.