At compile-time, macro-Commands can be used to facilitate the design of repetitive scene. These commands are interpreted during the compiling of the scene graph. They are purely syntactic and do not enhance VC language's semantics. Repetition and set commands control parameter values. These commands are described in Chapter 4.
At run time, the execution of scripts and dynamic animations, such as interpolations or path-based motions, can be controlled by variables. Variables are set by script commands and are read in any string or arithmetic expression. They are also used by script control commands for boolean testing. There are three types of variables (scalars, tables, and matrices); they are described in Chapter 4.