Real-Time Physics Simulation Forum

Re: Collision Resolution

2018-01-26T16:36:09+00:00

I am completely stumped here, I looked around HopperBulletEnv, and its dependencies, but couldn't find anywhere how in those environments constraints were defined to allow motion in 2D.

Code:

import timeimport pybullet as pp.connect(p.GUI)SURFACE = p.loadURDF("surface.urdf", useFixedBase=True)c = 0.51 # z distance between center of mass of CUBE and SURFACE when CUBE is on top of SURFACECUBE = p.loadURDF("cube.urdf", [0, 0, c])CONSTRAINT_1 = p.createConstraint(    SURFACE, -1, CUBE, -1, jointType=p.JOINT_PRISMATIC, jointAxis=[0, 1, 0], [0, 0, c], [0, 0, 0])CONSTRAINT_2 = p.createConstraint(    SURFACE, -1, CUBE, -1,  jointType=p.JOINT_PRISMATIC, jointAxis=[1, 0, 0], [0, 0, c], [0, 0, 0])while True:    p.stepSimulation()    POS, _ = p.getBasePositionAndOrientation(CUBE)    time.sleep(0.01)

Obviously, the reason this cannot work is because the two constraints contradict each other. JOINT_PRISMATIC prevents the motion in any but one dimension, and there are no jointType variables that allow for planar movements.

Statistics: Posted by ardabbour — Fri Jan 26, 2018 4:36 pm

Re: Collision Resolution

2018-01-25T06:02:28+00:00

There are a few ways to keep simulation in 2D indeed: you can use a 'fixed' base and add joints that allow motion in 2D. Look at the Gym environments 'Hopper' and 'HalfCheetah' and 'Walker2D', they only move in the 2D plane.

https://github.com/bulletphysics/bullet ... 2017may.py

Statistics: Posted by Erwin Coumans — Thu Jan 25, 2018 6:02 am

Collision Resolution

2018-01-23T09:41:35+00:00

An automatic collision resolution takes place when we step the simulation and 2 or more objects are in collision. Can we confine this resolution to 2D? That is, if 2 objects are in collision, they should be moved out of each other by applying forces to 2 axes out of 3. Is there such a way to do this?

Also, where can I read more about this collision resolution algorithm? Source code, a paper, raw mathematics or even a blog post would be great!

Statistics: Posted by ardabbour — Tue Jan 23, 2018 9:41 am