TangentCircles Screen Saver

This screen saver draws circles onto your computer's screen. Each circle is drawn touching a circle that was previously drawn.


image of TangentCircles preference pane
TangentCircles Preferences

In this screen saver there are two basic parameters available to you, "Speed" and "Erase Screen".

"Speed" controls the screen saver's attempted frame rate and ranges from 10 to 100 frames per second. Of course, the actual frame rate achieved will depend upon your computer's ability to keep up. As such, you may not be able to get a full 100 frames per second even if you request it. Setting the speed lower will use less CPU, which may be important if you are running background processes such as [email protected] or a web server. The default setting is 75 frames per second.

"Erase Screen" controls how often the screen will be erased to solid black. The circles appear in groups of approximately 200 circles. This setting will cause the screen to be erased after as few groups as one ("Often") or as many as 50 groups ("Seldom") have been drawn. The default is to erase the screen after 18 groups have been drawn.


The Tangent Circles screensaver module is based on a module written by Larry Cordner for NEXTSTEP's BackSpace screen saver program.

The original module, "TanCircleView", used an algorithm which came from Sam Hobbs' code in his article in the September 1991 issue of the C User's Journal (p. 122, 125). The article was a review of the book Computers, Pattern, Chaos, and Beauty by Clifford A. Pickover, published in 1990 by St. Martin's Press. Sam's code was based on an algorithm from Pickover's book.

The basic algorithm has survived the port from NEXTSTEP essentially unchanged. We have given the module new options and features, tuned it to look great on Mac OS X, and based the new Objective-C code upon Apple's Quartz and Cocoa technologies.