set_environment_attribute_value ‐ Dynamic modification of the environment parameters
This action is used to modify the values associated with attributes in a environment element. If the attribute values contain parenthesized expressions, they are dynamically evaluated as numerical expressions and their values are replaced in the attribute value strings. The string value of the operator attribute is an operator string. The values of the operator must be "=", "=", "+=", "-=", "*=", or "/=". The child node is a possible child of a environment element that contains at least one attribute and its associated value. The currently supported children of environment elements are referenced in the environment node definition.
The attributes of the child node are called source attributes. The target node must be an environment element. This environment element is called the target environment. In this case, the values of the source attributes are used to modify the values of the corresponding child element in the target environment.
For instance if the source element is a display element that contains the attribute echo, and if the operator is "=", the source value replaces the echo attribute in the display element of the target environment. The other operators respectively correspond to addition, substraction, multiplication, and division of the target values by the source values. The attributes of the target display element that are not instantiated in the source element (the child node) are not modified by this action.
The following element must occur in set_environment_attribute_value: one child node of an environment element.
The target node must be an environment node.
The example below defines an action that sets the value of the echo to 0.0758704.
<set_environment_attribute_value operator="="> <display echo="0.0758704"/> </set_environment_attribute_value>