Hey, another view. Blender teamed up with Unity is the best VR/AR solution at the moment. Bake your scences down with cycles in batch bake non view dependent and then go to Unity and lit it with and spherical HDR rendered in Blender for the view dependent stuff. You will get some fotoreal results in VR/AR with 90fps then.
Would like some more Light Field Rendering would be possible with cycles. But it will come soon. ) Has anyone tried Octane with Blender in direction LightField Rendering.
Yo, 'sup. Focusing on just small portions of your initial post:
Yeah, I’d say Godot is the open-source variant of Unity, and it’s been getting work pretty regularly - that might be the way forward for you, if you’re interested in something like Unity, but more open.
UPBGE, I don’t know about - I don’t stay very much up-to-date with the state of the BGE at the moment, but it’s something to consider too.
BDX is the engine I use, and while it is NOT nearly as advanced as Unity or even the BGE, it’s got a small code-base, it’s open-source, it integrates with Blender directly, and it is actually running on LibGDX, so you do have all of that cross-platform integration. Armature animation is something that was missing from BDX that I just about got working, as well, which I know VR usually uses heavily. The thing I like the most about BDX might be that light, simple code-base, actually, since it’s pretty easy to add features to and understand when bugs arise.