How do I visualize coordinate frames in Drake using Meshcat?

Question

How can I view coordinate frames from Drake in Meschcat? I only found this related question about Drake Visualizer but had trouble finding the equivalent code for Meshcat.

I have made some progress and got a coordinate frame at the origin using

    AddFrameTriadIllustration(scene_graph=scene_graph, plant=plant, frame_id=plant.world_frame_id())

However, I want a coordinate frame displayed at my robot's end effector. I'm having trouble determining how to obtain a frame id that's not the world_frame_id.

Answer 1

To visualize a frame that's offset from a SceneGraph frame, call pydrake.visualization.AddFrameTriadIllustration. If the base frame is the world frame, then the X_FT you provide would be the world pose of what you're trying to visualize.

Here's a link to a sample usage to visualize all of the existing frames.

In case the link disappears, the snippet is reproduced below.

# https://github.com/RobotLocomotion/drake/blob/v1.19.0/bindings/pydrake/visualization/_model_visualizer.py#L257-L274
if self._visualize_frames:
    # Find all the frames and draw them.
    # The frames are drawn using the parsed length.
    # The world frame is drawn thicker than the rest.
    inspector = self._builder.scene_graph().model_inspector()
    for frame_id in inspector.GetAllFrameIds():
        world_id = self._builder.scene_graph().world_frame_id()
        radius = self._triad_radius * (
            3 if frame_id == world_id else 1
            )
        AddFrameTriadIllustration(
            plant=self._builder.plant(),
            scene_graph=self._builder.scene_graph(),
            frame_id=frame_id,
            length=self._triad_length,
            radius=radius,
            opacity=self._triad_opacity,
        )