webots | Webots Robot Simulator

You should use some image processing library, like OpenCV, to process the camera image and recognize whether a cross or a circle was drawn in a certain square. Using different colors for crosses and circles may also help the image processing to categorize these items efficiently.

Take a look at this C example and you will understand how to access all the LEDs of the Thymio-II in Python:

When you have multiple FROM commands, you're not "inheriting" both of their contents into the same image - you're doing a multi-stage build. This allows you to COPY from that stage specifying the --from option. By default, the last stage in your Dockerfile will be the target (so, in your example, you're only actually using the ros2 image. The webots image is not actually being used there.

You have two options here:

1. Copy just the files you need from the webots image using COPY --from=base

This will probably be hard and finicky. You'll need to copy all dependencies; and if they're acquired through your package manager (apt-get), you'll leave dpkg's local database inconsistent.

1. Copy one of the Dockerfiles and change their FROM

This will probably work fine as long as they both use the same base distribution. You can go into one of the project's repositories and grab their Dockerfile, rebuilding it from the other image - just change, for example, cyberbotics/webots:R2021a-ubuntu20.04's Dockerfile to have FROM niurover/ros2_foxy:latest. It may require tinkering with the other commands there, though.

There are different possibilities to achieve what you want. A simple one would be to introduce a time counter variable (you may need to adjust the 100 and 200 values depending on your TIME_STEP):

I was able to solve this by setting the absolute path, shown in the image link, to a valid version of Python 3 in the Webots->Preferences command field. I had a slight error with NumPy not coming with this version but was easily fixable by doing -m pip install NumPy

I hope this is helpful to others as it was the last thing I tried and cost me some time.

Webots preferences screenshot example

It could be caused by several things:

• graphics card: Some old Intel graphics cards are not supported by Webots and may cause this kind of crash.
• graphics card driver: outdated drivers may cause such crashes. You should check that your graphics card driver is up-to-date.
• conflicting software: some third party software install some DLL in the Windows system32 folder (which is a bad practice) causing some conflicts with Webots if the DLL name is the same as some DLL used by Webots.
• your installation of Webots was somehow corrupted.

This should be a question of setting your environment variable(s) PATH (and possibly LD_LIBRARY_PATH) to the correct values. If you install SUMO via the package manager of your Linux (apt or something) there should be nothing to adapt. I see from the Webots docs that they recommend manual adaption of those paths. If you don't do those changes or revert them you should be always using the netedit coming with plain SUMO. If you want to use the Webots version adapt the paths such that they list Webots directories first.

Here are some documentation about how to use external library with Webots controllers: https://cyberbotics.com/doc/guide/using-webots-makefiles?tab-language=ros#adding-an-external-library-ccp

You can also find an example of integration of OpenCV (not version 4.30 but you can for sure take inspiration) in a Webots controller here: https://github.com/cyberbotics/webots/tree/master/projects/samples/howto/controllers/vision

I would use a Connector node to connect the end of the rope to the second robot stick.