Search found 827 matches

by drleviathan
Mon Feb 06, 2023 3:56 pm
Forum: General Bullet Physics Support and Feedback
Topic: No performance difference between static and kinematic bodies?
Replies: 3
Views: 134

Re: No performance difference between static and kinematic bodies?

The broadphase keeps track of the AABBs and also overlapping AABB pairs between distinct objects that might need narrowphase collision check to compute the contact points (if any). Ignoring narrowphase costs... there is overhead in: (1) knowing all the AABBs and overlaps and (2) adding new AABBs to ...
by drleviathan
Sun Feb 05, 2023 7:07 am
Forum: General Bullet Physics Support and Feedback
Topic: No performance difference between static and kinematic bodies?
Replies: 3
Views: 134

Re: No performance difference between static and kinematic bodies?

If the kinematic objects are not active then they are not much more expensive than static. If you were to bounce a dynamic object around the kinematic objects then they would activate, but since they are being "animated" by btDefaultMotionState which does nothing, then they will be deactiv...
by drleviathan
Thu Feb 02, 2023 4:47 pm
Forum: General Bullet Physics Support and Feedback
Topic: Reset/jump constraint to the initial position
Replies: 1
Views: 176

Re: Reset/jump constraint to the initial position

Let me repeat it back to you to make sure I understand: (1) You have two objects A and B connected by a constraint C . (2) You want to be able to reset the transforms of the two objects such that the constraint is satisfied (e.g. objects A and B are experiencing zero torque/force from the constraint...
by drleviathan
Sat Jan 21, 2023 6:17 am
Forum: General Bullet Physics Support and Feedback
Topic: extreme bouncing on btHeightfieldTerrainShape with small timesteps
Replies: 6
Views: 440

Re: extreme bouncing on btHeightfieldTerrainShape with small timesteps

When I look at the implementation of btAdjustInternalEdgeContacts() I see this: void btAdjustInternalEdgeContacts(btManifoldPoint& cp, const btCollisionObjectWrapper* colObj0Wrap, const btCollisionObjectWrapper* colObj1Wrap, int partId0, int index0, int normalAdjustFlags) { //btAssert(colObj0->g...
by drleviathan
Fri Jan 20, 2023 11:50 pm
Forum: General Bullet Physics Support and Feedback
Topic: extreme bouncing on btHeightfieldTerrainShape with small timesteps
Replies: 6
Views: 440

Re: extreme bouncing on btHeightfieldTerrainShape with small timesteps

I wonder if your problem isn't so much bad normals as it is interpenetration? This idea because I think the interpenetration resolution code can also introduce non-physical results that might look similar to glitches from bad normals. However, with such a small substep I doubt this could be the case...
by drleviathan
Fri Jan 20, 2023 7:31 pm
Forum: General Bullet Physics Support and Feedback
Topic: Is it possible to get the file of New FEM/Mass-spring deformable simulation?
Replies: 2
Views: 188

Re: Is it possible to get the file of New FEM/Mass-spring deformable simulation?

In the video description are links to python and C++ examples. Start by looking at the deformable pybullet examples in the code repository?

https://github.com/bulletphysics/bullet ... t/examples
by drleviathan
Fri Jan 20, 2023 7:25 pm
Forum: General Bullet Physics Support and Feedback
Topic: extreme bouncing on btHeightfieldTerrainShape with small timesteps
Replies: 6
Views: 440

Re: extreme bouncing on btHeightfieldTerrainShape with small timesteps

Is it really the edge normals? The sprung constraints between the fuselage and the wheels complicate matters. A quick way to verify it is caused by edge normals would be to have the box drag on a btStaticPlaneShape . If the problem goes away that would support the edge normals theory. Meanwhile, the...
by drleviathan
Wed Jan 18, 2023 7:16 am
Forum: General Bullet Physics Support and Feedback
Topic: How do I simulate falling dynamic objects?
Replies: 2
Views: 223

Re: How do I simulate falling dynamic objects?

You're using pybullet but are asking the forums focused on C++ and the core Bullet libraries. You might try asking in the pybullet section . The only ideas I have are: Is the object properly activated? You say you "move the box to the edge of the platform" before starting the simulation, b...
by drleviathan
Mon Jan 16, 2023 4:04 pm
Forum: General Bullet Physics Support and Feedback
Topic: Looking for help with settings and code to get my physics game correct
Replies: 3
Views: 306

Re: Looking for help with settings and code to get my physics game correct

I don't use ammo.js however after downloading the repository and scanning the codebase I learned: it appears to support set/getResitution().
by drleviathan
Thu Jan 12, 2023 4:25 pm
Forum: General Bullet Physics Support and Feedback
Topic: Looking for help with settings and code to get my physics game correct
Replies: 3
Views: 306

Re: Looking for help with settings and code to get my physics game correct

My advice is to avoid applying force/torque because it is complicated and difficult to tune. This because the amount of force depends on the mass and angular inertia of your object. Setting the velocities is the right way to go: it is much easier to implement because it works independently of mass a...
by drleviathan
Tue Jan 10, 2023 10:40 pm
Forum: General Bullet Physics Support and Feedback
Topic: Is it safe to retrieve objects transforms from one thread while stepSimulation is in other thread?
Replies: 1
Views: 221

Re: Is it safe to retrieve objects transforms from one thread while stepSimulation is in other thread?

Actually body->getWorldTransform() is not necessarily the best way to do it. When your render rate is NOT the same as your simulation step rate you can get aliased results from body->getWorldTransform() which can sometimes produce a visible jitter in the motion of otherwise smoothly moving objects. ...
by drleviathan
Fri Jan 06, 2023 4:45 pm
Forum: General Bullet Physics Support and Feedback
Topic: What are the units of force and mass and velocity?
Replies: 1
Views: 360

Re: What are the units of force and mass and velocity?

I believe the units of force are Newtons: kg * m / sec^2 because the simulation step expects the duration to be in seconds. You can always use different units by scaling the substep duration and then tweaking your own mass and distance units accordingly. This can sometimes be handy when your world a...
by drleviathan
Fri Jan 06, 2023 4:21 pm
Forum: General Bullet Physics Support and Feedback
Topic: compound shape / dynamic AABB tree question
Replies: 1
Views: 195

Re: compound shape / dynamic AABB tree question

Yes, the dynamic AABB tree helps, even for static compound shapes, especially for compound shapes with many child shapes. It is used in the narrowphase collision calculation to cull the number of contact point candidates. The only reason to NOT enable the dynamic AABB tree would be for a compound sh...
by drleviathan
Mon Oct 17, 2022 3:33 pm
Forum: General Bullet Physics Support and Feedback
Topic: [ammo] Problems with rigidity of sequential constraints
Replies: 2
Views: 525

Re: [ammo] Problems with rigidity of sequential constraints

Yes, I think you are right: large ratios between the mass/inertia of constrained objects are contributing to the error of the constraint solution. I believe the problem still reproduces in the latest version of Bullet, but I haven't tested constraints in a while. Your example is probably using the b...
by drleviathan
Tue Oct 11, 2022 3:51 pm
Forum: General Bullet Physics Support and Feedback
Topic: Correct way to simulate joint friction and joint damping
Replies: 1
Views: 432

Re: Correct way to simulate joint friction and joint damping

You're asking in the General Bullet Physics forum which is mostly about Bullet's core C++ library. You are more likely to get answers to your question if you ask in the PyBullet Support and Feedback forum.