Propagation Operator
The Propagation operator grows new strands out of existing strands. Rather than cross-referencing separate objects, it spawns child strands directly along the strands already in the groom. Stacking several propagation operators builds hierarchies of strands, which makes it ideal for feathers, branching plants, trees, and similar structures.
Strand groups and hierarchies
Propagation works hand in hand with strand groups. Each propagation step takes two group settings: which group of strands to grow on, and which group to assign to the new strands. By assigning a different group at each level you can later style each level independently.
For example, to build a tree: keep the trunk in group 0, propagate branches onto group 0 and assign them group 1, then propagate leaves onto group 1 and assign them group 2. Afterwards you can target each group with its own styling and width operators.
Distribution along strands
You control where and how many child strands appear:
- The generation method decides how new roots are placed along each base strand - randomly by default, or uniformly, or per vertex.
- A per-strand count sets how many children each base strand produces.
- A randomness setting adds variation to otherwise uniform placement.
An optional per-strand channel can record each child's root position along its base strand (from 0 at the root to 1 at the tip), which you can use to drive other effects. See Working with Strand Channels.
Related
- Scatter Operator copies a separate reference groom onto strands, which complements propagation for instancing shapes such as feathers.
- Multiplier Operator multiplies strands at their existing roots to add density.