Real-Time Physics Simulation Forum

Just want to add some little things to drleviathan's great answer :- the inertia's eigenvectors align with the cardinal axes of the shape's local-frame ^ btMatrix3x3::diagonalized() will help about this. In fact, this is the only way to have a concave RigidBody that is dynamic or kinematic. There ar...

Yes, it supports.
See btCollisionObject::setUserPointer(void*) / getUserPointer.

+1 drleviathan :lol: I heard a rumor that btAxisSweep3 and bt32AxisSweep3 is faster than the generic one "with a limitation that it requires a fixed world size". It is in Sweep and Prune (SAP) in http://www.bulletphysics.org/mediawiki-1.5.8/index.php/Broadphase ^Edit: Erwin doesn't think s...

Thank drleviathan for the great detailed answer.
btPairCachingGhostObject is probably all I want (the 10-20 objects are all radar/sensor). I have never used ghost thingy before.

off-topic : It is lucky that this forum has you.

I have a loop like :- btDiscreteDynamicsWorld_instance->stepSimulation(......); //has 1000 bodies (20% CPU) add / change position of 10-20 btRigidbody; btDiscreteDynamicsWorld_instance->performDiscreteCollisionDetection(); //<-- slow (10% CPU) iterating btPersistentManifold for collision callback; T...

I couldn’t agree more. We need it now!

I totally encapsulated Bullet, and coded such functions myself.
It is not convenient, but it works.

getVelocity_relativeToCM_worldAxis(Vector3 positionRelativeToCM);
getVelocity_relativeToCM_shapeAxis(Vector3 positionRelativeToCM);
getVelocity_absolutePosition_worldAxis(Vector3 worldPosition);

Because no one answer ...

I am pretty sure that C++ Bullet is faster than its derivatives.

In practice, especially game, C++ itself is generally faster than python.
It is a reason that I lack knowledge to answer most of your questions.

Thank drleviathan. This is a very reasonable guess.

I am trying to encapsulate Bullet to my ECS game engine. After some test, I can simulate 2000 cubes, dropped randomly on a 2D static plane. Cubes rarely touch each other. With rendering + my engine cost, in PC, I get :- >80 fps in normal case 50 fps in the worst case (a brief period that all cubes s...

It is surprising that just scale every thing make so much difference in performance. :shock: First Experiment I created a scene with 1,000 cubes. Cube's size = 0.01f They scattered around a plane size = 5*5 (w*h) I got 20fps. The profile result states that Bullet Physics is the bottleneck. Second Ex...

I would like to know it too.

You may be interested in :-
- http://bulletphysics.org/Bullet/phpBB3/ ... php?t=9692.
- http://bulletphysics.org/Bullet/phpBB3/ ... php?t=4328
- http://www.bulletphysics.org/Bullet/php ... f=4&t=2794

As a reference, this is the page Anthrax11 mentioned (thank for editing it) :-
http://bulletphysics.org/mediawiki-1.5. ... om_scratch

It is a known limitation of Bullet. setLocalScaling is not a cure.

I agree with aviator : you have to manually swap the body.

I have created many bodies with equal mass + constraint like this :- http://i.imgur.com/aaWhPsw.png ^ Image shows 401 chunk of body. 400 bodies are constraint-ed with a single body at the center. All bodies has equal mass. When I change the hook position e.g. bulletFixedConstraint->getFrameOffsetA()...