Depends upon the gravity you're talking about. If you're talking about true gravity, objects being attracted to each other, I haven't seen any of it.
If you're talking about just getting the guy to go down if he steps off a cliff you just need collision with the world and a force always pushing the object downward. Please post your code though, there's always a new wrinkle to everything, and we're interested to see what you've done.
Crazy Donut Productions, Current Project: KillZone
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