Sojourner move through rocks

[DavidMansolino]

Describe the Bug The Sojourner moves through the rock as if it was not there:

[stefaniapedrazzi]

On Ubuntu 18.04 it works fine.

[omichel]

On Windows, it is very strange, I can reproduce this bug, but not systematically. I am trying to identify a reproducible procedure.

[omichel]

I could not find a way to reproduce the problem systematically, but with the following procedure it is likely (about 50%) to show the buggy behavior:

1. Open webots with projects/langauges/cpp/worlds/example.wbt
2. Go to the File menu, Open Sample World and select the sojourner.wbt world by double-clicking on it.
3. In about 50% of the cases, the robot passes through the first stone.
4. Resetting the simulation can show the bug again, systematically.
5. Reverting the simulation fixes the problem in 50% of the cases.

[stefaniapedrazzi]

With this procedure it is reproducible on Ubuntu too.

[omichel]

With this simple world file, I can reproduce a similar bug on Windows. In about one run out of 4 (you need to perform several reverts to see it), the ball is passing through the rock.

#VRML_SIM R2020b utf8
WorldInfo {
  coordinateSystem "NUE"
}
Viewpoint {
  orientation -0.8948797260489955 -0.4263143137077413 -0.13208475246739285 0.6620073677969002
  position 0.1867745168165805 0.49890843050016187 0.6135971533594632
}
Background {
  skyColor [
    0.15 0.45 1
  ]
}
DirectionalLight {
  ambientIntensity 1
  direction 0 -1 0
  castShadows TRUE
}
Rock10cm {
  translation 0.387314 -0.116121 -0.177911
  name "rock 10 cm(2)"
  color 0.9 0.4 0.3
}
Ball {
  translation 0.39 0.09716 -0.166909
}

[omichel]

It seems to be a regression as I cannot reproduce the bug on the master branch.