Faces 2.0

15 May 2001

What is Faces?

Faces 2.0 is a screensaver module for Mac OS X that generates and displays random Chernoff faces. It evolved from an After Dark module I first released in 1995. The original face-generation routine was based on code by Dave Johnson in Apple's develop magazine #6 (which was in turn based on Clifford Pickover's Chernoff face routine in his book Computers, Pattern, Chaos, and Beauty). Faces 2.0 has been re-written from the ground up in Cocoa.

Where Can I Get Faces?

Faces is available for download at:

http://bradandkathy.com/files/FacesSaver2.0.dmg

So What's a Chernoff Face, Anyway?

Chernoff faces are simplified, cartoon-like faces that can be used to graphically display complex multivariate data. They draw upon the human mind's innate ability to recognize small differences in facial characteristics and to assimilate many facial characteristics at once. Each of several variables is assigned to a facial characteristic and a face is then generated for each condition. The method was developed by the statistician Herman Chernoff and presented in a 1973 paper in the Journal of the American Statistical Association titled The Use of Faces to Represent Points in k-Dimensional Space Graphically. If you want to know more about Chernoff faces, I encourage you to find this article. Although academic, it is quite readable by those without a background in statistics. Professor Chernoff is now Professor Emeritus of Applied Mathematics at MIT and of Statistics at Harvard University. His web page is here.

The faces drawn by the Faces module vary in the eleven characteristics shown below. In addition, the faces also vary in size, location, and color.

Interesting Tidbit

In the appendix to Professor Chernoff's 1973 article, he mentions: "At this time the cost of drawing these faces is about 20 to 25 cents per face on the IBM 360-67 at Stanford University using the Calcomp Plotter. Most of this cost is in the computing, and I believe that it should be possible to reduce it considerably."

Why Do So Many of the Faces Look Unhappy?

Good question. When I wrote the original AfterDark version of Faces, I wondered the same thing and for a time thought something might be wrong with my code. After a bit of testing, I confirmed that the faces were essentially random. I can only assume that the human face, as approximated by a Chernoff Face, is capable of making many more unhappy expressions than happy ones. Perhaps a psychologist could clue us all in.

Installation

To be recognized by the screen saver in Mac OS X, Faces must be installed in one of the /Library/Screen Savers folders. To allow Faces to be used by all users on a computer, drag Faces.saver to /Library/Screen Savers (you may have to create the "Screen Savers" folder). To use Faces on a single user account, drag Faces.saver into the Screen Savers folder inside the user's own Library folder (/Users/Username/Library/Screen Savers). In recent versions of Mac OS X, you can install Faces by simply double-clicking on it.

Settings

Faces provides three preference settings to customize its drawing. To change the settings, click the "Configure" button in the Screen Saver pane of System Preferences.

Color Scheme: This setting allows you to choose the color palette Faces uses for drawing. There are currently seven options: Bright, Dark, Pastel, Primary, Grayscale, Black & White, and Random.

Speed: Controls how quickly new faces are added to the screen. Ranges from one every two seconds to as fast as possible.

Size: Controls whether faces are all drawn at a single fixed size or at random sizes.

Compatibility

Faces should work fine on any Macintosh capable of running Mac OS X, including those with multiple monitors. If you encounter problems with Faces, please let me know at the e-mail address below. Faces 1.3, which runs on Mac OS 9 and earlier using After Dark or Darkside is also available.

Change History

2.0 (15 May 2001)

First Mac OS X release.

Freeware

Faces is freeware. You may use Faces for as long as you want for free. You may distribute Faces in any way you wish as long as you don't charge for it (not including normal connect-time download charges) and you distribute only the complete distribution, including documentation. You may not distribute this program on any disk costing more than $5 or on CD-ROM without my explicit permission.

Disclaimer

Bradley D. Mohr disclaims all warranties relating to this software, whether express or implied, including without limitation any implied warranties of merchantability or fitness for a particular purpose. Bradley D. Mohr will not be liable for any special, incidental, consequential, indirect, or similar damages due to loss of data or any other reason, even if Bradley D. Mohr or an agent of his has been advised of the possibility of such damages. In no event shall Bradley D. Mohr be liable for any damages, regardless of the form of the claim. The person using the software bears all risk as to the quality and performance of the software. Because some states do not allow the exclusion or limitation of liability for consequential or incidental damages, the above limitations may not apply to you. Do not taunt Happy Fun Ball.

Copyright

Contacting the Author

I always enjoy getting comments about Faces, whether good or bad. Send comments or suggestions to bdm@sprylo.com.