It's not exactly hard to guess, given there are only a limited number of "proper commercial physics engine..".
I mean your choices effectively boil down to either:
Renderware: Physics (aka Karma) or Havok.. and yup that's pretty much it.
ODE (Open Dynamics Engine) is free, open-source, and is actually the younger-brother of Karma (what is know called Renderware: Physics). The guy who wrote ODE was the same guy who wrote the original Kea Dynamics for Karma.. ODE has quite a bit of Kea in it too. It's also professionally used by a number of companies; Most recent I can remember is Blood Rayne 2.
So it's not like ODE is some wannabe Physics Engine. It's quite a damn sight easier on the Processor actually than Havok which is just horrible. Newton is extremely awesome in this respect, as it is very cheap on the processor; however a huge problem I have with the engine is it's realistic. While most people would say something along the lines of "but aren't games companies striving for realism?", this is really only true to an extent. Gameplay MUST be fun, if the player isn't going to enjoy what they're doing then it kills the game's feel. Driving games for example require A LOT of leaway from realism in order to make them enjoyable.. too much realism and people get frustrated becuase you peel off from the starting line in WRC 2005 and end up doing a wheel spin; or smash into a post at 110MPH and the car gets wasted.
No one wants that sort of realism, but at the same time if you don't add the car damage and a fairly accurate in the eyes of the end-user who's only rally experience is WRC on Eurosports, then you know they don't realise it takes years and years of training to get THAT good with a car. They want to be able to do that stuff without needing years of skill. ^_^
What gets me is I thought the original one was based on something being done by an Ex-Codemasters guy called Philip. Might be getting mixed up with another project though.
Anyways.. should be interesting to finally see the results of this secret physics experiment that's been going since like forever.
