Guild of Writers

Would it be possible to add physical bounds to a gear? I've tried it in the past without success. It's like the bounds aren't precise enough.

It might be a problem with your bounds type. For complex meshes like gears you must use Triangle Mesh (but it increases a bit the Age loading time).
Maybe you used Convex Hull, and this one isn't really precise (IIRC the games itself creates the faces and tries to make the biggest mesh with your vertices coordinates but it doesn't care to match the visible part, or something like this. It is more complex than Box or Sphere but not as precise as Triangle Mesh. It is loaded more quickly).
Box (and Sphere) is the smaller mesh that encompasses your object. They are quick to load but remains very simple.

Is it the problem ?

if you're trying to animate a mechanism it would be much simpler to make an animation during modelisation and then play it in the engine. Game engines are not really designed to do complex physics interactions (at least not Plasma).

If the physics involved are to complex to animate by hand you can always try a physics simulation in your modeler and then bake it as an animation. (if you're using 3ds that would be done by using Havok's reactor tools).

One of my partners, Jason Lindon, tried to make a simple cart with wheels - to see if it could be pushed. Not surprisingly, it didn't quite work as planned. Occassionally, the cart would move a short ways before literally exploding. Sometimes the cart could be pushed back and forth, and the wheels would turn. However, inevitably, each part (wheels and body) would go on separate (and violent) vacations.

After the explosion (sorry, not sure how else to explain it), sometimes the wheels or cart body would become lodged in the floor or inside/intersected with another object.

The blend is his experiment, but if he gives me permission, I'll post a link.

As far as "why" the cart doesn't happily roll to and fro is still an object of investigation. It could be the PhysX engine, or could even be due to the poly count (detail) of the intersection areas of the objects (e.g. the inside of the wheels where the axles go, or the axles themselves.). It could even be due the shape of the outer circumference of the wheels.

Regardless, I'll ask if he minds having his blend publicly downloadable. If so, I'll add a link to this post so you-all can play around with it. Lol, if nothing else it is cool to see what happens.

What I pretty much thought. Thanks guys for a surprising amount of info on the subject. Very interesting problem. If i come across any further explanations, I'll post links to them.

For the cart, it isn't a really good idea to have many kickables inside each other as you would usually do for wheels in real life (it also increases lags). I think making the wheels part of the main mesh would be better (but it won't rotate).

Something a LOT better: use the driving brain (as the Zandoni in the Cleft). The games rotates the wheel meshes automatically, the physics should be better than with kickable, and of course you could even drive it. Another positive thing: you could use Box bounds instead of Triangle mesh.

@Sirius. That's a great idea. Thanks for the tip.