Anatomy of a Rule

Learn about the base requirements to structure a Rule script.

Note

To compose a Rule script, you must use the Lua scripting language.

Minimum functional Rule structure

To compose a basic functional Rule, you minimally have to specify two complementary statements, each represented by a code line:

  1. A statement that defines the Rule, which includes the definition of a user control.
  2. A statement that sets the model property value you want to manipulate with the user control.

The first statement outputs a variable value that the second one uses as an input. You can additionally process the variable value in between, if needed.

Rule definition

Here's the generic syntax of a statement that defines a Rule and its user control.

<variable_name> = <rule_definition_function>(<rule_name>, <reference_values>)
Key element Description
<variable_name> The name of the variable that holds the value controlled by the Rule.
<rule_definition_function> The function that defines which type of control to use in the UI (slider, checkbox...) Several rule definition functions are available.
<rule_name> The name of the Rule, and optionally the name of its grouping category, in the UI.
<reference_values> Static values that frame the Rule according to its type, including default values.

Property value setup

Here's the generic syntax of a statement that sets a model property value to manipulate.

<property_value_setup_function>(<target_property_identifiers>, <input_parameters>)
Key element Description
<property_value_setup_function> Function to specify which type of property setup to perform. Several property value setup functions are available.
<target_property_identifiers> Parameters to specify which property of which object to control with the Rule.
<input_parameters> Parameters to set the property value according to the variable <variable_name> controlled by the Rule.

Additional resources