Perhaps the J3D people can talk more about exactly what collision is being used and
what their long term plans are?
It may be worthwhile to appeal to the J3D gods to write support for highly accurate
collision detection directly into J3D.
Something accurate ( if not extremely fast ) could be done in fairly short order by
leveraging off of the freely available sources.
I'm using a variation of one of the below cited packages with J3D myself.... mine is
not public however. Accurate collision
detection is critical for simulations so probably everybody is going to port one of
these unless J3D beefs it out themselves. And
it seems to fall in their domain because J3D is more than just a scenegraph - it has
behaviors and events which do relate to
collision.
- Andy
-----Original Message-----
From: Tony Burrows <[EMAIL PROTECTED]>
To: java3d-interest <[EMAIL PROTECTED]>
Cc: Edward K. O'Neil <[EMAIL PROTECTED]>
Date: Monday, June 07, 1999 5:03 PM
Subject: Re: [java3d] multiple Shape3Ds and collision detection
>At 15:03 07/06/99 -0400, you wrote:
>>
>>All--
>>
>> I've noticed that there's a lot of trouble out there with collision
>>detection and the 3D API and have gone through several different
>>possibilities trying to figure this out. I've had significant trouble
>>with this myself for anything but the simplest 3D shapes. Initially, I
>>had a 3D object composed of Primitive subclasses (Cylinder, Cone, etc...)
>>and couldn't ever get collision detection working on those shapes (whether
>>as standalone shapes or composed together in some more complex object).
>>
>
>I've had similar problems Edward - though I haven't tried complex shapes
>yet. The trouble with collision detection is it is ****ed hard to do.
>Just llok at some of the algorithms out there for it. I suspect that if we
>want decent CD then we'll need to look at V-Clip, I-Collide, RAPID etc and
>none of those have been ported to Java yet (though I just might do it for
>V-Clip). The J3D collision detection just doesn't provide enough info to
>be really useful except in the VRML collision detection sense (which is
>probably where it came from).
>
>As far as collision detection with primitives goes, it is do-able, 'cos
>I've done it although only between a sphere as a Primitive and a Box cast
>into Shape3D (the sphere wasn't). It did need a couple of changes from the
>example collider:
>
>The ball was a snookerBall class, extending TransformGroup:
>
>public snookerBall(double xpos, double ypos, double zpos, double rad){
> t.set(1, new Vector3d(xpos, ypos, zpos));
> setTransform(t);
> setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
> setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
> M.setCapability(Material.ALLOW_COMPONENT_WRITE);
> app.setMaterial(M);
> // alt to shape3D for ch1 - 1 line but needs collider changed too & setCap
>type change
> Primitive ch1 = new Sphere((float)rad, Sphere.GENERATE_NORMALS |
>Sphere.GENERATE_TEXTURE_COORDS, 20, app);
> ch1.setCapability(Primitive.ALLOW_COLLISION_BOUNDS_READ);
> ch1.setCapability(Primitive.ALLOW_COLLISION_BOUNDS_WRITE);
> BoundingSphere bs = new BoundingSphere(new Point3d(0.0, 0.0, 0.0), rad*2);
> ch1.setCollisionBounds(bs);
> addChild(ch1);
>
> file://collision detection
> collider cd = new collider(ch1, this);
> BoundingSphere bounds = new BoundingSphere(new Point3d(0.0, 0.0, 0.0),
>100.0);
> cd.setSchedulingBounds(bounds);
> addChild(cd);
>
> // now for the physics values; velocity already set to zero;
> radius = rad;
> height = ypos;
> }
>
>and the collider behaviour:
>
>public class collider extends Behavior {
> private boolean inCollision = false;
> private WakeupOnCollisionEntry wEnter;
> private WakeupOnCollisionExit wExit;
> private WakeupOnElapsedTime wElapsed;
> private WakeupCriterion[] wInTime;
> private WakeupCriterion[] wOutTime;
> private snookerBall p;
> private Node shape;
>
> public collider (Node s, snookerBall daddy) {
> p = daddy;
> shape = s;
> inCollision = false;
> System.out.print("Collider Created ... ");
> }
>
> public void initialize() {
> wEnter = new WakeupOnCollisionEntry(shape);
> wExit = new WakeupOnCollisionExit(shape);
> wElapsed = new WakeupOnElapsedTime(5);
> wInTime = new WakeupCriterion[2];
> wInTime[0] = wEnter;
> wInTime[1] = wElapsed;
> wOutTime = new WakeupCriterion[2];
> wOutTime[0] = wExit;
> wOutTime[1] = wElapsed;
> wakeupOn(new WakeupOr(wInTime));
> System.out.println("Initialized");
> }
>
> etc...
>
>Hope this is of some use. I've got the complete files if you want them,
>and refs to some collision detection systems.
>
>Tony
>
>
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