When I reproduced gcs-science-robotics in the latest version of drake and ran prm_comparison.ipynb, I met this problem.

RuntimeError                              Traceback (most recent call last)
/tmp/ipykernel_16980/4066659220.py in <module>
----> 1 visualize_trajectory(meshcat, [linear_gcs_traj],
      2                      show_path=True,
      3                      robot_configurations=execute_task,
      4                      transparency=0.3)

~/lhc-gcs-science-robotics/reproduction/prm_comparison/helpers.py in visualize_trajectory(meshcat, trajectories, show_path, robot_configurations, transparency, regions)
    246 
    247     # Set transparency of main arm and gripper.
--> 248     set_transparency_of_models(plant,
    249                                [iiwa.model_instance, wsg.model_instance],
    250                                transparency, scene_graph)

~/lhc-gcs-science-robotics/reproduction/prm_comparison/helpers.py in set_transparency_of_models(plant, model_instances, alpha, scene_graph)
    122                                                        Role.kIllustration):
    123                 properties = inspector.GetIllustrationProperties(geometry_id)
--> 124                 phong = properties.GetProperty("phong", "diffuse")
    125                 phong.set(phong.r(), phong.g(), phong.b(), alpha)
    126                 properties.UpdateProperty("phong", "diffuse", phong)

RuntimeError: GetProperty(): Trying to read property ('phong', 'diffuse'), but the group does not exist.

then I found that properties group name was '__default__'. I want to know that if API changed what should I do to change the transparency of models.

When I reproduced gcs-science-robotics in the latest version of drake and ran prm_comparison.ipynb, I met this problem.

RuntimeError                              Traceback (most recent call last)
/tmp/ipykernel_16980/4066659220.py in <module>
----> 1 visualize_trajectory(meshcat, [linear_gcs_traj],
      2                      show_path=True,
      3                      robot_configurations=execute_task,
      4                      transparency=0.3)

~/lhc-gcs-science-robotics/reproduction/prm_comparison/helpers.py in visualize_trajectory(meshcat, trajectories, show_path, robot_configurations, transparency, regions)
    246 
    247     # Set transparency of main arm and gripper.
--> 248     set_transparency_of_models(plant,
    249                                [iiwa.model_instance, wsg.model_instance],
    250                                transparency, scene_graph)

~/lhc-gcs-science-robotics/reproduction/prm_comparison/helpers.py in set_transparency_of_models(plant, model_instances, alpha, scene_graph)
    122                                                        Role.kIllustration):
    123                 properties = inspector.GetIllustrationProperties(geometry_id)
--> 124                 phong = properties.GetProperty("phong", "diffuse")
    125                 phong.set(phong.r(), phong.g(), phong.b(), alpha)
    126                 properties.UpdateProperty("phong", "diffuse", phong)

RuntimeError: GetProperty(): Trying to read property ('phong', 'diffuse'), but the group does not exist.

then I found that properties group name was '__default__'. I want to know that if API changed what should I do to change the transparency of models.

• python
• drake

1 Answer 1

I believe the error comes from the fact that your plant has geometries with an Illustration role, but they don't already have the ("phong", "diffuse") property assigned.

Specifically, set_transparency_of_models() is assuming that the property has already been assigned (so it simply calls GetProperty()). When the property doesn't already exist, it blows up as you've observed.

So, there are two ways to resolve this:

1. Make sure that every geometry in your plant with the IllustrationRole has the expected property assigned, and/or

2. Modify the code in question so that instead of calling GetProperty() it calls GetPropertyOrDefault() and have the function provide a default Rgba to use in the absence of a pre-assigned diffuse color.