Implementation:Isaac sim IsaacGymEnvs SkeletonPlotterTasks

Knowledge Sources	IsaacGymEnvs
Domains	Visualization, Skeleton_Animation
Last Updated	2026-02-15 11:00 GMT

Overview

SkeletonPlotterTasks defines composite visualization tasks for rendering 3D skeleton states, skeleton motions with velocity indicators and trails, and collections of multiple skeleton motions.

Description

The Draw3DSkeletonState class renders a single skeleton pose by decomposing it into two primitive sub-tasks: Draw3DLines for the bones (connecting parent-child joint pairs) and Draw3DDots for the joint positions. It extracts global translations from a SkeletonState object and traverses the skeleton tree's parent indices to construct line segments between each joint and its parent. The update() method accepts a new skeleton state and refreshes both the line and dot data.

The Draw3DSkeletonMotion class builds upon Draw3DSkeletonState to visualize animated skeleton motion. In addition to the skeleton pose, it renders velocity vectors and angular velocity vectors as Draw3DLines (scaled by 0.02 and 0.01 respectively for visual clarity), and a center-of-mass trail using Draw3DTrail. The trail maintains a rolling buffer of recent root positions with a configurable trail_length. The update() method supports advancing to a specific frame index, optionally resetting the trail, and replacing the entire skeleton motion data.

The Draw3DSkeletonMotions class is a container that wraps multiple Draw3DSkeletonMotion instances and synchronizes their updates to the same frame index, enabling side-by-side comparison of multiple motion sequences.

Usage

Use Draw3DSkeletonState when you need to visualize a single static skeleton pose. Use Draw3DSkeletonMotion for interactive playback of motion clips with velocity and trail indicators. Use Draw3DSkeletonMotions when comparing multiple motion sequences simultaneously. These tasks are the primary visualization tools used during motion retargeting, AMP reference motion inspection, and debugging of skeleton-based reinforcement learning environments.

Code Reference

Source Location

• Repository: IsaacGymEnvs
• File: isaacgymenvs/tasks/amp/poselib/poselib/visualization/skeleton_plotter_tasks.py
• Lines: 40-217

Signature

class Draw3DSkeletonState(BasePlotterTask):
    def __init__(self, task_name: str, skeleton_state,
                 joints_color: str = "red", lines_color: str = "blue",
                 alpha: float = 1.0) -> None: ...
    def update(self, skeleton_state) -> None: ...
    @staticmethod
    def _get_lines_and_dots(skeleton_state): ...

class Draw3DSkeletonMotion(BasePlotterTask):
    def __init__(self, task_name: str, skeleton_motion,
                 frame_index=None, joints_color="red", lines_color="blue",
                 velocity_color="green", angular_velocity_color="purple",
                 trail_color="black", trail_length=10, alpha=1.0) -> None: ...
    def update(self, frame_index=None, reset_trail=False,
               skeleton_motion=None) -> None: ...
    @staticmethod
    def _get_vel_and_avel(skeleton_motion): ...

class Draw3DSkeletonMotions(BasePlotterTask):
    def __init__(self, skeleton_motion_tasks) -> None: ...
    def update(self, frame_index) -> None: ...

Import

from isaacgymenvs.tasks.amp.poselib.poselib.visualization.skeleton_plotter_tasks import Draw3DSkeletonState, Draw3DSkeletonMotion

I/O Contract

Inputs

Name	Type	Required	Description
task_name	str	Yes	Unique identifier for the skeleton drawing task
skeleton_state	SkeletonState	Yes (for Draw3DSkeletonState)	A poselib SkeletonState with global translations and skeleton tree
skeleton_motion	SkeletonMotion	Yes (for Draw3DSkeletonMotion)	A poselib SkeletonMotion containing frames of skeleton states with velocities
frame_index	int	No	Specific frame to display from the motion (default: None uses full tensor)
joints_color	str	No	Color for joint dots (default: "red")
lines_color	str	No	Color for bone lines (default: "blue")
velocity_color	str	No	Color for velocity vectors (default: "green")
angular_velocity_color	str	No	Color for angular velocity vectors (default: "purple")
trail_color	str	No	Color for center-of-mass trail (default: "black")
trail_length	int	No	Number of historical positions in the trail buffer (default: 10)
alpha	float	No	Transparency value from 0.0 to 1.0 (default: 1.0)
reset_trail	bool	No	Whether to reset the trail on update (default: False)

Outputs

Name	Type	Description
lines_task	Draw3DLines	Sub-task rendering bone line segments between parent-child joints
dots_task	Draw3DDots	Sub-task rendering joint position markers
vel_task	Draw3DLines	Sub-task rendering velocity vectors at each joint (Draw3DSkeletonMotion only)
avel_task	Draw3DLines	Sub-task rendering angular velocity vectors at each joint (Draw3DSkeletonMotion only)
com_trail_task	Draw3DTrail	Sub-task rendering center-of-mass motion trail (Draw3DSkeletonMotion only)

Usage Examples

from isaacgymenvs.tasks.amp.poselib.poselib.visualization.skeleton_plotter_tasks import (
    Draw3DSkeletonState, Draw3DSkeletonMotion, Draw3DSkeletonMotions
)
from poselib.skeleton.skeleton3d import SkeletonState, SkeletonMotion

# Visualize a single skeleton state (T-pose)
tpose = SkeletonState.from_file("data/amp_humanoid_tpose.npy")
state_task = Draw3DSkeletonState(
    "humanoid_tpose", tpose,
    joints_color="red", lines_color="blue"
)

# Visualize animated skeleton motion with velocity indicators
motion = SkeletonMotion.from_file("data/amp_humanoid_walk.npy")
motion_task = Draw3DSkeletonMotion(
    "humanoid_walk", motion,
    frame_index=0,
    trail_length=20,
    velocity_color="green"
)

# Advance to next frame
motion_task.update(frame_index=1)

# Reset trail when restarting playback
motion_task.update(frame_index=0, reset_trail=True)

# Iterate over primitive sub-tasks for rendering
for primitive in motion_task:
    print(primitive.task_name, primitive.task_type)