I kind-of assumed that if you said USE_GEOMETRY that the collision engine would
do an initial sweep using a realy stupid spherical bounds model, discard every
pair that are clearly not colliding, and then perform the clever, accurate
geometry collision test. Am I wrong?
"Leung, Sunny" wrote:
> Hi Justin,
>
> Thanks for your response to my question in J3D interest group.
>
> I have tried the USE_BOUNDS method in the collision constructor instead of
> the USE_GEOMETRY parameter. Although the speed has increase significantly
> from the 8mins to 14sec., the accuracy of such method is unacceptable. Is it
> possible to setup a CollisionBounds around an object using its shape3d
> information (vertices information).
>
> Instead of separating collidable and non-collidable objects in the
> scenegraph. Is it possible to instruct the collision detection node to only
> perform collision detection within a certain radius (volume) around an
> object. For example, if there is no objects within a 2 meters radius of a
> particular object (Object A), the collision detection will not be activated.
> If another object (Object B) is within the 2m radius of Object A, the
> collision detection node will activate and detect any possible collision
> between Object A and parts of Object B which are within the 2m radius of
> Object A.
>
> If the above approach is possible, it will greatly reduce CPU time (even in
> USE_GEOMETRY mode) and at the same time maintain high level of accuracy.
>
> Please comments.
>
> cheers,
> Sunny Leung
>
> -----Original Message-----
> From: Justin Couch [mailto:[EMAIL PROTECTED]]
> Sent: Monday, July 26, 1999 1:14 PM
> To: [EMAIL PROTECTED]
> Subject: Re: [JAVA3D] Optimising collision detection in J3D
>
> Leung, Sunny wrote:
>
> > 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?
>
> There are two things that you need to do. Firstly, for any objects that
> you _don't_ want to collide with, you turn collision detection off using
> setCollidable(false) defined in Node. The easiest way to do this is
> partition the scene graph into two groups - collidable and not
> collidable areas. Then, the parent group of all the not collidable stuff
> you setCollidable(false). This then works for all children of the group
> so that you don't need to explicitly set it.
>
> Next, you set the bounds for the objects you do want to collide with
> using the setCollisionBounds method of the parent group of the
> collidable object (defined in the Group class). If you want a spherical
> bounds for your object use BoundingSphere as the object that you set.
>
> Finally, when constructing your behaviour criterion, make sure you set
> it with the Node and the speed hint of USE_BOUNDS. I think you can also
> use the constructor that takes the Bounds reference and it automatically
> uses the USE_BOUNDS speed hint, but the docs aren't particularly clear
> on this.
>
> --
> Justin Couch Author, Java Hacker
> Snr Software Engineer [EMAIL PROTECTED]
> ADI Ltd, Systems Group http://www.vlc.com.au/~justin/
> Java3D FAQ: http://tintoy.ncsa.uiuc.edu/~srp/java3d/faq.html
> -------------------------------------------------------------------
> "Look through the lens, and the light breaks down into many lights.
> Turn it or move it, and a new set of arrangements appears... is it
> a single light or many lights, lights that one must know how to
> distinguish, recognise and appreciate? Is it one light with many
> frames or one frame for many lights?" -Subcomandante Marcos
> -------------------------------------------------------------------
>
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