Ignition Gazebo - Physics

Can someone help me understand how to add RayTrace to a system plugin?

I was reading through the documentation on the same at

From what I understood we need to implement the same as a custom feature as stated in this tutorial.
Custom Feature

But I do not need the implementation to be a plugin, instead I need to use the Raytrace in another system plugin.

Any help or hints on this will be appreciated.

Thank you.

Do ignition use Dartsim as the default physis engine?
When we load physics using
<plugin filename="ignition-gazebo-physics-system" name="ignition::gazebo::systems::Physics"> </plugin>

Is it loading the default Dartsim?