pds@tove (Dave Stotts) (04/17/87)
For you recreational computing fans, here is a program to waste
some time with. Sorry if this is a rehash of some earlier posting,
but it has been going on a year since the Scientific American article
came out, so many readers may have missed any eariler version(s).
It draws nice stuff on your raw sun screen.
The figures look like lace doilies, or oriental rug patterns, or when
magnified, fine cell structure and other biological wonders.
Try these arguments for fun:
hop 5 13 1400 (default)
hop 30 20 10 (good at mag 4)
hop 0.3 1.5 12
hop 12 0.9 124
hop 14 0.9 124
hop -12 -3 -45 (good at mag 4)
hop 16 1.333 121
Hop.c has compilation info in the header comment.
Enjoy.
Dave Stotts
Univ. of Maryland CS Dept.
pds@leviathan.cs.umd.edu
=========================================================================
/*
* hop.c adapted from scientific american, 9/86, p.14+
*
* version for Sun-3 use.
*
* cc -w -O -o hop hop.c -lm -lpixrect
*
* arguments: a b c magx center limit
* a, b, c are parameters of the equation
* magx (==magy) allows blowing up the image to reveal fine structure
* center allows the image to be shifted on the screen
* (useful when magnifying)
* limit is number of points to plot
*
* all arguments have defaults
*
* note the defines for color screens.
* you may have to change the dev name in the open statement.
*
*/
#include <stdio.h>
#include <pixrect/pixrect_hs.h>
#define MARGIN 3 /* offset from side of sun screen */
#define COLOR 1
/* for color screens... this colors a point according to the number
of iterations it takes to get to the point in the sequence.
the multiplier is to slow down the color changes, and the mod'ing
is to keep it in the palette
#define NUMCOLORS 256
#define DELTACOLOR 10
#define COLOR ((((k/NUMCOLORS)+1)*DELTACOLOR)%(limit/NUMCOLORS))
*/
main(argc,argv)
int argc;
char **argv;
{
double atof(), sqrt(), fabs();
double i,j,inew,jnew;
double a = 5.0;
double b = 13.0;
double c = 1400.0;
int k, limit=100000, center=400, magx=1, magy=1;
struct pixrect *pr;
FILE *fp;
if (argc > 1) {
a = atof(*++argv);
b = atof(*++argv);
c = atof(*++argv);
}
if (argc > 4) {
magx = atoi(*++argv);
magy = magx;
}
if (argc > 5) {
center = atoi(*++argv);
}
if (argc > 6) {
limit = atoi(*++argv);
}
pr = pr_open("/dev/fb");
pr_rop(pr,0,0,pr->pr_size.x - 1,pr->pr_size.y - 1, PIX_CLR,NULL,0,0);
i = j = 0.0;
for (k=0; k<limit; k++) {
pr_put(pr, (int)(i*magx)+center+MARGIN,
(int)(j*magy)+center+MARGIN,
COLOR );
inew = j - (i<0?-1:1) * sqrt(fabs(b*i - c));
jnew = a - i;
i = inew;
j = jnew;
}
}