Hi all,
I’m new to the forum. I have read it in the past and it was full of useful info. 
Anyway I’m working on a Java game called http://roboforge.com/ it uses Java3D, Swing, and it’s own physic engine. It was released in 2000. The games when under and eventually went Quasi-Open Source. At which point I started working on it.
The premise of the game is you build robots with Lego like parts, and then program them to fight in on-line tournaments.
I have been fixing many of the problem with the game, that cause it to die to begin with. Now I’m at a point where major decisions need ot be made about what engines the game need to be using. Hopefully the member of this board can help me out. 
The physic engine is the biggest question for me. The one the game uses has many many flaws. 
I have a rudimentary knowledge of physic engines, and I worked with ODE for a bit. What would be a good physic engines to use for my game?
I have fixed most of the Swing/Java3D multi threading problems, but I think removing Swing all together would make the code easier to work on in general, but doing that it a lot of work. So what would be a good replacement for it? I don’t know if it possible, but I would like to put the UI onto a Canvas3D; but that is not a requirement.