Most popular open-source, free, well-documented game engine for research application [closed]

Question

My company is getting ready to propose a stroke and brain-injury rehabilitation tool and we need to know what free, open-source, and well-documented game engine are out there.

• We will be constructing a 3D environment.
• We will need to have good control over characters fine motions (for instance even finger motions).
• We need a good physics engine including collision detection and inverse kinematics if possible.
• It would be very useful if there are already some hooks in the code for providing haptic feedback, but that's not necessary.
• Graphics do not need to be phenomenal.
• It must be relatively easy to throw together a proof of concept.

I'm predisposed toward Jake2 because Java's dead easy to program in, but I need more options to consider from you folks who have experience.

Answer 1

I would consider looking at ioquake3 which is an opensource port of Quake 3. Also, I would like to point out the excellent Delta3d which is a DoD funded and developed opensource simulation engine.

Notre Dame evaluates several engines in the paper A Survey of Collaborative Virtual Environment Technologies. I would think that this would be best starting point as you will be able to access alot of existing knowledge on engines when applied to virtual environments.