Last update: v1.10.0 - Main page : Particle evolvers

The attractor evolver turns custom shapes into gravity sources for particles to be attracted to.
It does not perform any dynamics computations, it only stores the force to apply on the particles inside a custom field, to be used by the Physics evolver.
Usually, the attractor evolver will be used inside a Localspace evolver

Node properties

Field name	Default value	Description
General
Shape	None	The name of the shape which attracts or repels particles
ForceAtSurface	1.0	The force magnitude on the shape surface (decays as the square of the distance to the surface). Positive values attract particles, Negative values repel them.
FalloffType	`Physical`	Type of influence falloff. Physical : natural inverse-squared-distance falloff Finite : specify a max influence radius
InfluenceDistance	10.0	Distance from the attractor's surface above which the attractor has no influence anymore.
FalloffSteepness	8.0	Controls the steepness of the influence falloff curve when 'FalloffType' is set to 'Finite'
RepulseWhenInside	`false`	Repulse when inside the 'Shape'. In other words, particles are always atracted to the surface of the 'Shape' even when they're inside it.
Field customization
PositionField	`"Position"`	If this field is declared as a <float3>, it will be used as the particle position to compute the attraction force.
ForceField	`"Force"`	If this field is declared as a <float3>, it will be used to store the computed attraction force.

Auto-fields

The attractor evolver will automatically create the following particle fields:

Name	Type	Footprint	TransformMode	self access to field
Position	float3	16 bytes	Transform	read/write
name in 'ForceField' property	float3	16 bytes	Rotate	read/write

Side-effects

The attractor evolver will modify the following particle fields:

the field referenced in the 'ForceField' property

IMPORTANT: The attractor evolver will actually OVERWRITE the output 'ForceField', and will not accumulate inside it, so if you need to use multiple attractors, you'll need multiple intermediate force fields, and add them together inside a script.

IMPORTANT: you must make sure the physics evolver use the same input 'Force' field as the attractor.
For example, if you rename the default 'ForceField' property from "Force" to "MyAttractionForce", the attractor evolver will create a new particle field named "MyAttractionForce", but the physics evolver will still look for a "Force" field, therefore you must also go into the physics evolver and change its own 'ForceField' property to "MyAttractionForce".

Here is a sample of the attractor evolver running on a shape collection containing a small cube with a large mass, and a large capsule with a small mass: