Force#

If a mutable has attribute type of force, it’s a force mutable that applies PhysX forces to rigid bodies. Forces can be used to create dynamic simulations with objects being pushed, pulled, or animated through physics.

Available attributes of force:

Name	Type	Description
target	string	The name of the target mutable (must be a rigidbody). Do not use `$[...]` syntax - just use the mutable name directly (e.g., `target: rocket`). The target must be defined before the force in the YAML.
force	list	Force vector as [x, y, z]. Can be a constant value or animated using keyframes.
torque	list	Torque vector as [x, y, z]. Optional. Can be a constant value or animated using keyframes.
enabled	bool	Whether the force is enabled. Defaults to `True`. Can be animated using keyframes.
animation	dict	Keyframe animation for force, torque, enabled, and transform operators. See below for details.
transform_operators	list	Transform operators for local offset of the force application point. Can be animated.

Constant Force

A constant force applies the same force vector throughout the simulation:

rocket_thrust:
  type: force
  target: rocket
  force: [0, 0, 2000]  # Upward force
  enabled: true

Animated Force

An animated force uses keyframes to change force properties over time. The animation dictionary contains keyframe sequences for force, torque, enabled, and transform operators like translate.

Example of animated force:

rocket_thrust:
  type: force
  target: rocket
  animation:
    force:
      keyframes:
      - time: 0
        value:
        - distribution_type: range
          start: -50
          end: 50
        - 0
        - distribution_type: range
          start: 1500
          end: 1900
      - time: 20
        value:
        - distribution_type: range
          start: -50
          end: 50
        - 0
        - 1300
    enabled:
      keyframes:
      - time: 0
        value: true
      - time: 50
        value: false
    translate:
      keyframes:
      - time: 0
        value: [0, 0, 0]
      - time: 20
        value: [0, 2, 0]  # Vibrate effect
      - time: 25
        value: [0, 0, 0]

Notes

The target must be a rigidbody geometry. The force is applied as a child prim of the target.
For animated forces, the X component of the force vector is randomized once and shared across all keyframes (matching ForceDemo.py behavior).
Transform operators in animation (like translate) can be used to create vibration or movement effects at the force application point.
Forces are applied in local space relative to the target prim.