Computer art for the Tektronix 4052. Joe Jacobson.

Computer Art for the Tektronix 4052

In this article I describe my Corsage program. The name stems from the patterns generated, which remind me of assemblages of ribbons and flowers. A Basic source listing and some sample output pictures accompany the text.

This program is a further generalization of my Sinusoidal Loop Programs No. 1 and 2 (Creative Computing, January and March, 1983). However, it uses only one polar coordinate function. This function is used to compute the radius as the absolute value of a weighted sum of sinusoids. These sinusoids are, in turn, functions of the angle (A).

An important innovation, which was suggested by my engineering coworker Stuart Boose, is that the angular frequency coefficient L is itself a function of the angle. I used the same type of angular function for L as for the radius. This function itself has an angular frequency coefficient, K, which is entered from the keyboard.

Both the radius function and the L function use the same amplitude coefficients as weights for the sinusoids. These are designated as S and T and are entered from the keyboard.

There are three other parameters that are entered from the keyboard. These are D, G, and T1. D is the increment added to the radius between successive angular sweeps. G is the increment in the angle during an angular sweep. T1 will be discussed below.

When you run the program it places prompts on the screen, asking you to enter values for D, S, T, K, G, and T1. If you enter a 1 for T1, the picture will be plotted and a list of input parameter values will appear below it. Then you clear the screen and hit RETURN, and the same picture will be plotted again without the parameter list. This way you can make hardcopy prints with and without parameters and keep a convenient record of which parameter combinations make good pictures. If you don't want a parameter listing at all, enter a 2 for the value of T1.

Table 1 lists recommended ranges of the values of the input parameters. Values in these intervals seem to give the best results in most cases. However, other values may also yield good pictures; you should experiment with the program to find out which values to use. The parameters D, S, T, K, and G do not have to be integers; decimal fractions like K=29.2 can also work well, and this increases the number of different pictures you can make.

I hope you like the corsage designs. I will describe the other polar coordinate computer art programs I have recently written, in future issues of Creative Computing.

Table: Suggested Parameter Values.