Search found 57 matches
- Fri Sep 14, 2012 5:53 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Cloth collision detection-What is the currnt stateof the art
- Replies: 12
- Views: 22555
Re: Cloth collision detection-What is the currnt stateof the
Edge versus edge can actually be transformed to be similar to vertex versus face. In short, vertex versus face with linearly moving vertices is done by: Convert to vertex versus plane by determining the plane equation for the face Convert to origin versus plane by considering the problem relative to...
- Wed Sep 12, 2012 3:37 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Cloth collision detection-What is the currnt stateof the art
- Replies: 12
- Views: 22555
Re: Cloth collision detection-What is the currnt stateof the
I've been rewriting a lot of the Bullet softbody collision code redoing the vertex-face collision detection, adding edge-edge detection, supporting self-collision with the same, and sprinkling it with multithreading. Like the Brochu et al. paper I do the constant velocity approximation. I initially ...
- Tue Jun 12, 2012 6:36 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Resetting scene
- Replies: 3
- Views: 4938
Re: Resetting scene
As well as resetting the broadphase pool, I also clean out the overlapping pair cache: btOverlappingPairCache* pair_cache = m_dynamics_world->getBroadphase()->getOverlappingPairCache(); btBroadphasePairArray& pair_array = pair_cache->getOverlappingPairArray(); for(int i = 0; i < pair_array.size(...
- Fri May 18, 2012 7:16 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Bug Report with complete code to reproduce it
- Replies: 6
- Views: 7277
Re: Bug Report with complete code to reproduce it
If the bodies from planet 1 are never going to come into contact with plane 1 (or you don't care if they do), then indeed you do not need that plane. I assumed you were using the planes to confine the objects within their zones.
- Thu May 17, 2012 12:48 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Bug Report with complete code to reproduce it
- Replies: 6
- Views: 7277
Re: Bug Report with complete code to reproduce it
You could do it by using two planes at (0,500,0), one facing each way. Then use collision masks to exclude the plane the rigid body is expected to be inside of. O <- (rigid body on planet 2) ----------/\-------- <- plane 2 at 0, 500, 0 facing up -------\/----------- <- plane 1 at 0, 500, 0 facing do...
- Thu May 17, 2012 6:11 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Bug Report with complete code to reproduce it
- Replies: 6
- Views: 7277
Re: Bug Report with complete code to reproduce it
Planes have an inside and an outside, like they are infinitely thick. The normal of the plane points to the outside. So your vehicle is actually trapped deep inside the top plane, which is registered as a penetration which it then attempts to get out of. Flip your top plane body so that it points do...
- Tue May 15, 2012 1:20 am
- Forum: General Bullet Physics Support and Feedback
- Topic: btConvexHullShape reutilization
- Replies: 13
- Views: 11029
Re: btConvexHullShape reutilization
Maybe you have a mixup between an object index and a collision shape pointer? I see that for obtenerMatrizRigidBody() you use sim as an index into the object array, while in Java_com_contimita_utils_BulletNdk_insertarDynamicConShape() sim is a collision shape pointer. If the objects are actually app...
- Sat May 12, 2012 6:45 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Make btSoftBody more hard/rigid
- Replies: 2
- Views: 4956
Re: Make btSoftBody more hard/rigid
You could remove the bending links by iterating over all the links and looking for those that have the m_bbending value set. Or freeze them by modifying the linear stiffness of the bending link material to 1 and setting the rest length of the links to the current distance between the nodes, and unfr...
- Sat May 12, 2012 6:24 am
- Forum: General Bullet Physics Support and Feedback
- Topic: btConvexHullShape reutilization
- Replies: 13
- Views: 11029
Re: btConvexHullShape reutilization
As long as the local scaling and margin of the convex hull shape remains the same, I see no reason why it shouldn't work.
- Sat May 12, 2012 6:02 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Bug in btRigidBody::applyImpulse's use of m_linearFactor?
- Replies: 3
- Views: 4323
Re: Bug in btRigidBody::applyImpulse's use of m_linearFactor
It does look like the code is a bit confused about whether the linear factor is a scale factor that is applied to the forces/impulses acting on the body, or only on that part that induces a linear motion. Usually the linear factor isn't changed from its default of (1,1,1), in which case it isn't an ...
- Mon Apr 09, 2012 7:38 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Meaning of softbody anchor hardness
- Replies: 0
- Views: 2992
Meaning of softbody anchor hardness
I'm investigating some issues with the softbody anchor solving. I think there is a bug in the formulae used, but I have some difficulty trying to understand what the intention behind the code is. I understand that setting anchor hardness (softbody->m_cfg.m_kAHR) to 1 means that the node is expected ...
- Wed Apr 04, 2012 7:21 am
- Forum: General Bullet Physics Support and Feedback
- Topic: 100m drop at 9.81m/s: tunneling through btHeightfieldTerrain
- Replies: 7
- Views: 8261
Re: 100m drop at 9.81m/s: tunneling through btHeightfieldTer
After dropping 100m the cylinders will be falling at a speed of about 44m/s. With a timestep of 1/120s, that's about 36cm per timestep. Any collisions between objects with a combined thickness less than that (including collision margins) are likely to be missed. The cylinders are 20cm, while the thi...
- Sat Jan 21, 2012 6:24 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Why is "solverConstraint.m_jacDiagABInv" updated again?
- Replies: 2
- Views: 4267
Re: Why is "solverConstraint.m_jacDiagABInv" updated again?
It's not updated again. They are two different sets of constraints. There are three sets of constraints involved: The contact constraints The friction constraints All other constraints (e.g. hinge, 6dof, point2point, etc.) The ones set up in solveGroupCacheFriendlySetup() are the constraints from th...
- Tue Jan 17, 2012 12:01 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Bullet 2.77 Restitution issue.
- Replies: 8
- Views: 11191
Re: Bullet 2.77 Restitution issue.
What is the exact definition of restitution in that code context? In that code snippet the restitution is the calculated desired speed after collision. In essence the current speed times the restitution factor set by colobj->setRestitution(). One could change the logic so that if the restitution fa...
- Tue Jan 17, 2012 6:09 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Bullet 2.77 Restitution issue.
- Replies: 8
- Views: 11191
Re: Bullet 2.77 Restitution issue.
As this issue persists in 2.78 and I believe 2.79 as well, and I'm having the same problem, I traced through it all and found the problem. It's in btSequentialImpulseConstraintSolver::setupContactConstraint(), particularly this part: btScalar positionalError = 0.f; btScalar velocityError = restituti...