[Feature request]: Support top-view thumbnail generator in Gz Harmonic

[aaronchongth]

Before proceeding, is there an existing issue or discussion for this?

• I have done a search for similar issues and discussions.

Description

The thumbnail generator is helpful for creating thumbnails at a fixed scale, to populate top-down editors like traffic-editor with models.

The goal would be to

• migrate the legacy thumbnail generator implementation (supports Gazebo classic only) and support Gazebo Harmonic onwards
• update documentation on how to generate thumbnails

A good reference would also be the upstream gazebo model prop shop system plugin, that is used for generating thumbnails before uploading models onto Fuel.

Relevant links and references:

• legacy implementation for gazebo classic: https://github.com/open-rmf/rmf_simulation/blob/humble/rmf_building_sim_gz_classic_plugins/src/thumbnail_generator.cpp
• generated thumbnails: https://github.com/open-rmf/rmf_traffic_editor/tree/main/rmf_traffic_editor_assets
• legacy instructions: https://github.com/open-rmf/rmf_traffic_editor/tree/main/rmf_traffic_editor#generating-custom-thumbnails
• gz model prop shop plugin as a reference: https://github.com/gazebosim/gz-sim/blob/gz-sim9/src/systems/model_photo_shoot/ModelPhotoShoot.cc
• gz model prop shop world as a reference: https://github.com/gazebosim/gz-sim/blob/gz-sim9/examples/worlds/model_photo_shoot.sdf

Implementation Considerations

No response

Alternatives

No response

Additional information

No response

[luca-della-vedova]

From what I understand, the only reason the ModelPhotoShoot plugin doesn't work for our use case is that it tries to generate constant sized thumbnails by positioning the camera further / closer depending on how large the object is, while in our case we want to know how big they are so we don't want that behavior.
After discussing at the PMC meeting, I feel that the best way forward for this would be to update the ModelPhotoShoot gz system to allow for fixed camera distance model shooting so we can have the scale information in the thumbnail.