Introduction
After my book, "Inside Softimage", published by New Riders publications, was released during Siggraph 1998, readers have been asking me over and over again for a comprehensive and comprehensible explanation of expressions in Softimage 3D. I quickly realized that people all over the world were dying for more information on this crucial area of functionality. Expressions fascinate people because they hold out the promise of huge productivity gains and tremendous improvements in quality of work, all with very little effort. Expressions can in fact be used to automate just about everything in Softimage 3D. Expressions can be used to create custom controls to simplify the tasks of animation. Expressions can make animation decisions and change parameters for you. Expressions can easily calculate complex mathematic and trigonometric functions and apply the results to precisely animate objects in your scene.
Expressions can be used to add in physical rules to a scene, and pre-defined behaviors to characters. Expressions can even turn Softimage 3D into a real-time game simulation tool. But there«s a catch - expressions are just what they sound like: mathematical formulas. Many artists fear math, and so shun expressions, even when the alternative is a lot of tedious and repetitive hard labor. Perhaps the reason non-technical people have such a hard time with expressions is that there has never been a sensible explanation of their use in Softimage 3D. The manuals, although complete, are almost unintelligible, having been written in EBNF notation familiar only to programmers. I will take some of the mystery out of expressions, and document a few ways to use them. The rest is up to you - learn from examples, then branch out and design your own expressions to do cool new stuff.