Hi,

I am working on a the Plankton project where some links are expected to be available in Gazebo because some custom sensor plugins are attached to them. This is inherited from UUV simulator in ROS 1. The historical way to do that is to have a 0-bounded revolute joint between the baselink and the sensor links. I understand that it increases the simulation burden. A secondary drawback is that using such joints makes it mandatory to publish their 0-value for other nodes such as *robotstate_publisher*, even on the real robot (that is just more boilerplate code we prefer not to have at all).

I have only recently discovered that it is possible to forward fixed joints to Gazebo:

<joint name="imu" type="fixed"> ... </joint>
<gazebo reference="imu">
    <preserveFixedJoint>true</preserveFixedJoint>
</gazebo>

It seems to work (the joint does not exist in model->GetJoints()), but I want to make sure that it indeed lightens the computation load of Gazebo.

If this is the case I'll confirm to other team members that it should be the new practice.