9. Troubleshooting

November 2, 2023 · View on GitHub

9. Troubleshooting

This sections details some known configuration issues and how to solve them. Especially Rendering using OpenGL is prone to crash. When in doubt, please read all the sections. Sometimes the same cause can produce multiple error messages.

9.1. Pinocchio module

Unfortunately, two python packages both use the pinocchio name. We recommend using conda to install all the dependencies of our SimulationFramework:

conda install pinocchio

Alternatively, you can install it systemwide following the instructions at https://stack-of-tasks.github.io/pinocchio/download.html

Using pip will install the wrong package, causing this error!!

9.2. ERROR: GLEW initalization error: Missing GL version

When using mujoco you might encounter this error, when working with the virtual RGB-D cameras.

During setup you had to set the environmental variable LD_PRELOAD. To the best of our knowledge, this variable must be set when using "windowed" mode (render=HUMAN).
But this variable must not be set when using offscreen rendering (render=OFFSCREEN). As this will not use OpenGL Hardware rendering, this might be very slow and "blind" mode (skipping rendering with render=BLIND) might be preferred.

We currently suspect this is caused by an issue with NVidia-GPU drivers and is outside of our scope to fix.

9.3 numpy.ndarray size changed

This error occurs when there is a version mismatch with numpy. Please remove all numpy installations in both pip and conda:

conda uninstall numpy
pip uninstall numpy

Afterwards install numpy only with pip:

pip install --upgrade numpy

9.4 ImportError libOpenGL.so

In some instances after following the installation instructions, the mujoco demos might show this behavior and abort with an error:

Import error. Trying to rebuild mujoco_py.
running build_ext
building 'mujoco_py.cymj' extension
... (log output pruned) ...
ImportError: libOpenGL.so.0: cannot open shared object file: No such file or directory

In this case, OpenGL is missing. It can be installed with

sudo apt install libopengl0

9.5 Wayland does not work with GLFW

There is still lacking support for Wayland in GLFW. Switch to X11 or similar alternatives to run the simulation with graphical interface for MuJoCo.

9.6 Mujoco: Rendering / Camera issues

Mujoco OpenGL rendering is error prone. Try switching to Mujoco v2.0, which we find to be more stable.

9.7 Pybullet: Inhand Camera freeze

Pybullet Camera rendering can sometimes freeze the whole program execution. This reliably happens in a MultiBot Context, but the issue is the p.getCameraImage() call. Therefore we suspect that the issue is caused by Pybullet itself and not our implementation.