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Expression group
Type an expression in the Expression box.
The expression must be a valid mathematical expression. The result is either
a three-value vector for a vector expression (position, scale, or point3) or a
scalar value for a float expression.
Description group
Type text in this group to document an expression. For example, you can
describe user-defined variables.
Function List Displays a list of Expression controller functions.
In the list, p, q, and r represent scalar values or scalar expressions; V and W
represent vector values or vector expressions.
Save Saves an expression. Expressions are saved as files with a ..xpr file name
extension.
Load Loads an expression.
A saved expression does not include variable definitions or values. After loading
the expression, you need to redefine them.
Debug Displays the Expression Debug window.
This window shows the values of all variables, and the value of the expression.
When you change the variables or move the time slider, the Debug window
automatically updates so you can interactively view what's happening with
the expression. The values for frames (F), normalized time (NT), secs (S), and
ticks (T) are also displayed.
Evaluate Evaluate the expression for each frame in the animation.
There is no explicit assignment (= or := operator) as in a conventional
programming language; the assignment is implicit and takes place over time.
If the expression has a syntax error, an error message is displayed. The error
message is the first part of the expression itself. The last character in the error
message is the point of the error. This is usually where the error actually is,
unless the problem is that opening and closing parentheses (or the braces for
vectors) don't match. In this case, evaluation can proceed further before the
error is detected.
Close Closes the Expression Controller dialog.
3160 | Chapter 15 Animation