The time step used by controller [...] is not a multiple of WorldInfo.basicTimeStep!

[omichel]

I see this message in the Webots console when running my simulation. What does this mean?

[omichel]

Webots allows to specify the control step and the simulation step independently. The control step is the argument passed to the wb_robot_step function, it specifies the duration of a step of control of the robot. The simulation step is the value specified in WorldInfo.basicTimeStep field, it specifies the duration of a step of integration of the physics simulation, in other words: how often the objects motion must be recomputed. The execution of a simulation step is an atomic operation: it cannot be interrupted. Hence a sensor measurement or a motor actuation must take place between two simulation steps. For that reason the control step specified with each wb_robot_step function call must be a multiple of the simulation step. If it is not the case you get this error message. So, for example if the WorldInfo.basicTimeStep is 16 (ms), then the control step argument passed to the wb_robot_step function can be 16, 32, 48, 64, 80, 128, 1024, etc.

[cdrizzt]

Hello,

I have a couple of questions:

Question 1:
What happens if I set 'wb_robot_step' to a value smaller than WorldInfo.basicTimeStep?
For example: WorldInfo.basicTimeStep = 8, wb_robot_step(2)
I tested and found that it behaves the same as when WorldInfo.basicTimeStep = 8, wb_robot_step(8).

Question 2:
Is the execution time of wb_robot_step() related to real-world time?
I noticed that wb_robot_step() is generally consistent with real-world time. However, if I copy a large amount of data after wb_robot_step() and then call wb_robot_step() again, would it cause Webots time to lag behind real time?