Variable Setters

Technical reference for user-defined global variables.

Variable Setters are used to create global custom variables within a craft. They allow for centralized logic and state management that can be accessed by any expression on the aircraft. Every variable setter in the list is evaluated once per physics tick.

Configuration

In the aircraft’s XML file, variable setters are defined within the <Variables> tags. Each setter follows a specific structural format:

<Setter variable="Name" function="Expression" priority="0" activator="Condition" />

The order in which setters appear in the XML file matches their order in the in-game Variable Setter GUI.

Properties

  • variable: The unique name of the variable.
  • function: Any valid Funky Trees expression used to calculate the variable’s value.
  • activator: An optional Boolean expression that determines if the setter is active. If not specified, the setter is always active. When the expression evaluates to false, the setter is ignored.
  • priority: A numerical value used to determine precedence. By default, this is 0, but it can also take negative integers. If multiple setters target the same variable name, the active setter with the highest priority value controls the final output.

Examples

Priority Ranking

Demonstrating how multiple active setters are resolved based on their priority level.

  • Setter 1: variable="Mode" function="1" priority="-1"
  • Setter 2: variable="Mode" function="2" priority="0"
  • Setter 3: variable="Mode" function="3" priority="5"

If all three setters are active, Mode will evaluate to 3 because Setter 3 has the highest priority. If Setter 3 is disabled via an activator, the value will fall back to 2.

Activator State Control

Demonstrating how the activator field determines whether a setter participates in the current tick’s evaluation.

  • Setter 1: variable="Autopilot" function="TargetHeading" activator="Activate1"
  • Setter 2: variable="Autopilot" function="0" priority="-1"

In this setup, when Activate1 is true, Setter 1 is active and provides the TargetHeading. When Activate1 is false, Setter 1 is ignored entirely, and the variable falls back to the low-priority default of 0 provided by Setter 2.

Technical Resolution

  • Global Access: Variables defined here are global. They are called directly by their name in any part expression on the craft.
  • Evaluation: The entire list of variable setters is evaluated every tick; the update frequency is determined by the game physics quality setting.