/* lissajous --- plot a Lissajous curve in HPGL 2011-10-19 */

/* Copyright (c) 2011 John Honniball, Froods Software Development */

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <math.h>

#include "hpgllib.h"

void lissajous(const double x0, const double y0, const double side, const double f1, const double f2, const double theta, const int npts);

int main(int argc, char * const argv[])

{

int opt;

double xc, yc;

double h4, w4;

double maxx, maxy;

double side;

while ((opt = getopt(argc, argv, "no:p:s:t:v:")) != -1) {

switch (opt) {

case 'n':

case 'o':

case 'p':

case 's':

case 't':

case 'v':

plotopt(opt, optarg);

break;

default: /* '?' */

fprintf(stderr, "Usage: %s [-p pen] [-s <size>] [-t title]\n", argv[0]);

fprintf(stderr, " <size> ::= A1 | A2 | A3 | A4 | A5\n");

exit(EXIT_FAILURE);

}

}

/* Select first pen and draw border */

if (plotbegin(1) < 0) {

fputs("Failed to initialise HPGL library\n", stderr);

exit(EXIT_FAILURE);

}

getplotsize(&maxx, &maxy);

xc = maxx / 2.0;

yc = maxy / 2.0;

h4 = maxy / 4.0;

w4 = maxx / 4.0;

side = maxy / 3.0;

/* Split page into quarters */

moveto(0.0, yc);

lineto(maxx, yc);

moveto(xc, 0.0);

lineto(xc, maxy);

/* Draw four simple Lissajous curves */

lissajous(w4, h4, side, 1.0, 3.0, 0.0, 3 * 72);

lissajous(xc + w4, h4, side, 5.0, 6.0, 0.0, 5 * 6 * 72);

lissajous(w4, yc + h4, side, 3.0, 5.0, 0.0, 3 * 5 * 72);

lissajous(xc + w4, yc + h4, side, 7.0, 9.0, 0.0, 7 * 9 * 72);

plotend();

return (0);

}

void lissajous(const double x0, const double y0, const double side, const double f1, const double f2, const double theta, const int npts)

{

const double delta = (2.0 * M_PI) / (double)npts;

const double sintheta = sin(theta);

const double costheta = cos(theta);

const double r = side / 2.0;

int i;

for (i = 0; i <= npts; i++) {

const double t = (double)i * delta;

const double t1 = t * f1;

const double t2 = t * f2;

const double x = (r * cos(t1) * costheta) - (r * sin(t2) * sintheta);

const double y = (r * cos(t1) * sintheta) + (r * sin(t2) * costheta);

if (i == 0)

moveto(x0 + x, y0 + y);

else

lineto(x0 + x, y0 + y);

}

}