/* doily.c:
Draws a doily depending on how many points you give it (range is currently set between 3..100). point count is equivale nt to how many line segments make up the circle's edge. */
#include <gl/gl.h> #include <gl/device.h> #include <math.h>
#define PI 3.1415926535
float points[100][2];
main(argc, argv) int argc; char *argv[]; {
int val,dev; long numpts; /* First figure out how many points there are. */
if (argc != 2) { printf("Usage: %s <point_count>\n", argv[0]); exit(0); }
numpts = atoi(argv[1]); /* convert argument to internal format */ if (numpts > 100) { printf("Too many points\n"); exit(0); } else if (numpts < 3) { printf("Too few points\n"); exit(0); }
initialize(numpts); while (TRUE) { if (qtest()) { dev = qread(&val); if (dev == ESCKEY) { gexit(); exit(0); } else if (dev == REDRAW) { reshapeviewport(); drawdoily(numpts); } } }
}
initialize(numpts) long numpts; {
int gid; long i; /* Now get the x and y coordinates of numpts equally- * spaced points around the unit circle. */ for (i = 0; i < numpts; i++) {
points[i][0] = cos((i*2.0*PI)/numpts); points[i][1] = sin((i*2.0*PI)/numpts); } keepaspect(1,1); prefposition(XMAXSCREEN/4,XMAXSCREEN*3/4,YMAXSCREEN/4, YMAXSCREEN*3/4); gid = winopen("doily"); qdevice(ESCKEY); qdevice(REDRAW); qenter(REDRAW,gid); ortho2(-1.2, 1.2, -1.2, 1.2);
}
drawdoily(numpts) long numpts; {
long i,j;
color(BLACK); clear(); color(RED); for (i = 0; i < numpts; i++) for (j = i+1; j < numpts; j++) { move2(points[i][0], points[i][1]); draw2(points[j][0], points[j][1]); }
}
/* Changes: - exit(); to exit(1); */
The keepaspect subroutine, prefposition subroutine.