Search found 4174 matches

by Erwin Coumans
Mon Mar 04, 2019 1:15 am
Forum: General Bullet Physics Support and Feedback
Topic: Friction problem - Sphere isnt rolling on a straight line.
Replies: 8
Views: 2417

Re: Friction problem - Sphere isnt rolling on a straight line.

OK, I got around implementing cone friction for rolling friction, so the two rolling friction directions are coupled and clamped against the friction cone together (instead of each rolling friction direction clamped against a friction pyramid).

https://github.com/bulletphysics/bullet3/pull/2138
by Erwin Coumans
Fri Mar 01, 2019 4:22 am
Forum: General Bullet Physics Support and Feedback
Topic: Friction problem - Sphere isnt rolling on a straight line.
Replies: 8
Views: 2417

Re: Friction problem - Sphere isnt rolling on a straight line.

Rolling friction indeed has an issue. We need to use cone friction for rolling friction (as we do for lateral friction). Will be fixed in a little while, see this issue: https://github.com/bulletphysics/bullet3/issues/2117 For now, disable rolling friction and manually apply some force (or use dampi...
by Erwin Coumans
Wed Feb 27, 2019 6:06 pm
Forum: PyBullet Support and Feedback
Topic: Spherical Joints
Replies: 10
Views: 1351

Re: Spherical Joints

This PR exposes the torques: https://github.com/bulletphysics/bullet3/pull/2130 Thanks for the report! By the way, the DeepMimic humanoid can be trained using stable PD control now: https://www.youtube.com/watch?v=aiWxIjtMMFI When switching to spherical joint motors, the policy doesn't train. See th...
by Erwin Coumans
Wed Feb 27, 2019 4:22 pm
Forum: PyBullet Support and Feedback
Topic: Pybullet not rendering correctly
Replies: 9
Views: 887

Re: Pybullet not rendering correctly

This is likely some Intel OpenGL driver issue
~~~~~~
Version = 3.3 INTEL-10.4.14
Vendor = Intel Inc.
Renderer = Intel HD Graphics 3000 OpenGL Engine
~~~~~~~
by Erwin Coumans
Wed Feb 27, 2019 4:19 pm
Forum: General Bullet Physics Support and Feedback
Topic: Can i help Bullet to resolve collisions
Replies: 2
Views: 313

Re: Can i help Bullet to resolve collisions

A few things to try: * use a smaller simulation step * increase the number of solver iterations * use a direct solver, Bullet provides Dantzig MLCP solver, see some of the examples in the ExampleBrowser * Use a btBoxShape for the ground * Enable SAT, separating axis test if you use btConvexHullShape...
by Erwin Coumans
Tue Feb 26, 2019 12:52 am
Forum: PyBullet Support and Feedback
Topic: Remove Collision from an entire MultiBody
Replies: 4
Views: 735

Re: Remove Collision from an entire MultiBody

Good to hear it is fixed!
by Erwin Coumans
Tue Feb 26, 2019 12:52 am
Forum: PyBullet Support and Feedback
Topic: Spherical Joints
Replies: 10
Views: 1351

Re: Spherical Joints

Spherical joints still need a bit more work indeed. I'll add the getJointStateMultiDof for spherical joints soon. setJointMotorControlMultiDof indeed sets the maxForce. It is not misnamed: if you set a target velocity of 0, the joint motor can model joint friction given the maximum (friction) force....
by Erwin Coumans
Tue Feb 26, 2019 12:44 am
Forum: PyBullet Support and Feedback
Topic: Pybullet not rendering correctly
Replies: 9
Views: 887

Re: Pybullet not rendering correctly

Do the regular Bullet examples work? For example, what do you see if you run
~~~~~~~
python3 -m pybullet_envs.examples.testBike
~~~~~~~
(its implementation is testBike.py)

I see this, on Mojave 10.14.3:

bike.png
bike.png (358.08 KiB) Viewed 843 times
When I run your script, it shows the R2D2 indeed, on the ground plane.
by Erwin Coumans
Fri Feb 22, 2019 7:45 pm
Forum: PyBullet Support and Feedback
Topic: Simulating closed loop structure in PyBullet
Replies: 1
Views: 279

Re: Simulating closed loop structure in PyBullet

SDF and URDF files need to be tree structure/ open loop. PyBullet provides user constraints to close loops. See our Minitaur example how to add such constraint. https://github.com/bulletphysics/bullet3/blob/master/examples/pybullet/gym/pybullet_envs/minitaur/envs/minitaur.py#L391 See createConstrain...
by Erwin Coumans
Tue Feb 19, 2019 12:18 am
Forum: PyBullet Support and Feedback
Topic: Remove Collision from an entire MultiBody
Replies: 4
Views: 735

Re: Remove Collision from an entire MultiBody

PyBullet. setCollisionFilterGroupMask should be fixed in latest repository. Thanks for the report.

Note that link index -1 refers to the base, and link index >=0 refers to child links.
https://github.com/bulletphysics/bullet3/pull/2116
by Erwin Coumans
Tue Feb 19, 2019 12:08 am
Forum: PyBullet Support and Feedback
Topic: Undesired behaviour when dropping cube
Replies: 1
Views: 238

Re: Undesired behaviour when dropping cube

Yes, by default PyBullet adds some damping for stability. You can disable it like this: p.changeDynamics(boxId,-1,linearDamping=0, angularDamping=0) In addition, there is a maximum velocity of 100 units (m/s for linear velocity and radians/sec for angular velocity). If this is an issue, you can comp...
by Erwin Coumans
Fri Feb 15, 2019 6:24 pm
Forum: General Bullet Physics Support and Feedback
Topic: btMultiBodyJointMotor interaction and control problem.
Replies: 3
Views: 506

Re: btMultiBodyJointMotor interaction and control problem.

Can you please file an issue in the tracker, with a C++ reproduction case and/or PyBullet reproduction case (PyBullet is preferable).

https://github.com/bulletphysics/bullet3/issues

Thanks!
Erwin
by Erwin Coumans
Mon Feb 11, 2019 4:52 am
Forum: General Bullet Physics Support and Feedback
Topic: Is there SAT algorithm in Bullet Physics Engine
Replies: 2
Views: 438

Re: Is there SAT algorithm in Bullet Physics Engine

Yes, Bullet provides a SAT implementation. You need to call the convexHull->initializePolyhedralFeatures(), this will create edges/trangles for a point cloud. convex hull generation is then enable SAT using getDispatchInfo().m_enableSatConvex=true; Implementation is in src\BulletCollision\CollisionD...
by Erwin Coumans
Tue Jan 15, 2019 5:40 pm
Forum: General Bullet Physics Support and Feedback
Topic: C API, how to get body position/orientation by id (URDF)
Replies: 2
Views: 429

Re: C API, how to get body position/orientation by id (URDF)

It is easiest to look into the PyBullet documentation and how it uses the C API in pybullet.c or use/enhance the BulletRobotics C++ wrapper on top of the C API. @mnaveau, this is example code, so you are supposed to copy it into your own project, if you want to use it. See also BulletRobotics target...
by Erwin Coumans
Tue Jan 15, 2019 4:58 pm
Forum: General Bullet Physics Support and Feedback
Topic: why are importers in the examples directory?
Replies: 4
Views: 893

Re: why are importers in the examples directory?

Good point. Python bindings and URDF import is not really part of the core SDK and it has been under heavy development. Our primary users are using Python nowadays, so the Python API is where the focus is at the moment. At some state, I'll move the files into a final 'BulletRobotics' library under '...