Open Source FPS engine

I am looking to port ioquake3 engine to Java. And use the resources from OpenArena for content.

Not sure how far I gonna get though, the codebase is extremely hard to follow. I have found a port of Quake 2 codebase to Java (Jake 2) but its not very Java like. I still can’t figure out how Potentially Visible Sets (PVS) are used to render the scene.

So does anyone have Java code (or even OO code in C++) for working with BSP maps? I already found some GPL code for viewing MD3 models.

I also considering using jME. At this stage though I got no idea on how I can leverage the OpenArena content with jME. Models are in Blender and Maps are in MAP format.