Real-Time Physics Simulation Forum 2006-12-04T16:02:02+00:00 https://pybullet.org/Bullet/phpBB3/app.php/feed/topic/761 2006-12-04T16:02:02+00:00 2006-12-04T16:02:02+00:00 https://pybullet.org/Bullet/phpBB3/viewtopic.php?p=2689#p2689 <![CDATA[Bullet 2.38 release: btNearCallback]]>
Similar to Open Dynamics Engine, Bullet 2.38 provides the option of a collision detection nearCallback. Main differences with ODE are:
- unlike ODE, this is optional: by default Bullet uses its built-in defaultNearCallback
- continuous collision detection (time of impact) next to discrete
- contact points are persistent and incrementally added/removed/maintained

See example in CcdPhysicsDemo how to register your own custom nearCallback. This can be useful to have more control over the collision detection pipeline:

Code: 

//by default, Bullet will use its own nearcallback, but you can override it using dispatcher->setNearCallback()void customNearCallback(btBroadphasePair& collisionPair, btCollisionDispatcher& dispatcher, btDispatcherInfo& dispatchInfo){btCollisionObject* colObj0 = (btCollisionObject*)collisionPair.m_pProxy0->m_clientObject;btCollisionObject* colObj1 = (btCollisionObject*)collisionPair.m_pProxy1->m_clientObject;if (dispatcher.needsCollision(colObj0,colObj1)){//dispatcher will keep algorithms persistent in the collision pairif (!collisionPair.m_algorithm){collisionPair.m_algorithm = dispatcher.findAlgorithm(colObj0,colObj1);}if (collisionPair.m_algorithm){btManifoldResult contactPointResult(colObj0,colObj1);if (dispatchInfo.m_dispatchFunc == btDispatcherInfo::DISPATCH_DISCRETE){//discrete collision detection querycollisionPair.m_algorithm->processCollision(colObj0,colObj1,dispatchInfo,&contactPointResult);} else{//continuous collision detection query, time of impact (toi)float toi = collisionPair.m_algorithm->calculateTimeOfImpact(colObj0,colObj1,dispatchInfo,&contactPointResult);if (dispatchInfo.m_timeOfImpact > toi)dispatchInfo.m_timeOfImpact = toi;}}}}
Other additions toBullet 2.38:

- an optional angularFactor scalar in btRigidBody, which allows to diminish/completely remove angular impulses. This can be handy for character control and cars. When you hit a wall, it won't fully get the rotational impact.
- bool btRigidBody::isInWorld(), which returns true is the btRigidBody is currently in a btCollisionWorld/btDynamicsWorld derived class.

Download at http://www.continuousphysics.com/mediaw ... e=Download
Enjoy!
Erwin

Statistics: Posted by Erwin Coumans — Mon Dec 04, 2006 4:02 pm

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