Re: Anyone working on Collision Detection yet?

Art Yerkes ([email protected])
Fri, 20 Oct 1995 19:08:25 -0500


> From [email protected] Fri Oct 20 18:31 CDT 1995
> Date: Fri, 20 Oct 1995 12:31:16 -0400 (EDT)
> From: Braddock <[email protected]>
> X-Sender: [email protected]
> To: Vassilis Bourdakis <[email protected]>
> Cc: VRML-Mailing List <[email protected]>
> Subject: Re: Anyone working on Collision Detection yet?
> Mime-Version: 1.0
>
> On Thu, 19 Oct 1995, Vassilis Bourdakis wrote:
> > Hello all,
> > as tme subject says, I'd just like to know what is tme status
> > of work done on collision detection.
>
> > It seems that there are many proposals on various behaviour
> > aspects, but not a lot of discussion on collision detection.
> > I don't know if some of you consider it a bahaviour as well
> > (not me though) but I think it is something that could be
> > achieved easier (in terms of specification that is) than
> > behaviours and I feel that it is equally important!
>
> CONCEPTUALLY it really is the same as behaviors. The only
> difference is that it really needs to be fast (not scripted, well
> integrated).

This is probably the best deffinition of collision. Which brings up another
point, some are talking about collision as a behavior of objects. How do the
objects communicate their position to each other?

Possible models:

1 Object "a" polls moving objects to see if they collided with it.
2 Object "a" makes a bounding box check of each object, followed by (1)
if a collision occurred.
3 Object "a" knows where other objects are going to move, and plans
a collision with another object.

Another issue I might raise is about collision in hirearchial models, which
may make for some messy mathematics, and long computations.

Consider:

Two knights fighting in an interactive game.

(Knight in armor) owns (knight arm) owns (knight hand) owns (sword)
colliding with:
(Knight in armor) owns (knight hsad).

(A typical occurrence in such a game)

The natural question to answer first (in my opinion), is should
collision detection be a behavior of the two nights, using their
own specialized algorithm, or should a general algorithm be
evaluated for the nights, or for their parts.

>
> My suggestion for an approach to behaviors which are common and must be
> FAST: Get the behavior very standardized and implimentable as scripts.
> At this point browser writers, to improve their browser performace,
> should internalize the behavior code, allowing it to bypass the API when
> accessing the accessable scene-graph and run as fast compiled code.
>

Collision detection should not be scripted (IMHO).

> HOWEVER, I think the general framework for VRML should not limit it to
> mearly sharing data representing 3D physical spaces. No reason why the
> same standard suite can't be used for whiteboarding and conferencing, etc.
>


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