The Collision operator can be used to collide particles with scene geometry.
The Collider operator supports static/deforming geometry objects, as well as built-in Deflector/SDeflector spacewarps.
Enable ground collider: when enabled, a virtual ground collider will be created, allowing particles to bounce off the ground without the need for an actual ground collider object in the scene.
Z-offset: the distance along the Z-axis of the scene to offset the ground collider.
Absolute radius: the collision radius of each particle will be set to a specific value.
Radius: the specific collision radius value.
Shape radius: the collision radius of each particle will be set to each particle’s shape mesh radius.
Scale radius: the collision radius of each particle will be set to each particle’s maximum scale dimension.
Multiplier: the multiplier to apply to shape/scale radius values.
Collides: the test condition will be satisfied as soon as a particle collides with a collider object.
Collides multiple times: the test condition will be satisfied as soon as a particle collides with a collider a specified number of times.
Count: the number of times a particle must hit a collider in order to satisfy the test condition.
Bounce: Particles will bounce off colliders.
Continue: Particle will not be affected by colliders (but may still satisfy the test condition).
Collide with front faces: particles will only collide with the fronts of faces.
Collide with back faces: particles will only collide with the backs of faces.
Collide with both: particles will collide with fronts and backs of faces.
Pass-Through %: controls the number of particles that are allowed to pass through the collider.
Bounce %: the bounce velocity of particles, relative to their travel velocity.
Diverge %: the percentage of divergence to apply to bounce vectors.
Threshold: particles whose travel velocity magnitude is below this value will not bounce.
Friction %: the friction applied to particles, relative to their travel velocity.
Threshold: particles whose travel velocity magnitude is below this value will be treated with 100% friction.
Inherit %: the percentage of collider surface velocity that particles will inherit.
Values above 0 help prevent floating-point precision errors during collision detection calculations. Values that are too large will create visible jittering artifacts.
Use this setting in combination with a Spawn operator to spawn child particles at each collision point.
In order: the operator will evaluate in order with its surrounded operators.
After secondary solvers: the operator will evaluate at the end of the simulation step, after secondary solvers (bind, wobble, etc) have computed their velocities.
For accurate collisions, the operator should evaluate after secondary solvers (since those solvers may inject velocities into the simulation which will affect collisions). However, in certain circumstances you may not want the operator to evaluate after secondary solvers (if you’re using the operator to immediately send particles to another event). In that case, “in order” should be selected as the timing method.