Search found 849 matches

by drleviathan
Wed May 20, 2015 4:03 pm
Forum: General Bullet Physics Support and Feedback
Topic: Disappointed with Bullet physics simulation speed...
Replies: 9
Views: 7958

Re: Disappointed with Bullet physics simulation speed...

I'm wondering: are you sharing the box shape? When multiple boxes have the same dimensions you can make one btBoxShape instance and give that to each RigidBody that needs it -- this should help things run a little faster (less cache misses), but I don't know by how much since I haven't experimented.
by drleviathan
Mon May 18, 2015 5:03 pm
Forum: General Bullet Physics Support and Feedback
Topic: Spheres show strange behaviour.
Replies: 6
Views: 4514

Re: Spheres show strange behaviour.

If you set the sleeping velocity thresholds too low then your objects will never settle! If you want that behavior just for those objects (and not the rest of the world) you can call btRigidBody::setActivationState(DISABLE_DEACTIVATION) instead.
by drleviathan
Mon May 18, 2015 4:00 pm
Forum: General Bullet Physics Support and Feedback
Topic: Spheres show strange behaviour.
Replies: 6
Views: 4514

Re: Spheres show strange behaviour.

In Bullet 2.8.2 the default values for linear and angular sleeping velocities are: 0.8 m/sec and 1.0 radians/sec respectively. These are hard-coded magic numbers in the btRigidBody constructor implementation. You'll have to experiment with different values to find something that works for you, altho...
by drleviathan
Mon May 18, 2015 12:59 pm
Forum: General Bullet Physics Support and Feedback
Topic: Spheres show strange behaviour.
Replies: 6
Views: 4514

Re: Spheres show strange behaviour.

Bullet will deactivate moving objects that are going slow enough for a long enough period of time. When the spheres reach the top of their arc they are moving slowly so they are candidates for deactivation. You can change the threshold velocities (linear and angular) at which objects are considered ...
by drleviathan
Wed May 13, 2015 4:44 am
Forum: General Bullet Physics Support and Feedback
Topic: Does anyone now how to use btCompoundShape???!!! ( HELP )
Replies: 4
Views: 3135

Re: Does anyone now how to use btCompoundShape???!!! ( HELP

So... what's the error?

Is it a compile error? a link error? or a runtime error?
by drleviathan
Tue May 12, 2015 12:17 pm
Forum: General Bullet Physics Support and Feedback
Topic: Collision filter mask works ugly
Replies: 4
Views: 7224

Re: Collision filter mask works ugly

He means that if you write 10 in 16-bit binary you get: 0000 0000 0000 1010. What matters is that two bits are set: the second bit from right, which represents the value 2, and the fourth bit from right, which represents the value 8 -- add them together and you get 10. Similarly 25 would look like: ...
by drleviathan
Mon May 11, 2015 2:38 am
Forum: General Bullet Physics Support and Feedback
Topic: Change position of a convex hull after creation
Replies: 5
Views: 5054

Re: Change position of a convex hull after creation

Do you want to change the transform of the body that uses the shape? If so, then you can just use btCollisionBody::setWorldTransform(). Or do you need to change the local transform of the btConvexHullShape itself? If this is the case then there are two ways to do it: (1) Create an entirely new shape...
by drleviathan
Sun May 10, 2015 5:02 pm
Forum: General Bullet Physics Support and Feedback
Topic: How to get btShape volume?
Replies: 3
Views: 4023

Re: How to get btShape volume?

I have some code that can compute the volume, center of mass, and inertia tensor of closed meshes and I've been looking for an excuse to clean it up and submit for public use. I'll try to get around to it, but I don't think I can get to it today.
by drleviathan
Thu May 07, 2015 3:18 pm
Forum: General Bullet Physics Support and Feedback
Topic: [Solved] raycasting bullet vehicle
Replies: 8
Views: 9239

Re: Does anyone now how to use btConvexHullShape???!!! ( HEL

Yes sorry, that was a typo. Use dynamicsEngine->addRigidBody(body);
by drleviathan
Wed May 06, 2015 11:21 pm
Forum: General Bullet Physics Support and Feedback
Topic: [Solved] raycasting bullet vehicle
Replies: 8
Views: 9239

Re: Does anyone now how to use btConvexHullShape???!!! ( HEL

To create a btConvexHull shape you would do something like this: int NUM_POINTS = 5; btVector3 points[NUM_POINTS] = { btVector3(-0.5, 1, 1), btVector3(-0.5, 1, -1), btVector3(-0.5,-1, 1), btVector3(-0.5,-1, -1), btVector3( 1, 0, 0) }; btConvexHullShape* shape = new btConvexHullShape(); for (int i = ...
by drleviathan
Mon May 04, 2015 5:26 pm
Forum: General Bullet Physics Support and Feedback
Topic: Contact forces in Bullet
Replies: 7
Views: 8832

Re: Contact forces in Bullet

I don't think Bullet would be a good choice for analyzing forces between touching objects. You'll probably need to use a different physics engine (probably a soft-body simulation). Does your simulation need to be real-time or can your simulation at offline speeds? A real-time game physics engine oft...
by drleviathan
Sun Apr 26, 2015 3:03 pm
Forum: General Bullet Physics Support and Feedback
Topic: A bullet in Bullet, ray test missing hits
Replies: 2
Views: 3585

Re: A bullet in Bullet, ray test missing hits

It sounds like you want to use Continuous Collision Detection (CCD). You should look at the ContinuousConvexCollision Demo or maybe read this wiki page/FAQ.
by drleviathan
Sun Apr 26, 2015 2:48 pm
Forum: General Bullet Physics Support and Feedback
Topic: Collision counter in bullet physics
Replies: 1
Views: 2817

Re: Collision counter in bullet physics

Bullet doesn't provide a system to generate collision events between objects -- you have to write your own. If you search these forums or other pages you might find examples that people have provided. Here is a modified system that I pulled out of a project I'm working on, which itself was based on ...
by drleviathan
Fri Apr 24, 2015 2:49 pm
Forum: General Bullet Physics Support and Feedback
Topic: How can I rotate an object's velocity?
Replies: 3
Views: 3889

Re: How can I rotate an object's velocity?

I believe it is safe to change the velocity of an object directly, despite its collisions. Within reason, of course -- setting the velocity very high or pushing the object deeper into penetration can only cause problems.
by drleviathan
Fri Apr 24, 2015 4:18 am
Forum: General Bullet Physics Support and Feedback
Topic: Getting surface normal from manifold
Replies: 1
Views: 2610

Re: Getting surface normal from manifold

My experience has been that btManifoldPoint::m_normalWorldOnB is pretty accurate as to the surface normal of the contact so I would expect it to be usable for most applications. Meanwhile the btSingleRayCallback method should also work in theory. You would test a ray against the other collision obje...