XGen Expression Editor

The Expression Editor lets you create new expressions or apply XGen sample expressions that control the placement, behavior and appearance of primitives. To open the XGen Expression Editor, click the icon located beside attributes in the XGen Window tabs. For XGen expression technical documentation, see XGen Expressions.

The XGen Expression Editor has the following main areas:

Expression Editor tabs

Click the Library or Samples tab to display pre-authored expressions. Select an expression from the list to apply it the selected Primitive attribute. Type keywords in the search area at the top of the expression list to find expressions containing your keyword.

These tabs are customizable. You can add new tabs by creating new subdirectories in global, local, and user folders. For example, the Library and Sample folders generate from the following location when the XGen Expression Editor is opened:

C:\Program Files\Autodesk\Maya2014\plug-ins\xgen\presets\expressions\library C:\Program Files\Autodesk\Maya2014\plug-ins\xgen\presets\expressions\samples

Expression swatch

Depending on the type of expression you are working with in the Expression Editor, the swatch displays:

A visual representation of the expression's output as the attribute values change. Clicking the swatch updates the image shown, which provides a preview of the expressions. If there are sliders in the expression the update is automatic and interactive
For example, you can change the attribute values of a Noise expression and see the representation of the noise pattern created by the expression.
Red when an expression fails to evaluate. Click the swatch to display the expression errors.

Expression value controls

Use the sliders to set the attribute values used by the expression. You can also type these values in the expression text field.

Expression text field

The text field displays all of the components used in the expression. Use the sliders to set the attribute values used by the expression. You can also type these values in the expression text field.

The text field area in the XGen Expression Editor provides the following syntax support features:

Syntax highlighting that uses the following color conventions.

Expression component	Text color	Example
Comments	Red
Variables	Green
Functions	Cyan
Numeric values	White
Constants	Orange
File paths and strings	Yellow

Text auto-completion for functions, variables, and constants. As you type in the text field, a suggested code displays in a list.
To display the auto-complete or tip window of an existing function, place the cursor on the function and press + .

After you select expression text from the list, a pop-up window provides a tip on the function, variable, or constant.

Expression Editor commands

When creating or editing expression, you can use the following commands:

Accept: Returns the current expression and assigns it to the expression control, but does not save it to disk.
Save: Saves the current expression (.se) file to the User folder. If the expression does not already exist, the Save Expression window opens, which lets you specify a name and location for it.
Save As: Opens the Save Expression window opens, which lets you specify a name and location for the expression.
Cancel: Cancels the current expression editing session.

NoteNavigating the expression tree can trigger file saves if the current expression is being edited.