PhysX Bind operator

The PhysX Bind operator can be used to create bindings between PhysX particles.

PhysX bindings are not solved by this operator, only created. PhysX bindings are solved by the global PhysX solver at the end of each simulation step. PhysX bindings created by this operator will persist between events.


PhysX Bind Rollout

Type

  • Binding type: the type of binding to apply to applicable particles

Distance (Tether): A stiff distance-based binding, that will try to maintain a certain distance between bind points on two PhysX particle rigidbodies.

Distance (Spring): A stretchy distance-based binding, that will try to maintain a certain distance between bind points on two PhysX particle rigidbodies, based on spring/damping settings.

Rigid (Glue): a stiff transform-based binding, that will try to maintain perfectly rigid cohesion between PhysX particle rigidbodies.

Rigid (Joint): a soft transform-based binding, that will try to maintain some level of cohesion between PhysX particle rigidbodies, based on spring/damping settings.

Sometimes it is better to use Rigid (Joint) bindings with very high spring stiffness, instead of Rigid (Glue) bindings, in order to simulate PhysX particles that are meant to be stuck together. If your Rigid (Glue) bindings enter into a degenerate state that cannot be properly solved, they may introduce more artifacts into a simulation than Rigid (Joint) bindings with very high stiffness.

Bind Settings

  • Binding ID: the ID of created bindings.

  • Enable collisions: controls whether bound PhysX particle rigidbodies should also collide with each other.

  • Scale with particles: controls whether bindings will be automatically adjusted to match the scale of the particles they are attached to, if their scale changes.

Movement settings
  • Enable spring: enables positional springs.

  • Spring stiffness: the stiffness of the springs.

  • Damping: the damping applied to the springs.

  • Restitution: the restitution applied to the springs.

  • Limit: the positional limit of the binding. The solver will attempt to ensure positional deltas do not exceed this value.

  • Length enable: enables a length-override on the binding.

  • Length: the length-override value.

  • Stretch %: the maximum allowed stretch ratio of the binding.

  • Compress %: the maximum allowed compression ratio of the binding.

Swing settings
  • Enable spring: enables swing springs.

  • Spring stiffness: the stiffness of the springs.

  • Damping: the damping applied to the springs.

  • Restitution: the restitution applied to the springs.

  • Limit Y: the rotational limit of the binding, around the Y axis.

  • Limit Z: the rotational limit of the binding, around the Z axis.

Twist settings
  • Enable spring: enables twist springs.

  • Spring stiffness: the stiffness of the springs.

  • Damping: the damping applied to the springs.

  • Restitution: the restitution applied to the springs.

  • Limit Min: the rotational minimum limit of the binding, around the X axis.

  • Limit Max: the rotational maximum limit of the binding, around the X axis.

Strength volume multiplier

The volume multiplier will adjust spring/damping values based on the ratio between the volume of particle shape meshes and a target value.

  • Affect spring: controls whether the volume multiplier will apply to spring values.

  • Affect damping: controls whether the volume multiplier will apply to damping values.

  • Target volume: the target volume to which the volume of particle shape meshes will be compared.

  • Min multiplier: the minimum value of the resulting multiplier.

  • Max multiplier: the maximum value of the resulting multiplier.

  • Exponent: the exponent to which the ratio between the particle shape mesh volume and the target value will be raised.

Display

  • Show bindings: bindings between PhysX particle rigidbodies will be drawn in the viewport.

  • Show connections: a connection will be drawn between bound PhysX particles.

  • Show endpoints: a dot marker will be drawn on either end of the displayed bindings/connections.

If two bound particles are close enough together, their PhysX binding length will be very small - or even zero - so “show bindings” will not be very useful. By choosing “show connections” instead, lines will be drawn between the particles themselves, not simply the locations of their binding’s endpoints, so it may be easier to visualize their relationship. Alternatively, you can enable “show endpoints” to display dot markers on either end of display lines, which will help line visibility when line length is close to zero.


Bind Breaking Rollout

Breaking

  • Enable force breaking: enables bind breaking based on a force threshold.

