[quake3] Re: How does Quake 3 handle collisions when the actor collision area changes?

[Doug Winger]

>On 8/13/06, Tim Angus <tim at ngus.net> wrote:
>>On Sun, 13 Aug 2006 23:33:19 +0100 Asfand wrote:
>>  > How does Quake 3 handle collisions, when the model (and hence
>>  > collision area) changes frames, or directions?  E.g. a polygon is
>>  > right up against a wall, and it's not colliding with it.  The actor
>>  > changes direction, e.g. by turning away from the wall.  We assume this
>>  > is the player's character.
>>
>>Q3 uses AABB (Axially Aligned Bounding Box) collision detection,
>>which never changes state other than translation. As such the
>>problem you mention does not exist. In general, games engines use
>>simple collision for player physics and only use per poly collision
>>for hit detection, or rigid body dynamic simulations.
>>
>>
>
>So you're saying the AABB never changes size e.g. when the current
>frame of the animation changes?

Yes. In addition, the aas phase of map compilation sets up player
bounds by extending "structural" map faces, with the model's bounding
box centerpoint used for collision testing. Think of it as scaling
bounding areas of the map "inwards" and is why map files require
compiling.  This allows for quick determination  of bounds for
"floors and ceilings" as well. See the  bspc  section of code.

- Doug