Search found 4219 matches

by Erwin Coumans
Thu Sep 17, 2020 2:22 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Baraff/Witkin's integration matrix not positive: what to do?
Replies: 14
Views: 4117

Re: Baraff/Witkin's integration matrix not positive: what to do?

Finally, it took 11 years but it was worth waiting: a new paper by Theodore Kim addresses the problem, and one of the references points to this forum thread. See http://www.tkim.graphics/FEMBW or https://twitter.com/_TheodoreKim/status ... 0997393409
by Erwin Coumans
Thu Aug 20, 2020 3:03 am
Forum: PyBullet Support and Feedback
Topic: How does one lock rotation on one axis?
Replies: 1
Views: 554

Re: How does one lock rotation on one axis?

This forum is for PyBullet not panda.bullet
by Erwin Coumans
Thu Aug 20, 2020 3:02 am
Forum: PyBullet Support and Feedback
Topic: Simulate a rope for ball in the cup task
Replies: 1
Views: 575

Re: Simulate a rope for ball in the cup task

You can use maximal coordinates for the rope, it is likely more stable. (loadURDF(..., useMaximalCoordinates=True)
Or use deformable bodies, see https://github.com/bulletphysics/bullet ... _anchor.py
by Erwin Coumans
Thu Aug 20, 2020 3:00 am
Forum: PyBullet Support and Feedback
Topic: Using Z Axis down in the debug visualizer
Replies: 1
Views: 423

Re: Using Z Axis down in the debug visualizer

It is unfortunately not possible.
by Erwin Coumans
Thu Aug 20, 2020 2:59 am
Forum: PyBullet Support and Feedback
Topic: Read .bullet file to plot
Replies: 1
Views: 305

Re: Read .bullet file to plot

Try using https://github.com/bulletphysics/bullet3/tree/master/Extras/Serialize/ReadBulletSample or alternatively, save the joints using another mechanism, for example save manually or using startStateLogging, for example using STATE_LOGGING_MINITAUR (see the PyBullet Quickstart Guide) There are Pyt...
by Erwin Coumans
Wed Jul 08, 2020 5:02 pm
Forum: PyBullet Support and Feedback
Topic: HopperMuJoCoEnv
Replies: 1
Views: 372

Re: HopperMuJoCoEnv

PyBullet ships with HopperBulletEnv-v0, and other environments as listed here:

https://github.com/bulletphysics/bullet ... _init__.py

This forum is for PyBullet, if you want MuJoCo or Benelot's environments, try visiting another forum.
by Erwin Coumans
Wed Jul 08, 2020 12:05 am
Forum: PyBullet Support and Feedback
Topic: setJointMotorControl2 won't assign correct force value to certain joints
Replies: 5
Views: 961

Re: setJointMotorControl2 won't assign correct force value to certain joints

Don't enable 'realtime' simulation, but stepSimulation instead, when applying forces like this. Also, best to keep using a small time step (1./240. is default), not 1 second. Watch the various examples/gym environments, for example https://github.com/bulletphysics/bullet3/tree/master/examples/pybull...
by Erwin Coumans
Mon Jun 29, 2020 11:08 pm
Forum: PyBullet Support and Feedback
Topic: error: Not connected to physics server
Replies: 2
Views: 513

Re: error: Not connected to physics server

We don't support those envs. Please try using the envs included with pybullet_envs (after pip install pybullet --upgrade --user) HalfCheetahBulletEnv-v0 etc. Here is a list: https://github.com/pat-coady/trpo HumanoidDeepMimicBulletEnv-v1 CartPoleBulletEnv-v1 MinitaurBulletEnv-v0 MinitaurBulletDuckEn...
by Erwin Coumans
Fri Jun 19, 2020 4:09 pm
Forum: PyBullet Support and Feedback
Topic: [SOLVED in pybullet 2.8.2] Simple two-link URDF applyExternalForce unexpected response
Replies: 4
Views: 967

Re: Simple two-link URDF applyExternalForce unexpected response

Ah, I disabled the velocity/position motors by setting the force to zero. You can certainly leave the motors enabled, with a force of your choice to model joint friction or other effects such as springyness. I was assuming metric units (meter, seconds etc). If you are using different units, you need...
by Erwin Coumans
Fri Jun 19, 2020 3:48 am
Forum: PyBullet Support and Feedback
Topic: [SOLVED in pybullet 2.8.2] Simple two-link URDF applyExternalForce unexpected response
Replies: 4
Views: 967

Re: Simple two-link URDF applyExternalForce unexpected response

Thanks Avik, I had a look and found a few issues. One of them is in the applyExternalForce imlpementation, I fixed this now. https://github.com/bulletphysics/bullet3/pull/2870/commits/ebef331bbffb4631259648f5858a3a396dd3718a (it was a copy/paste bug, we never used applyExternalForce, since we always...
by Erwin Coumans
Tue Jun 16, 2020 5:54 pm
Forum: PyBullet Support and Feedback
Topic: JointMotor for urdf robot franka_panda
Replies: 1
Views: 667

Re: JointMotor for urdf robot franka_panda

It appears as if you are driving a strong motor against a joint limit, this won't work properly so try to avoid doing that.
by Erwin Coumans
Tue Jun 16, 2020 5:52 pm
Forum: PyBullet Support and Feedback
Topic: mecanum wheels
Replies: 1
Views: 688

Re: mecanum wheels

It is a challenging simulation problem. Make sure to 'unlock' the joint motors first, as usual.
(for each joint, setJointMotorControl2(obUid, linkIndex, p.VELOCITY_CONTROL, force=0 or close to 0).
I haven't created such robot yet, it may require a lot of effort to set this up properly.
by Erwin Coumans
Tue Jun 16, 2020 5:50 pm
Forum: PyBullet Support and Feedback
Topic: kuka reverse kinematic issue
Replies: 1
Views: 552

Re: kuka reverse kinematic issue

There are some inverse kinematics examples with Kuka, see https://github.com/bulletphysics/bullet ... ematics.py