Recording multiple meshcat visualizers

Question

I would like to record multiple meshcat visualizers with different prefix ids so I can eventually save them to an HTML file that I can interact with later. I would like the different visualizations to play on top of each other and to be able to select/unselect different visualizations.

Here is a minimal replication of the problem. I expect there to be two cartpole visualizations that are on top of each other. However, I only end up seeing one of them being recorded. The other cartpole seems stuck at the end position when I play back the recording

import meshcat
from pydrake.common import FindResourceOrThrow

from pydrake.multibody.plant import (
    AddMultibodyPlantSceneGraph)
from pydrake.multibody.parsing import Parser
from pydrake.systems.analysis import Simulator
from pydrake.systems.framework import DiagramBuilder
from pydrake.systems.meshcat_visualizer import (
    ConnectMeshcatVisualizer,
)

v = meshcat.Visualizer()
file_name = FindResourceOrThrow(
    "drake/examples/multibody/cart_pole/cart_pole.sdf")
builder = DiagramBuilder()
cart_pole, scene_graph = AddMultibodyPlantSceneGraph(builder, 0.0)
Parser(plant=cart_pole).AddModelFromFile(file_name)
cart_pole.Finalize()

vis = ConnectMeshcatVisualizer(builder=builder,
                                prefix="vis",
                                scene_graph=scene_graph,
                                open_browser=False)

vis2 = ConnectMeshcatVisualizer(
    builder=builder,
    prefix="vis2",
    scene_graph=scene_graph,
    open_browser=False)
vis2.set_name("vis2")

diagram = builder.Build()
diagram_context = diagram.CreateDefaultContext()

cart_pole_context = diagram.GetMutableSubsystemContext(
    cart_pole, diagram_context)
cart_pole.get_actuation_input_port().FixValue(cart_pole_context, .02)

simulator = Simulator(diagram, diagram_context)
simulator.set_publish_every_time_step(False)
vis.start_recording()
vis2.start_recording()
simulator.AdvanceTo(100)
vis.stop_recording()
vis2.stop_recording()

vis.publish_recording()
vis2.publish_recording()

# f = open("saved.html", "w")
# f.write(v.static_html())
# f.close()

score 2 · Accepted Answer · answered Nov 11 '20 at 02:41

Here is one solution. I don't love it, but it accomplishes the stated goal. Note the changes:

saving and publishing only one animation
naming the model in the MultibodyPlant with a distinct name for each sim
setting delete_prefix_on_load=False so it doesn't clear the old geometry

import meshcat
from pydrake.common import FindResourceOrThrow

from pydrake.multibody.plant import (AddMultibodyPlantSceneGraph)
from pydrake.multibody.parsing import Parser
from pydrake.systems.analysis import Simulator
from pydrake.systems.framework import DiagramBuilder
from pydrake.systems.meshcat_visualizer import (
    ConnectMeshcatVisualizer,
)

animation = None

for i in range(3):
    file_name = FindResourceOrThrow(
        "drake/examples/multibody/cart_pole/cart_pole.sdf")
    builder = DiagramBuilder()
    cart_pole, scene_graph = AddMultibodyPlantSceneGraph(builder, 0.0)
    Parser(plant=cart_pole).AddModelFromFile(file_name, f"plant{i}")
    cart_pole.Finalize()

    vis = ConnectMeshcatVisualizer(builder=builder,
                                   scene_graph=scene_graph,
                                   delete_prefix_on_load=False,
                                   open_browser=False)
    if animation:
        vis._animation = animation

    diagram = builder.Build()
    diagram_context = diagram.CreateDefaultContext()

    cart_pole_context = diagram.GetMutableSubsystemContext(
        cart_pole, diagram_context)
    cart_pole.get_actuation_input_port().FixValue(cart_pole_context, .02)

    simulator = Simulator(diagram, diagram_context)
    simulator.set_publish_every_time_step(False)
    vis.start_recording()
    simulator.AdvanceTo(10)
    vis.stop_recording()
    animation = vis._animation

vis.publish_recording()

Recording multiple meshcat visualizers

1 Answers1