Bounding Volume

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aleradish
Posts: 22
Joined: Thu Mar 05, 2009 9:41 pm

Bounding Volume

Post by aleradish »

Hi,

I make my compliments first of all, to Erwin Coumans and all developers for his works that I appreciate so much. I've used for university project bullet and in some blender animations and I had some fun with that:).
Now I would like to make a thesis with the bullet structures. I need to use Raycast, and bounding volumes for controlling the elements of the scene to find the best camera. I need to use bullet optimized structures for that.
Is there a possible to use oriented bounding volume, spheres volumes or discrete object politope? I need to use these other kind of bounding volume if it is possible...but I've seen that all examples I've seen are using btAxisSweep thit AABB..

Is there a possibility. Compliments to all and I wait with impatience to use SPH fluid when it will be possibile :shock: ...I will have a lot of fun! :D

Thanks to All.
aleradish
Posts: 22
Joined: Thu Mar 05, 2009 9:41 pm

Re: Bounding Volume

Post by aleradish »

AnyOne can tell me... only if a different kind of bounding volume is possible in Bullet?
Only that:)
rrck
Posts: 26
Joined: Mon Sep 21, 2009 7:30 am

Re: Bounding Volume

Post by rrck »

Hello,
I'am only Bullet user, so I may be not fully correct. :)

As I know AABB are used mostly for broadphase part of collision detection, and I have not noticed in documentation any mentions about possibility to use other bounding volumes (as I know AABB is most optimal for broadphase).

May be you can use collision object with different collision shapes for your task?
aleradish
Posts: 22
Joined: Thu Mar 05, 2009 9:41 pm

Re: Bounding Volume

Post by aleradish »

But I didn't understood... The bounding Volumes are the collisionShapes in Bullet Engine? In the Broadphase algorithm the AABBs are used for locating the probably collisions.. between the collisionShape? That's right?

Thank you so much....
ola
Posts: 169
Joined: Sun Jan 14, 2007 7:56 pm
Location: Norway
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Re: Bounding Volume

Post by ola »

I'm not sure if I understand your original question correctly. If you want to do a raycast against some bounding volumes defined by you, then you can just create a rigid body with a collision shape of your choice to represent that volume.

I think what you call bounding volume is in fact a collision shape in Bullet. Bullet's bounding volume is an AABB that encloses this collision shape. Normally you won't have to deal much with that AABB directly.

The collision shape is often a simple convex shape like a sphere, box or convex hull shape (your polytrope?) that approximates the real shape of the object (the rigid body) you are simulating. It's up to you to choose this collision shape. The collision shape's orientation follows the orientation of the rigid body.
aleradish
Posts: 22
Joined: Thu Mar 05, 2009 9:41 pm

Re: Bounding Volume

Post by aleradish »

Ok:) I understood the question I think... the AABBs are used only to make the broadphase algorithm but the real Bounding volumes are the collisionShapes.. Like that I don't have to worry about shape approximation.

Thank you so much!!! :)
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