Effectors

Effectors bring the outside world into the simulation.
They expose forces like gravity, light-seeking, or collisions as attributes, so that Grow and other nodes can respond dynamically.

What Effectors Are

• Attributes sampled in world space.
• Plugged into sockets on nodes like Grow.
• Used in combination with Mappings to translate raw vectors or scalars into parameter changes.

Effectors don’t change geometry directly — they provide guidance signals.
It’s still up to mappings and simulation logic to decide how those signals are applied.

Why Use Effectors?

Without effectors, plants grow in isolation: uniform and predictable.
With effectors, plants:

• Lean toward light (phototropism).
• Bend under gravity.
• Spread or compress based on balance.
• Respond to collisions with nearby geometry.

Effectors add context and environmental realism.

How Effectors Work in Simulation

During Simulate:

1. Effector vectors or scalars are computed.
2. They are passed into sockets (e.g. Bend, Pitch, Width).
3. A Mapping chain converts the effector into parameter changes.

This means effectors are never hardwired — they’re always interpreted through mappings.

Types of Effectors

Gravity Effector

• Provides a vector pointing down.
• Commonly mapped into bend or orientation.

Phototropism Effector

• Vector pointing toward a light source.
• Drives bending, fork direction, or cluster distribution.

Balance Effector

• Vector derived from the plant’s overall weight distribution.
• Helps stabilize shapes (reducing unrealistic drift).

Collision Effector (experimental)

• Vector feedback from nearby geometry.
• Allows branches to deflect instead of penetrating.

Using Effectors

• Plug an effector into a socket (e.g. Bend Strength).
• Use a Map to control how strongly it influences growth.
• Combine multiple effectors: e.g. gravity + phototropism blended together.

Example Workflows

• Weeping willow effect — Gravity effector mapped into downward spiral pitch.
• Sun-seeking shoots — Phototropism effector drives fork orientation.
• Stable trunk — Balance effector reduces lean at higher ages.
• Tree vs wall (experimental) — Collision effector pushes branches outward when geometry is nearby.

Notes

• Effectors are evaluated per growth step, not globally.
• Multiple effectors can feed into the same parameter through blended mappings.
• Collision effector is slow at high point counts and will improve in later versions.