9

Expression Controller 323
Tip:
You can resize the dialog by drag ging an edge
or a corner.
Create Variables g roup
Name—Thevariablename.
Scalar /Vector—Choosethetypeofvariableto
create.
Cr e ate —Createsthevariableandaddsittothe
appropriate list.
You must enter a name and specify a type b efore
clicking Create.
Delete—Deletes the highlighted variable in the
Scalar or Vector list.
Rename—Renames the highlighted variable in the
Scalar or Vector list.
First highlight the variable in the list; this places
thenameintheNamefield.Editthenameinthe
Name field, and then click Rename; the new name
replaces the previous one in the list.
Variable Parameters group
Tick Offset—Contains an offset value.
A tick is 1/4800 of a second. If a variable has a
non-zero tick offset, that value is added to the
current t ime.
Expression group
Type an expression in the E xpression box.
The expression must be a v alid mathematical
expression. The result is either a three-value vector
for a vector expression (p osition, scale, or point3)
orascalarvalueforafloatexpression.
Description group
Type text in this group to document an expression.
For example, you can describe user-defined
variables.
Funct io n 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.
Loa d—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 al l variables,
and the value of the expression. When you
change the variables or move the t ime slider,
the Debug window automatically updates so
you can interactively view what’s happening
w ith the expression. The values for fr ames (F),
normalized t ime (NT), secs (S), and ticks (T) are
also displayed.
Eva luate—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 er ror
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 actu ally is, unless the
problem is that opening and closing parentheses
(orthebracesforvectors)don’tmatch. Inthis
case, evaluation c an proceed further before the
error is detected.
Clo se—Closes the Expression Controller dialog.