This tutorial will show you the differences between the Expression Editor, Script Editor, and History Window; as well as introduce you to the use of TCL procedures.

This tutorial requires:

Pixels3D | studio | v3.x

The Expression Editor evaluates the script it contains everytime the frame changes, the user modifies the scene, or a redraw occurs.

This has a toggle in the Scripts Menu. When Constant Script Evaluation is on, the expressions are executed when specified above.

Selecting the menu item again will turn it off, meaning no expressions will be evaluated unlesss you choose Run All Now, in which case they will be evaluated once.

The Script Editor only evaluates a script when the Run item is chosen from the menu on the right of the window.

Note that the Script Editor does not retain the script it holds when it is closed. It is merely a temporary space to format & edit tcl scripts without them being involuntarily executed before they're finished.

It has the ability to set a Scene Script. A Scene Script is a script that is evaluated only once - when the scene is opened. This is useful for holding TCL procedures that would otherwise clutter the Expression Editor.

The History Window is mostly self-explanatory. The PixelScript Syntax for everyt action you perform appears in the top portion of the window.

The lower portion of the window can be used as a TCL Console. Simply enter TCL commands, and press the return key to execute them.

A TCL Procedure is similar to a Function or Subroutine in other programming environments.

It is declared with the proc command.

The example on the right shows a simple TCL Procedure called SpinX. It spins an object on the x axis at a user-defined speed.

There are two parameters to the procedure - object, and speed. These are specified in curly brackets following the procedure name.

Once the TCL procedure has been evaluated, its functionality can be called by the procedure name, followed by the parameters. The Expression on the right uses the TCL procedure SpinX.

If we were to save the scene with spinning objects, when we opened it again, the objects would not spin, and there would be an error in the history window.

This is because the Procedure has not been added to the TCL command list. To make this work, we'll use a Scene Script.

Create a Sphere.

Open both the Script Editor ( CMD-2 ), and the Expression Editor ( CMD-1 ).

In the Script Editor, choose Set Scene Script.

Save the Scene File.

The next time you open the file, the TCL Procedure will execute, and the Expressions using the Procedure will work.

The Get Scene Script menu item allows you to retrieve & edit the Scene Script.

Now that you know what should go where and why, the scripting interface to Pixels should spark some ideas for your own scenes.