Support locked entities, and headless video recording using sim time

[nkoenig]

Signed-off-by: Nate Koenig [email protected]

🎉 New feature

Related PR: gazebosim/gz-sensors#137

Summary

The goal of this PR is to support generating videos from log files using a headless simulation instance. In order to accomplish this, I need to spawn a camera into simulation and keep that camera around during log seeks. This lead to the need for locked entities within the ECM.

Recording a video using simulation time is required when you want a video to playback at real-time speeds. I copied the sim time video recording code from the Scene3d plugin.

Test it

There are ECM tests for the locking feature.
The easiest way to test the sim time video recording is to use the camera_video_record_dbl_pendulum.sdf example world file, and add <use_sim_time>true</use_sim_time> to the plugin. Depending on your machine, you may have to adjust the physics step to make sure simulation is running slower than real-time. Record a video, and note the simulation time duration for the video. The resulting video should have matching duration, which can be inspected using:

mplayer -identify VIDEO.MP4 2>/dev/null | grep ID_LENGTH

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• 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

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[codecov]

Codecov Report

Merging #862 (1818019) into ign-gazebo4 (8ab51a3) will increase coverage by 0.01%.
The diff coverage is 92.68%.

❗ Current head 1818019 differs from pull request most recent head f70a4e1. Consider uploading reports for the commit f70a4e1 to get more accurate results

@@               Coverage Diff               @@
##           ign-gazebo4     #862      +/-   ##
===============================================
+ Coverage        67.10%   67.12%   +0.01%     
===============================================
  Files              243      243              
  Lines            18212    18250      +38     
===============================================
+ Hits             12222    12251      +29     
- Misses            5990     5999       +9     

Impacted Files	Coverage Δ
include/ignition/gazebo/EntityComponentManager.hh	100.00% <ø> (ø)
src/gui/plugins/scene3d/Scene3D.cc	9.91% <ø> (ø)
src/EntityComponentManager.cc	87.24% <92.68%> (+0.30%)	⬆️
src/gui/plugins/entity_tree/EntityTree.cc	9.62% <0.00%> (-3.21%)	⬇️

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[iche033]

The sim time video recording feature is working for me. I also tried running faster than real time and that's working as well and produced the correct video length. (RTF just drops a little when video recording is on).

another nice video recorder param that we could port over later from Scene3D is so users can record high quality videos.

[iche033]

another nice video recorder param that we could port over later from Scene3D is so users can record high quality videos.

#864

[mjcarroll]

LGTM with Green CI (minus tests we know are flaky)