Grow operator

The Grow operator invokes a Diffusion-Limited Aggregation (DLA) algorithm to spawn new particles close to existing particles in an outward-growing fashion.


Growth Rollout

Growth

  • Radius: controls the size of particles within the DLA algorithm. Increasing this value will increase the overall size of the growth.

As particles are spawned, they are connected to each others’ implicit surfaces. The minimum distance between two spawned particles is therefore (radius x 2).

  • Enable spacing: controls whether to use a custom value for the minimum size of empty space required for that region to spawn particles. If this is disabled, the radius value will be used instead.

  • Spacing value: the minimum size value of an empty region before it will be able to spawn particles. Increasing this value will result in growths stretching outward, rather than remaining in tighter clumps.

Each time the growth algorithm progresses, it chooses a random region adjacent to existing particles and checks that region for overlapping particles. If a particle exists inside the region, spawning inside the region is disabled. The smaller the spacing value, the easier it is for the growth algorithm to find empty regions and therefore progress forward. The larger the region, the more the growth algorithm must stretch out into empty space in order to find an area free of particles.

  • Bias: controls whether the search algorithm will tend to look for valid regions near the center of existing particles, or near the boundary of existing particles. Values less than 1.0 bias towards the center, values greater than 1.0 bias towards the boundary.

  • Inherited vel %: the percentage of velocity child particles will inherit from their parent.

  • Max tries: the maximum number of attempts the algorithm will make to find a valid region of space to spawn a particle, at each growth iteration.

  • Iterations: the number of growth iterations to perform, at each time step of the simulation.

  • Align rotation: aligns the rotation of particles to the vector between themselves and their parent.

  • Affect position/velocity: chooses which particle properties the growth algorithm will affect.

Clusters
  • Enable clustering: controls whether the DLA algorithm will iterate over clusters of particles individually, or over all event particles simultaneously.

  • Channel: the custom particle data channel from which cluster data will be retrieved.

By default, the growth algorithm will process all event particles together. By enabling clustering, you can separate particles into cluster-specific groups, which causes the growth algorithm to process those groups separately. This allows you to have multiple, independent growths forming within the same event.

Seed position

  • Growth bounds/random particle: controls whether starting candidate positions for new growth particles will be located around the bounds of overall growth, or at a random particle within the growth.

  • Spread: the amount of random spread applied to the seed positions.

  • Simulation groups: controls which particle simulation groups the random particle seed position will be derived from.

  • Show seed points: displays the resulting seed points in the viewport.

Uniqueness

  • Seed: the seed value for all varied parameters.

Forces Rollout

Forces will affect the direction of growths.

Forces

  • Force object list: the list of force objects used to direct the growths.

  • Influence %: the amount of influence forces will have on growths.

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

Built-in Force

Using the built-in force allows you to apply simple forces to growth particles without having to create force objects in the scene.

  • X/Y/Z: the direction vector of the built-in force.

  • Strength: the strength of the built-in force.

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

Objects

  • Object list: the list of scene objects which will act as growth attractors.

  • Attraction: the amount of attraction force the scene objects will apply to particles.

  • Above/Below: controls whether attraction forces will be applied to particles above or below the object’s surface.

Attraction influence

The attraction influence extends outwards from nearby objects.

  • Distance: particles within this distance will be fully affected.

  • Falloff: the effect on particles beyond the base distance, but within this falloff distance, will diminish according to the inverse-square law.


  • Follow: the amount of force the scene objects will apply to particles, parallel to the object’s surface.

  • Above/Below: controls whether follow forces will be applied to particles above or below the object’s surface.

Follow influence

The follow influence extends outwards from nearby objects.

  • Distance: particles within this distance will be fully affected.

  • Falloff: the effect on particles beyond the base distance, but within this falloff distance, will diminish according to the inverse-square law.


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