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[isaacsim.robot_setup.virtual_gantry] Virtual Gantry#

Version: 0.3.0

Virtual Gantry#

The Virtual Gantry suspends a robot from an anchor point during bring-up and policy testing — like a crane holding the robot so it does not fall over while you iterate on locomotion or system identification.

It is a runtime constraint only: a one-sided spring-damper “rope” applied as a per-physics-step external wrench to a single articulation body. There is no USD joint and no kinematic anchor; all six base DOFs stay free. The rope applies no force until the body drops past the rope length, then it pulls the body back toward the anchor.

Usage#

  1. Create > Robotics > Virtual Gantry authors an IsaacVirtualGantry prim (an Xform whose world position is the anchor), placed above the selected prim by default. You can also script it with isaacsim.robot_setup.virtual_gantry.create_virtual_gantry(stage, path).

  2. Set the prim’s Attach Body relationship to the link the rope pulls on (e.g. the torso) and the Articulation relationship to the robot’s articulation root. Move the prim to place the anchor.

  3. Tune Rope Length, Stiffness, Damping in the property panel; a rope length of -1 auto-derives from the body’s height on the first step.

  4. Press Play. Toggle the rope with Enable / Disable in the property panel or the G hotkey; shorten / lengthen it with [ / ] (the viewport must have keyboard focus). Disable it once a policy is balancing.

Notes#

  • Backend: PhysX and Newton. The rope reads the attach link’s pose and applies its wrench through the articulation tensor view (get_link_transforms / apply_forces_and_torques_at_position); that view is engine-agnostic, so no backend-specific code is needed. Verified in a local build on both isaac-sim.sh and isaac-sim.newton.sh.

  • The anchor uses the prim’s position only; orientation is reserved for a future 6-DOF “soft fixture” mode.

  • The force law matches the established MuJoCo virtual-gantry behavior, so a policy behaves the same whether suspended in MuJoCo or Isaac Sim.

Preview

Enable Extension#

The extension can be enabled (if not already) in one of the following ways:

Define the next entry as an application argument from a terminal.

APP_SCRIPT.(sh|bat) --enable isaacsim.robot_setup.virtual_gantry

Define the next entry under [dependencies] in an experience (.kit) file or an extension configuration (extension.toml) file.

[dependencies]
"isaacsim.robot_setup.virtual_gantry" = {}

Open the Window > Extensions menu in a running application instance and search for isaacsim.robot_setup.virtual_gantry. Then, toggle the enable control button if it is not already active.