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I can control the length of a Gazebo step size through the world's SDF. Example with max_step_size=4 ms :

<physics name="4ms" type="ode">
            <max_step_size>0.004</max_step_size>
            <real_time_factor>-1.0</real_time_factor>
            <real_time_update_rate>250</real_time_update_rate>
</physics>

But, can I also set this value through an API call ?

Another simulation parameter, the Update rate, can be controlled through the .SDF or programmatically with a call to gz::sim::ServerConfig::SetUpdateRate. Example:

// Object to pass custom configuration to the server
gz::sim::ServerConfig serverConfig;

// Populate with some configuration, for example, the SDF file to load
serverConfig.SetSdfFile(config["world_sdf_path"].as<std::string>());
serverConfig.SetUpdateRate(update_rate); // in Hz

I would like to do the same for max_step_size.

Note 1: Gazebo's SimulationRunner seem to have this capability (see this method), but I don't know how to access it from a "user" point of view.

Note 2: Transfer from unanswered answers.gazebosim question

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  • $\begingroup$ Can you give more background info why you want to do this? I.e. what you want to achieve by changing this programmatically? $\endgroup$
    – JRTG
    Jul 1, 2023 at 16:43
  • $\begingroup$ I do co-simulation with another simulator (namely ns-3, a network simulator), so I need to control the execution steps of Gazebo finely. I chose to keep a fixed step_size during the whole simulation. The user edit a global configuration file and has the ability to define max_step_size. For now, I have to inject the user choice in the .sdf file, but this is ugly XML editing, which is less elegant than an API call. The way REAL_TIME_update_rate can be changed is way more convenient and readable, but clearly this is just for comfort as it still can be done with xml editing. $\endgroup$ Jul 3, 2023 at 8:11

1 Answer 1

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The set_physics service is able to set the max_step_size using a gz::msgs::Physics. I don't see a tutorial for this, but some code from the user_commands integration test can be used as a reference:

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    $\begingroup$ Worked like a charm. Thank you for the pointer ! $\endgroup$ Jul 12, 2023 at 17:01

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