...open.
Some readers may wonder why ``eye closedness'' is a positive attribute while ``mouth openness'' (rather than ``mouth closedness'') is as well. This is because I have assumed positive attributes to be differences from a ``neutral'' expression, and this expression to have the mouth closed and the eyes open.
...axes,
In the geometry used, the X axis is the horizontal axis across the screen, the Y axis is the vertical axis and the Z axis is the axis going outward from the screen.
...face).
These are the two degrees of freedom afforded by Parke's model, on which the 3-D rendering code used is based, and they give more expressiveness than one degree of freedom.
...left
The convention used for denoting the sides of the face is to use the sides from the face's point of view; thus, the left eye is the one on the right-hand side of the face as seen by the user.
...expansion.
This parameter corresponded to mouth scale in the 2-D model. It is left unused since there is no satisfactory way to implement it using the Parke's model rendering code.
...unselected
The reason why unselected facial expressions are mutated, rather than selected ones, has to do with the interface; the cue is that selected facial expressions are the ones which the user is interested in, and thus should be preserved.
...face.
The PostScript language is stack-based; data is usually passed on a stack known as the operand stack. Procedures are known as operators, and operate on the data on the stack.
...she
When referring to a user of indeterminate gender, I shall use the pronoun, ``she'', as there is not yet a widely-accepted gender-neutral pronoun and longer constructs such as ``he or she'' are cumbersome
...browsers.
CGI stands for ``Common Gateway Interface'', and is a technique which allows interactive programs producing text and graphics to be accessed over the World Wide Web.
...faces,
There was an option to display the faces in three-dimensional form, but this was not used as a default, because this interfered with the local display of the workstation on which the Web server ran.
...evolve.
This is not always the case during casual experimentation, although it would be during serious use.
...expressions.
If only one expression is selected, it is, of course, its own average.
...transformations
I use the term ``linear transformation'' to denote a transformation between facial expressions in which all attributes change at a constant rate, and which, if plotted against time, would be drawn in a straight line.

Andrew C Bulhak
Tue Nov 7 11:44:11 EST 1995