Search found 4097 matches

by Erwin Coumans
Thu Aug 16, 2018 5:12 pm
Forum: General Bullet Physics Support and Feedback
Topic: Precision of getClosestPoints calculation ?
Replies: 2
Views: 93

Re: Precision of getClosestPoints calculation ?

Using an extremely small margin and changing the setEqualVertexThreshold is not supported. Also, make sure to use the double precision version. Also, I made some fix in the btGjkPairDetector.cpp related to degenerate cases here. You may want to share a small reproduction case based on a modified exa...
by Erwin Coumans
Mon Jul 09, 2018 7:27 am
Forum: General Bullet Physics Support and Feedback
Topic: When building URDF models, which visualizer do you use?
Replies: 3
Views: 236

Re: When building URDF models, which visualizer do you use?

Well, we use PyBullet for that, is can visualize URDF, SDF and MJCF etc. Also, it has utilities to show inertial boxes and in wireframe mode it can show joint axis etc.

You can see a few screenshots in the PyBullet Quickstart Guide.
by Erwin Coumans
Thu Jun 14, 2018 6:48 pm
Forum: PyBullet Support and Feedback
Topic: How well suited is PyBullet to Domain Randomization for Sim-to-Real?
Replies: 1
Views: 199

Re: How well suited is PyBullet to Domain Randomization for Sim-to-Real?

Various projects inside Google use PyBullet with domain randomization, there are plenty of PyBullet Python APIs to change dynamics and visuals. Aside from PyBullet APIs, you can also use the UrdfEditor to modify any URDF setting (link sizes, joint pivot location etc). >> PyBullet to handle texture r...
by Erwin Coumans
Wed Jun 06, 2018 3:49 pm
Forum: PyBullet Support and Feedback
Topic: Position control for robot base?
Replies: 4
Views: 355

Re: Position control for robot base?

Indeed, you should not call resetBasePositionAndOrientation during the simulation, since it is an abrupt change that ignore and violates all dynamics, and likely give bad simulations and artifacts. If you reset the simulation (right after loading the URDF file or when teleporting a robot back to its...
by Erwin Coumans
Wed May 09, 2018 12:54 am
Forum: General Bullet Physics Support and Feedback
Topic: stepSimulation freezes for large number of multi body objects.
Replies: 2
Views: 292

Re: stepSimulation freezes for large number of multi body objects.

Is this C++ or PyBullet? You should be able to profile timings and gradually increase the number of robots.

We are not clearvoyant: try to file an issue in the tracker and provide a simple reproduction case.

https://github.com/bulletphysics/bullet3/issues
by Erwin Coumans
Thu May 03, 2018 2:56 pm
Forum: General Bullet Physics Support and Feedback
Topic: CPU multithreading is working!
Replies: 145
Views: 45102

Re: CPU multithreading is working!

Thanks for the reply. Can you report the issue in the Bullet https://github.com/bulletphysics/bullet3/issues tracker, so we can track progress on fixes? 1. My program using single-threaded btDiscreteDynamicsWorld crashed because of btSequentialImpulseConstraintSolver::getOrInitSolverBody method retu...
by Erwin Coumans
Thu May 03, 2018 2:52 pm
Forum: General Bullet Physics Support and Feedback
Topic: Maximum angular velocity
Replies: 2
Views: 222

Re: Maximum angular velocity

You can override the maximum angular velocity using btMultiBody::setMaxCoordinateVelocity

This maximum velocity is a safety mechanism, to avoid energies going to infinity.

What are you trying to achieve with a very high velocity?
by Erwin Coumans
Thu May 03, 2018 1:38 pm
Forum: General Bullet Physics Support and Feedback
Topic: Is diagonlize/extractRotation broken, i.e., does nothing? see 3 lines of example code and try yourself
Replies: 3
Views: 203

Re: Is diagonlize/extractRotation broken, i.e., does nothing? see 3 lines of example code and try yourself

The original btMatrix3x3::diagonalize method should work for symmetric matrices. Recently (2017) I replaced it with a diagonalize method based on the "A Robust Method to Extract the Rotational Part of Deformations" paper and its extractRotation implementation, but the resulting rotation still includ...
by Erwin Coumans
Thu May 03, 2018 1:26 pm
Forum: General Bullet Physics Support and Feedback
Topic: Someone familiar with btMultiBody please let me know if this is correct.
Replies: 2
Views: 287

Re: Someone familiar with btMultiBody please let me know if this is correct.

I strongly recommend first using the PyBullet Python bindings, and loading URDF or SDF files, it is documented in the https://docs.google.com/document/d/10sXEhzFRSnvFcl3XxNGhnD4N2SedqwdAvK3dsihxVUA/edit#heading=h.2ye70wns7io3 . Our recent RSS paper (Sim-to-Real: Learning Agile Locomotion For Quadrup...
by Erwin Coumans
Wed Apr 11, 2018 7:14 am
Forum: PyBullet Support and Feedback
Topic: pyBullet vs Gazebo
Replies: 3
Views: 706

Re: pyBullet vs Gazebo

Ultimately you can try out both and decide for yourself. It seems that Gazebo uses Bullet Gazebo uses btRigidBody from Bullet (maximal coordinate rigid bodies) which is not necessary the best way for robotics, it allows for joint gap. PyBullet uses Featherstone articulated rigid bodies (btMultiBody)...
by Erwin Coumans
Thu Mar 15, 2018 3:00 pm
Forum: General Bullet Physics Support and Feedback
Topic: [SOLVED] Updating CollisionShape leads to undetected collisions
Replies: 2
Views: 294

Re: [SOLVED] Updating CollisionShape leads to undetected collisions

Halfextents needs to be positive values (and sphere radius too etc). Negative mass is also not supported.

In addition, if you make changes to collision shape, you first need to

1) remove the rigid body/collision object from the world,
2) make the changes
3) re-insert the body to the world.
by Erwin Coumans
Thu Mar 01, 2018 10:07 pm
Forum: General Bullet Physics Support and Feedback
Topic: CPU multithreading is working!
Replies: 145
Views: 45102

Re: CPU multithreading is working!

Thanks, this is very interesting. Have you experimented with graph coloring (solving a large island in parallel)?
by Erwin Coumans
Wed Feb 07, 2018 3:57 am
Forum: PyBullet Support and Feedback
Topic: Geometry resolution importing from URDF
Replies: 1
Views: 341

Re: Geometry resolution importing from URDF

You can use the flags=pybullet.URDF_USE_IMPLICIT_CYLINDER in loadURDF, then it uses an implicit cylinder. Alternatively, just model a tesselated cylinder in Blender (or other 3d modeler) at the resolution you like, and write it to a wavefront OBJ file and use that.
by Erwin Coumans
Wed Feb 07, 2018 3:55 am
Forum: PyBullet Support and Feedback
Topic: JBullet Basic question
Replies: 9
Views: 870

Re: JBullet Basic question

Never heard about JBullet, what is it?

This is a forum for PyBullet, the Python module, which is much more than just Python bindings for Bullet: it also adds rendering, VR, inverse kinematics, inverse dynamics, rendering (CPU and OpenGL) etc. See the PyBullet quickstart guide.