Meshcat轨迹可视化报错：C++对象所有权问题及替代方案咨询

你遇到的RuntimeError是因为最初创建的scene_graph已经被第一个DiagramBuilder构建的diagram接管了所有权，PyBind11不再拥有它的控制权，所以没法再把它加到新的DiagramBuilder里。

方法1：直接回放轨迹到原Diagram #

不用重新搭建系统，直接用原有的diagram和scene_graph，遍历轨迹的每个状态并渲染：

trajectory = dircol.ReconstructStateTrajectory(result)
times = trajectory.get_segment_times()
states = trajectory.vector_values(times)

# 初始化原场景的可视化器
visualizer = PlanarSceneGraphVisualizer(
    scene_graph, xlim=[-4, 4], ylim=[-2, 2], show=True
)
context = diagram.CreateDefaultContext()

# 逐个时间点更新状态并绘制
for t, x in zip(times, states.T):
    diagram.get_mutable_context(context).SetTime(t)
    plant.get_mutable_state_input_port().FixValue(context, x)
    visualizer.draw(context)

方法2：重新构建Plant和SceneGraph #

既然原scene_graph不能复用，就重新建一套相同的Plant和SceneGraph来加载模型，再连接轨迹源：

trajectory = dircol.ReconstructStateTrajectory(result)

# 重新构建Multibody Plant和SceneGraph
builder = DiagramBuilder()
plant_new, scene_graph_new = AddMultibodyPlantSceneGraph(builder=builder, time_step=0)
parser = Parser(plant_new)
ConfigureParser(parser)
parser.AddModelsFromString(minigolf_urdf, 'urdf')
plant_new.Finalize()

# 轨迹源连接到姿态转换模块
source = builder.AddSystem(TrajectorySource(trajectory))
pos_to_pose = builder.AddSystem(
    MultibodyPositionToGeometryPose(plant_new, input_multibody_state=True)
)
builder.Connect(source.get_output_port(0), pos_to_pose.get_input_port())
builder.Connect(
    pos_to_pose.get_output_port(),
    scene_graph_new.get_source_pose_port(plant_new.get_source_id()),
)

# 添加可视化器并运行
visualizer = builder.AddSystem(
    PlanarSceneGraphVisualizer(
        scene_graph_new, xlim=[-4, 4], ylim=[-2, 2], show=True
    )
)
builder.Connect(scene_graph_new.get_query_output_port(), visualizer.get_input_port(0))

diagram_new = builder.Build()
context_new = diagram_new.CreateDefaultContext()
diagram_new.ForcedPublish(context_new)
visualizer.run()

内容的提问来源于stack exchange，提问作者Ben Kang