Parsing Error with URDF

[chris0914]

Hi everyone,

I already mentioned this error in #2730 and reproduced it, more or less on accident, with pybullet. In the before mentioned Issue I loaded the 'turtlebot.urdf' file within an QtProject and all the elements of the robot were parsed on the same spot, using the C++ API.

However this time I used pybullet and opened a matplotlib plot before launching the simulation. Below is a MWE to reproduce. The placement in general works, as the cylinder is placed correctly. I reproduced this on one other computer. Both running on Ubuntu 18.04 and I installed matplotlib/pybullet via pip3. The outcome depends on the used turtlebot.urdf file. When using the turtlebot.urdf from pybullet_robots a triangular shape appears, see image below.

#!/usr/bin/python3
import pybullet as p
import matplotlib.pyplot as plt
from time import sleep

if __name__ == '__main__':

    # Break turtlebot parser
    plt.plot([1,2,3])

    # Simulation initialization
    server_client = p.connect(p.GUI)
    p.resetSimulation()
    p.setRealTimeSimulation(False)
    p.setTimeStep(1./240.0)
    p.setGravity(0, 0, -9.81)

    # drop plane and turtlebot
    p.createMultiBody(0, p.createCollisionShape(p.GEOM_PLANE))
    p.createMultiBody(0, p.createCollisionShape(shapeType=p.GEOM_CYLINDER, radius=0.1, height=1.0, collisionFramePosition=[1.0, 1.0, 0.5]))
    turtle = p.loadURDF("data/turtlebot.urdf", [0, 0, 0], p.getQuaternionFromEuler([0, 0, 0]))

    sleep(10.0)

Any idea where to dig? Cheers Chris

[erwincoumans]

No idea, it looks normal here, running the same code: I'm sure it runs fine in an online Google Colab as well, likely some driver/GPU/Ubuntu installation issue.

[chris0914]

Hi Erwin,

thanks for the answer. I rebuild a fresh system for Ubuntu 18.04 and Ubuntu 20.04. Running under python3 both showed the same error. However, on the Ubuntu 20.04 system I installed python2.7 and surprisingly everything runs fine! So I tested that on my main setup, and indeed using python2.7 everything works fine again. Have you tested my code using python2 or python3?

Any idea? As I wouldn't want to go back to python2.

Cheers Chris

[erwincoumans]

Can't reproduce, and haven't heard a similar issue before. Perhaps a broken graphics driver? Closing for now.