Bounding boxs why?

#1 All games use bounding boxes, for a very good reason.
I can't explain everything, but one thing is, that if you have no bounding box, models can get stuck into other models VERY easily...

#2 Oh wow didn't know that... where is it in quake 3? because I never remember having to to put them in...is it just in the code?

...anyway then how can I do different things like prone? how do I change it on the fly?

#3 bounding boxes are used to get a general idea if the model has collided with something or not. What some developers then do is have a bounding box aroudn the character, then hit boxes, then maybe smaller boxes for precise damage, but this way it won't have to check the hitboxes every turn (thus wasting processing power). So if you use bounding boxes with hit boxes, you only check to see if the hitboxes are being hit if the bounding box has a collision. Although some engines (like torque wihtout modification) only uses a bounding box.

the bounding box would be in the code, as it just takes the farthest points and makes a box around those points.

Other than that bounding box's are used to make very general collision detection so that you don't take too much processing power, but still keep people from running through walls, terrain, etc..

--KallDrexx

#4 some games have implied bounding boxes, but still do hit detection against the model.

#5 Basically a bounding box, which is represented by very simple geometry(a cube like shape) is much faster to do hit detection and collision against. As compared to the complex geometry of say the player model.

So as a quick first test, you just check the simple bounding box representation of the object, if the test passes(you hit the box) then you move on to do the more expensive model geometry testing(we hit the arm?/head?/whatever). If it fails you move on to the next bounding box test for the next object.