Real-Time Physics Simulation Forum 2022-09-12T13:58:45+00:00 https://pybullet.org/Bullet/phpBB3/app.php/feed/topic/13478 2022-09-12T13:58:45+00:00 2022-09-12T13:58:45+00:00 https://pybullet.org/Bullet/phpBB3/viewtopic.php?p=44117#p44117 <![CDATA[getContactPoints() returns wrong points positions]]> https://github.com/bulletphysics/bullet ... ntsBug.zip

Here the soft body cylinder is dropped on a plane located at height z=0. After cylinder reaches the plane, z-coordinate of the contact points must be around zero, definitely not z=1. Moreover, contact points in world coordinates for both the plane and cylinder must be approximately the same (z coordinate must not be reversed).
But I get the following tuple returned by the p.getContactPoints():
(0, 1, 0, -1, -1, (-2.759741412921471e-12, -2.26367090816533e-12, -1.0), (2.759741412921471e-12, 2.26367090816533e-12, 1.0), (2.759741412921471e-12, 2.26367090816533e-12, 1.0), -0.000944430001919847, 1.0, 0.0, (0.0, 0.0, 0.0), 0.0, (0.0, 0.0, 0.0))
Look at the contact points and normals, they are completely wrong (probably swapped?): p.getContactPoints() returns contact points coordinates with z=1

It seems that I get the normals instead of the contact points(z). Moreover, number of contact points is too large.

Code: 

import pybullet as pDEBUG_CAMERA_YAW = 0.0DEBUG_CAMERA_PITCH = -20.0DEBUG_CAMERA_DISTANCE = 0.3p.connect(p.GUI)# p.connect(p.DIRECT)p.setRealTimeSimulation(0)  # 240 fpsp.setPhysicsEngineParameter(enableFileCaching=0)p.resetSimulation(p.RESET_USE_DEFORMABLE_WORLD)p.setGravity(0, 0, -9.8)p.resetDebugVisualizerCamera(cameraDistance=DEBUG_CAMERA_DISTANCE,                             cameraYaw=DEBUG_CAMERA_YAW,                             cameraPitch=DEBUG_CAMERA_PITCH,                             cameraTargetPosition=[0, 0, 0.15])E = 400# nu = 0...0.5, poisson ratio# nu =  0.45nu = 0.45nh_lamda = E*nu/(1+nu)/(1-2*nu)nh_mu = E/2/(1+nu)plane_id = p.loadURDF("plane.urdf",                      basePosition=[0, 0, 0],                      useFixedBase=1)cylinder_id: int = p.loadSoftBody("cylinder.vtk",                                  basePosition=[0, 0, 0.1],                                  baseOrientation=[0, 0, 0, 1],                                  simFileName="cylinder.vtk",                                  mass=0.02,                                  scale=1.0,                                  useNeoHookean=1,                                  NeoHookeanMu=nh_mu,                                  NeoHookeanLambda=nh_lamda,                                  NeoHookeanDamping=0.05,                                  collisionMargin=0.0005,                                  useSelfCollision=0,                                  frictionCoeff=0.05,                                  repulsionStiffness=100)for _ in range(320):    p.stepSimulation()    contact_points = p.getContactPoints()    if len(contact_points) > 0:        print(contact_points[0])        break
M1 MacBook Pro, pybullet==3.2.5, numpy==1.23.2

Statistics: Posted by renatyv — Mon Sep 12, 2022 1:58 pm

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