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reuleaux.c
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reuleaux.c
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/* reuleaux --- draw some Reuleaux polygons 2020-09-05 */
/* Copyright (c) 2020 John Honniball, Froods Software Development */
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <unistd.h>
#include <math.h>
#include "hpgllib.h"
void plot_ul(const double x0, const double y0, const double width, const double height, const double r1, const double r2);
void plot_ur(const double x0, const double y0, const double width, const double height, const double r1, const double r2);
void plot_ll(const double x0, const double y0, const double width, const double height, const double r1, const double r2);
void plot_lr(const double x0, const double y0, const double width, const double height, const double r1, const double r2);
void reuleaux(const double xc, const double yc, const double r, const int n, const bool drawSides);
int main(int argc, char * const argv[])
{
int opt;
double xc, yc;
double maxx, maxy;
double r1; /* Radius of smaller arcs */
double r2; /* Radius of larger arc */
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;
r1 = maxx / 5.0;
r2 = maxy / 5.0;
/* Split page into quarters */
moveto(0.0, yc);
lineto(maxx, yc);
moveto(xc, 0.0);
lineto(xc, maxy);
/* Draw four Reuleaux polygons */
plot_ll(0.0, 0.0, xc, yc, r1, r2);
plot_lr(xc, 0.0, xc, yc, r1, r2);
plot_ul(0.0, yc, xc, yc, r1, r2);
plot_ur(xc, yc, xc, yc, r1, r2);
plotend();
return (0);
}
void plot_ul(const double x0, const double y0, const double width, const double height, const double r1, const double r2)
{
const double xc = x0 + (width / 2.0);
const double yc = y0 + (height / 2.0);
reuleaux(xc, yc, r2, 3, true);
reuleaux(xc, yc, r2 * 1.15, 3, false);
}
void plot_ur(const double x0, const double y0, const double width, const double height, const double r1, const double r2)
{
const double xc = x0 + (width / 2.0);
const double yc = y0 + (height / 2.0);
reuleaux(xc, yc, r2, 5, true);
reuleaux(xc, yc, r2 * 1.15, 5, false);
}
void plot_ll(const double x0, const double y0, const double width, const double height, const double r1, const double r2)
{
const double xc = x0 + (width / 2.0);
const double yc = y0 + (height / 2.0);
reuleaux(xc, yc, r2, 7, true);
reuleaux(xc, yc, r2 * 1.15, 7, false);
}
void plot_lr(const double x0, const double y0, const double width, const double height, const double r1, const double r2)
{
const double xc = x0 + (width / 2.0);
const double yc = y0 + (height / 2.0);
reuleaux(xc, yc, r2, 9, true);
reuleaux(xc, yc, r2 * 1.15, 9, false);
}
/* reuleaux --- draw a Reuleaux polygon centred on (xc, yc) */
void reuleaux(const double xc, const double yc, const double r, const int n, const bool drawSides)
{
/* https://en.wikipedia.org/wiki/Reuleaux_triangle */
int i;
const double delta = (2.0 * M_PI) / (double)n;
const double degrees = 180.0 / (double)n;
double x[32];
double y[32];
for (i = 0; i <= n; i++) {
const double theta = (delta * (double)i) + (M_PI / 2.0);
x[i] = xc + (r * cos(theta));
y[i] = yc + (r * sin(theta));
}
for (i = 0; i < n; i++) {
const int j = (i + (n / 2)) % n;
moveto(x[i], y[i]);
arc(x[j], y[j], -degrees);
}
if (drawSides) {
for (i = 0; i <= n; i++) {
if (i == 0)
moveto(x[i], y[i]);
else
lineto(x[i], y[i]);
}
}
}