Configure physics properties

[iche033]

Support configuring physics properties like max step size, real time update rate, gravity, etc (see Physics SDF DOM and perhaps also some of the fields in physics.proto) through ign gazebo components and/or ign-transport

Additionally a component inspector to let users edit these properties through the gui

[mrushyendra]

I made some initial changes here to add a component that allows users to change the step size or target rtf. While it works in practice, I was wondering where the best place to actually update the SimulationRunner's stepSize and desiredRtf properties would be. Currently I'm doing it in step here:

https://github.com/mrushyendra/ign-gazebo/blob/56f800e073db107120f924f196fcb92e818b38f6/src/SimulationRunner.cc#L740

but was wondering if that is the right approach. Thank you!

[ahcorde]

Hi @mrushyendra

Thank you for picking this issue. I think it would be great if you can create a PR because we can discuss better the code and see easily the new code.

I think you can also consider two more things:

• It would also be great to make the component inspector call those new topics to edit physics from the GUI.
• the PhysicCmd should probably be handled by the UserCommands system.

This PR #482 is adding light control, you can get some inspiration.

[luca-della-vedova]

I started to build on top of the work by @mrushyendra and should be ready to open a draft PR for component inspector control of physics parameters soon.