  • Force: a force differential greater than this value between two bound particles will cause their binding to break.

  • Enable torque breaking: enables bind breaking based on a torque threshold.

  • Torque: a torque differential greater than this value between two bound particles will cause their binding to break.

  • Enable stretch breaking: enables bind breaking based on a stretch threshold.

  • Stretch %: bindings that stretch beyond this ratio will break.

  • Enable compression breaking: enables bind breaking based on a compression threshold.

  • Compress %: bindings that compress beyond this ratio will break.

  • Enable bend breaking: enables bind breaking based on a bend threshold.

  • Bend angle: bindings that bend beyond this angle will break.

Variation %: the per-particle percentage of variation to apply.

Deforming

  • Enable bend deforming: bindings that bend beyond a certain angle will reset their rest transformation offset.

  • Bend angle: the bend angle threshold.

Variation %: the per-particle percentage of variation to apply.

Proximity Bind Rollout

  • Particles/Colliders/Ground/World: controls which rigidbodies of a simulation each particle can be bound to, by proximity.

Sample

  • Sample type: controls which sampler will be used to determine closest-surface proximities for particles.

  • Bind distance: the maximum distance between a particle and an enabled binding rigidbody required in order for a new binding to be created between them.

  • Max binds: the maximum number of bindings a particle may form between itself and other relevant rigidbodies.

Variation %: the per-particle percentage of variation to apply.
  • Improve anchor accuracy: extra effort will be made to ensure the binding anchor points will be as close together as possible, on the surface of the corresponding rigidbodies.

Rigidbody sorting

When the total number of valid neighbor rigidbodies exceeds the “max binds” value, these settings control how to sort the results.

  • Unsorted: no sorting will occur.

  • Sort by distance (closest): the rigidbodies will be sorted from closest to furthest.

  • Sort by distance (furthest): the rigidbodies will be sorted from furthest to closest.

  • Sort by volume (biggest): the rigidbodies will be sorted from biggest to smallest by volume.

  • Sort by volume (smallest): the rigidbodies will be sorted from smallest to biggest by volume.

  • Sort by surface area (biggest): the rigidbodies will be sorted from biggest to smallest by surface area.

  • Sort by surface area (smallest): the rigidbodies will be sorted from smallest to biggest by surface area.


Simulation Groups

  • Simulation groups: controls which rigidbody simulation groups will be bind candidates.

Clusters

  • Enable clustering: controls whether binding candidates will be determined by cluster values.

  • Channel: the particle data channel to get cluster values from.

  • Cluster if equal: binding candidates must have equal cluster values.

  • Cluster if equal: binding candidates must have unequal cluster values.

Family filtering

  • Bind All: all rigidbodies will be bound, ignoring their relationships.

  • Bind siblings: only sibling particles will be bound to each other.

  • Bind non-siblings: only non-siblings will be bound to each other.


Point Bind Rollout

Point Bind

Point bindings are bindings whose location is controlled by the positions of objects in space.

Proximity bindings will form at the nearest points between two rigidbodies. However, sometimes it is necessary to exert more precise control over the locations of the binding anchor points. Point bindings allow you to control where binding anchor points are set, by positioning a target object in space and ensuring its sweep sphere overlaps the target rigidbodies. Resulting bindings will place their anchor points as close to the target object as possible.

  • Particles/Colliders/Ground/World: controls which rigidbodies of a simulation each particle can be bound to, by points.

  • Sweep size: the sweep size of each target object’s sweep sphere.

Point bindings will only be created between rigidbodies that overlap the target object’s sweep spheres.

Objects

  • Input object list: the list of target objects.

Display

  • Show sweep spheres: draws the target object sweep spheres in the viewport.

Family Bind Rollout

  • Bind to siblings: controls whether sibling particles will be bound to each other.

  • Bind to parent: controls whether child particles will be bound to their parent particle.


Actor Bind Rollout

  • Enable actor bindings: enables bindings between actor rig particles, whose bind setup ID matches a specified value.

  • Bind setup ID: the bind setup ID to match.