PhysX Shape operator

The PhysX Shape operator allows you to convert particles into PhysX rigidbodies.

Hull Rollout

Hull Type

  • Hull Type: allows you to choose the particle rigidbody collision hull.

Sphere: a perfectly spherical hull.

Box: a bounding box hull.

Convex Hull: a convex hull encapsulating particle shape mesh vertices.

Mesh: the particle’s shape mesh will be used as the hull.

Dynamic mesh hulls are not supported. Particle rigidbodies with a mesh hull will be set to kinematic.

  • Display Hull: displays the rigidbody hull in the viewport.

Convex Hull

  • Max verts: the max number of verts allows in the convex hull.

Shape Optimization

  • Sphere Override: Forces spherical hulls for particles with a radius below a certain threshold.

  • Max Radius: the radius threshold.

  • Box Override: Forces bounding box hulls for particles with a radius below a certain threshold.

  • Max Radius: the radius threshold.

Shape Dimensions

  • Fit Bounding Box: controls whether spherical hulls will encapsulate the bounding box of the particle’s shape mesh.

  • Size Mult: the size multiplier for the hull.

  • Min radius: the minimum radius constraint on spherical hulls.

  • Min Length/Width/Height: minimum dimension constraints on box hulls.

Dynamics Rollout

Bounce and Friction

  • Restitution: the restitution coefficient for the rigidbody. Similar to “bounce”.

  • Static/Dynamic friction: friction coefficients for the rigidbody.


  • Override: controls whether particle masses will be overridden by this operator.

  • Value: the desired mass value.

  • Relative to volume: controls whether assigned mass values will be relative to particle shape volume.

  • Target volume: the target volume that particle volumes will be compared to, when assigning mass values.

  • Exponent: the exponent that particle volume ratios will be raised to. Larger exponent values will increase the mass disparity between large and small volumes.

  • Min Value: the minimum allowed mass value.

  • Max Value: the maximum allowed mass value.


  • Angular Damping: the amount of damping to apply to angular (spin) forces acting on rigidbodies.

  • Linear Damping: the amount of damping to apply to linear (movement) forces acting on rigidbodies.

“Damping” is an effect which reduces the strength of forces over time. Increasing these values will cause particles to spin/move slower over time.

Velocity Limits

  • Impulse: the maximum impulse (collision) velocity limit for rigidbodies.

  • Angular: the maximum angular (spin) velocity limit for rigidbodies.

  • Exit: the maximum exit (penetration correction) velocity limit for rigidbodies.

Decreasing these values can help prevent jittering and explosive forces that develop as the result of interpenetrations between rigidbodies.


  • Position X/Y/Z: per-axis position locks on rigidbodies.

  • Rotation X/Y/Z: per-axis rotation locks on rigidbodies.

Collisions Rollout

Collision Tolerance

  • Penetration offset: the maximum distance that rigidbodies are allowed to penetrate each other.

  • Contact sensitivity: the maximum inflation distance for rigidbody contact detection.

Simulation Groups

  • Only Collide With: controls whether rigidbodies will only be able to collide with certain simulation groups.

  • Simulation groups: controls which particle simulation groups will be used to filter collisions.

Start Penetrations

  • Ignore start penetrations: controls whether initial penetrations between rigidbodies will be ignored.

  • Simulation groups: controls which particle simulation groups will be used to filter starting penetrations.

If the initial state of your simulation features overlapping rigidbodies, “ignore start penetrations” can prevent explosive forces from being added to the system in order to resolve those penetrations.

Penetration resolution between initially-interpenetrating rigidbodies will resume once the rigidbodies fully separate.