You're definitely on the right track. High performance collision schemes
often use a multi-leveled approach with lots of cheap tests to weed out
obvious misses and saving the expensive tests for last. The particular
kinds of tests and number of levels is application dependant. It depends on
whether you are dealing with a static world and a single dynamic player (the
user avatar) or whether you have lots of "players" moving about. This is
true in general, not just Java 3D.
The cheapest test is to perform amongst multiple dynamic players is time to
collision estimates on all objects based on their current speed (not
velocity): If there is no way an object can hit another object given its
present speed no matter which direction it is going then eliminate it as a
collision candidate. Unless all players are in the same general area this
will significantly cull the collision list. Intersecting radii between
pairs of dynamic players and large simple bounding shapes and planes for
static world objects (e.g. the ground plane) is a good next test. The next
level of collision test might be axis aligned bounding boxes or non-axis
aligned bounding planes, which are easy to intersect. The final test is
against the actual geometry of the two colliding objects, which can be
pretty expensive. You can also consider doing a partial collision test
between porcupine-like "quills" on one player and the polygons on each of
its candidate collision target. You also have to start worrying about the
possibility that objects may have passed through one another between frame
times.
Hope this helps.
--jon
____________________ Peculiar Technologies ____________________
Jon Barrilleaux 3800 Lake Shore Ave. Purveyors of
[EMAIL PROTECTED] Oakland, CA 94610 Alternate Reality
510.444.4370 voc Augmented Simulation
510.444.0231 fax www.augsim.com and 3D Solutions
> Date: Mon, 26 Jul 1999 13:35:13 +1000
> From: "Leung, Sunny" <[EMAIL PROTECTED]>
> Subject: Optimising collision detection in J3D
>
> Hi all,
>
> Is it possible to perform collision detection only on a certain volume
> around an object. For example, I have a large virtual universe with many
> objects (two of them are fairly complicated with around 3000 faces each).
> I
> have attached a collision detection behavior nodes on one of the object
> and
> report collision if it collide with any other objects in the scenegraph.
> At
> the moment, this collision behavior nodes is detecting collision with all
> objects in the scenegraph and this really slow down my program. (actually,
> it's taking 8 min per point its travel).
>
> So is it possible to tell the collision detection node to detect collision
> only within a certain radius (volume) around the object which the node is
> attached onto?
>
> Please comments.
>
> Sunny Leung
>
>
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