Change to std::get_if for gz::rendering::Variant for throwless behaviour

[dheerubhai-101]

🦟 Bug fix

Fixes #516

Summary

Use of std::get for gz::rendering::Variant throws exceptions whenever it is interpreted as the wrong type. Non-critical exceptions when working Gazebo can cause lead to cumbersome debugging. So the code has been changed to use std::get_if for a softer error handling when encountering wrong Variant type.

Two things have been changed

• Code using try catch with std::get changed to std::get_if in ogre/src/OgreThermalCamera.cc, ogre2/src/Ogre2BoundingBoxMaterialSwitcher.cc and ogre2/src/Ogre2SegmentationMaterialSwitcher.cc
• std::holds_alternative nested with std::get changed to use only std::get_if for simpler value access in ogre2/src/Ogre2GpuRays.cc and ogre2/src/Ogre2ThermalCamera.cc

The following tests FAILED:

         23 - INTEGRATION_gpu_rays_ogre_gl3plus (Failed)
         88 - REGRESSION_reload_engine_ogre2_gl3plus (Failed)
        216 - UNIT_RenderingIface_TEST_ogre2_gl3plus (Failed)

due to the bug pointed out by @j-rivero.
Reason: Error while loading the library [/gz_ws/install/lib/gz-rendering-9/engine-plugins/libgz-rendering-ogre2.so]: /gz_ws/install/lib/gz-rendering-9/engine-plugins/libgz-rendering-ogre2.so: undefined symbol: _ZThn944_N4Ogre7HlmsPbs19_changeRenderSystemEPNS_12RenderSystemE

Will need your help to test it properly.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[iche033]

looks good, just minor style comments

[iche033]

DCO failed. Can you sign your commits? Click on the button to the right of DCO check and select View details to see how to sign the commits

[dheerubhai-101]

hey Ian, I think while I was signing off the DCO, the commits of other contributors have also been included. Is there any way to resolve that? This is my first PR so I am quite unsure and I believe I messed up.

[ahcorde]

@dheerubhai-101 you closed the PR, are you planning to reopen it again ?

[dheerubhai-101]

@dheerubhai-101 you closed the PR, are you planning to reopen it again ?

Hi @ahcorde yes, I will reopen the PR today. The PR included the commits you made when I pulled and rebased, with my sign off on other contributers commits. I unexpectedly closed the PR while fixing it. I will resubmit the changes soon

[iche033]

you changes look good,

Like you mentioned, you signed off commits from other authors. I still see this. Are you able to fix them? You can do a rebase and take only your commits and rebase them on the gz-rendering9 branch

[dheerubhai-101]

hi Ian, rebased it as you said. It only includes my commits now. Thanks for the help man

[iche033]

great, thanks for the contribution!

comments addressed