Tutorials/1.5/make world/modify


 * 1) Tutorial: Modifying a World#

This tutorial describes how to modify global properties including scene and physics properties.

Start gazebo:

gazebo


 * 1) Scene Properties##

In the `World` tab, select the `scene` item. A list of scene properties will be displayed in the list box below. Click the triangle to expand the properties.



These properties allow you to change the ambient light. Note: The background color will not change if the Sky is enabled.


 * 1) Physics Properties##

In the `World` tab, select the `physics` item. A list of physics properties will be displayed in the list box below.

The `enable physics` check-box can be used to disable physics while allowing plugins and sensors to continue running.

The `update rate` parameter specifies in Hz the number of physics updates that will be attempted per second. If this number is set to zero, it will run as fast as it can. Note that the product of `update rate` and `step size` represents the target `real time factor`, or ratio of simulation time to real-time.

The `gravity` parameter sets the global gravity vector components in m/s^2.

In the solver block, the `step size` specifies the time duration in seconds of each physics update step. The `iterations` parameter specifies the number of iterations to use for iterative LCP solvers (used by ODE and bullet). The `SOR` parameter stands for successive over-relaxation, which can be used to try to speed the convergence of the iterative method.

The constraints block contains several parameters related to solving constraints. The `CFM` and `ERP` parameters stands for Constraint Force Mixing and Error Reduction Parameter and are used by ODE and bullet. The CFM and ERP parameters can be related to linear stiffness and damping coefficients. The `max velocity` and `surface layer` parameters are used to resolve contacts with a split impulse method. Any contacts with that penetrate deeper than a depth specified by `surface layer` and have a normal velocity less than `max velocity` will not bounce.

See the sdf physics documentation for a description of these parameters.




 * 1) Next

Next: Programmatic World Control