Script Controller

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Main toolbar > Curve Editor (Open) > Select a track in the Track View hierarchy. > Track View menu bar > Controller menu > Assign > Script

Graph Editors > Track View - Curve Editor > Select a track in the Track View hierarchy. > Track View menu bar > Controller menu > Assign > Script

The following Script controllers are available in the software:

Float Script - float controller
Position Script - position Point3 controller
Point3 Script - Point3 controller
Rotation Script - rotation Quaternion controller
Scale Script - scale Point3 controller
Transform Script − matrix3 PRS controller

The Script controllers work similarly to Expression controllers. They provide a Script Controller dialog where a script can be entered for computing the controller value. The primary advantages of Script controllers are:

They can use all the features of the MAXScript language, including loops, scripted functions, and path names.
Almost any property of any object in a scene can be used to help compute controller values, including mesh vertices, values of properties at arbitrary frame times, and other non-animatable properties that are not accessible in Expression controllers.
They can use MAXScript global variables to communicate and coordinate with other controllers and scripts in the software.

Refer to the MAXScript Reference for a complete explanation of this scripting language.

Writing Controller Scripts

3ds Max interprets the text you type into the Script text box as the body of a MAXScript block expression. You can type as many expressions as you want on as many lines as you want, and they are evaluated in turn. The value of the last expression is taken as the controller value. This value must yield the right type for the controller: Float for float, Point3 for position, Quat for rotation, and so on.

Because the text is inside a block expression, you can declare local variables that are visible only within the script and are temporary for one evaluation. You can also declare or access global variables that are shared with all other scripts in MAXScript and hold their values from one evaluation to the next.

A controller is always evaluated by 3ds Max with respect to a specific animation time. This might be the current time slider or incrementing frame time if an animation is playing, or a rendering is under way. In the case of Script controllers, the time being evaluated is used to establish an automatic "at time" context around the controller script, so any properties you access (outside of other explicit “at time” expressions) yield the correct values for the current controller evaluation time. This means you don't have to do anything special in your scripts to work at the correct time. You can access the evaluation time with the standard MAXScript variable, currentTime. You can also reference scene property values at other times by using "at time" expressions in your scripts, as in regular MAXScript programming.

Assign Nodes and Tracks to Variables

When you need to refer to nodes in your scene or to animation tracks, it is recommended that you use the Script controller variable toolset to create variables to assign to any particular node or controller track. This way, if you decide to later on rename your scene objects, the script controllers using these objects are preserved because the variables maintain the link to the nodes.

Otherwise, if you assign, for example, a node to a variable manually in the dialog's Expression window, that link becomes broken as soon as you rename that particular node.

Note: It is especially important to assign nodes and tracks to variables with the corresponding buttons when using XRef scenes and objects.

Procedure

Example: To keep an object centered relative to other objects in the scene during an animation:

Name the object that should remain centered foo and assign a Script controller to its Position track.
Enter foo in the Name field and click Create.

The new variable is automatically added to the Variables list.
With the variable highlighted, click Assign Node.

The Track View Pick dialog opens, listing the contents of your scene.
Expand the Objects hierarchy until you locate foo. Highlight it and click OK.

The foo node is assigned to your variable.
Enter the following script in the Script Controller dialog's Expression window:

local pos=[0,0,0]

for o in objects where o != foo do

pos += o.pos

pos / (objects.count - 1)

This script computes the average position of all objects, except the current one (written as foo here) by setting up a local, iterating over all objects except foo, accumulating a total position vector, and computing the average in the last line, which is the final result of the script.

Interface

Assigning a Script controller automatically opens a Script Controller dialog where you can enter a script. You can open the dialog subsequently by right-clicking the track on the Motion panel or in the Track View hierarchy and choosing Properties, or clicking the Properties button on the Track View toolbar.

Tip: You can resize the dialog by dragging an edge or a corner.

Create Variable group

Name—Lets you enter and edit the name of user variables.

Create—Creates a variable and adds it to the Variables list.

Delete—Removes the highlighted variable from the Variables list. You can also delete a variable by tying its name into the Name field and click Delete.

Rename—Renames the highlighted variable.

Variable Parameters group

Tick Offset—Specifies a time offset in ticks for the current variable. When the script is evaluated, the variable's value is set from the current time plus the Tick Offset value.

Note: The Time Offset has no effect on variables that are assigned a constant.

Variables List—Lists all available variables in the controller. The following pre-defined constant variables are available in every script Controller and cannot be deleted or renamed:

F—the current time in frames
NT—the normalized time
S—the current time in seconds
T—the current time in ticks

Assign Constant—Opens a dialog which lets you assign a constant to the highlighted variable.

Value expression—Enter any MAXScript value (such as an integer, a float, an array, etc.) or expression.

Value expression result—Displays the results of the expression above.

Evaluate—Analyzes your expression at the current time.

OK—Assigns the value expression result to the current variable.

Cancel—Disregards the current value expression result and closes the dialog.

Assign Track—Lets you assign a controller to the highlighted variable. The controller's value is taken at the current time plus the variable's Tick Offset.

Assign Controller—Lets you assign a track to the highlighted variable.

Assign Node—Lets you assign a node to the highlighted variable.

Expression text field—Enter the script expression here to calculate the controller value.

Description text field—Enter comments regarding the functionality of the controller.

Load/Save—Load and save scripts to text files.

Debug—Opens the Script Controller Debug Window, which displays the value of all variables used in your script.

Evaluate—Evaluates the script expression. The evaluation is computed for the current position of the time slider.

Close—Compiles and checks the controller script for errors. If no errors are found, the dialog is closed. Any problems result in a query box asking whether you want to revert the expression to the original value of the current track and close the dialog (OK), or to return to editing the expression (Cancel).