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195 lines (157 loc) · 4.7 KB
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/* pconic --- plot Bezier curves */
/* Note: this program was originally written for a non-HPGL plotter,
the BMC B-1000. It uses a slightly different command language from HPGL,
although the commands are still two ASCII letters.
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <math.h>
#include "hpgllib.h"
#define NPTS (16)
struct Weights {
double w0;
double w1;
double w2;
};
struct Point {
double x, y;
};
double quadfunc(const struct Weights *const wp, const double x0, const double x1, const double x2,
const double u);
void genconic(struct Point p0, struct Point p1, struct Point p2, const struct Weights *const wt, double x[], double y[], double w[], const int n);
void gencurve(const struct Weights *const wp, const double x0, const double x1, const double x2,
double x[], const int n);
void showcurve(const int colr, double xpts[], double ypts[], double wpts[], const int n);
int main(const int argc, char *const argv[])
{
int opt;
double maxx, maxy;
static struct Point p0 = {
180.0 * 40.0, 250.0 * 40.0
};
static struct Point p1 = {
0.0, 250.0 * 40.0
};
static struct Point p2 = {
0.0, 125.0 * 40.0
};
static struct Point p3 = {
0.0, 0.0
};
static struct Point p4 = {
180.0 * 40.0, 0.0
};
static struct Point p5 = {
360.0 * 40.0, 0.0
};
static struct Point p6 = {
360.0 * 40.0, 125.0 * 40.0
};
static struct Point p7 = {
360.0 * 40.0, 250.0 * 40.0
};
double xpts[NPTS + 1], ypts[NPTS + 1], wpts[NPTS + 1];
struct Weights wt;
int i;
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);
}
// printf ("IP1;PS3;\n");
getplotsize(&maxx, &maxy);
wt.w0 = 1.0;
wt.w1 = 3.0;
wt.w2 = 1.0;
for (i = 0; i < 10; i++) {
p1.x = (8.0 * 40.0) * i;
p2.x = p1.x;
p3.x = p1.x;
p5.x = (360.0 * 40.0) - ((8.0 * 40.0) * i);
p6.x = p5.x;
p7.x = p5.x;
p0.y = (250.0 * 40.0) - ((8.0 * 40.0) * i);
p1.y = p0.y;
p7.y = p0.y;
genconic(p0, p1, p2, &wt, xpts, ypts, wpts, NPTS);
showcurve(1, xpts, ypts, wpts, NPTS);
genconic(p2, p3, p4, &wt, xpts, ypts, wpts, NPTS);
showcurve(1, xpts, ypts, wpts, NPTS);
genconic(p4, p5, p6, &wt, xpts, ypts, wpts, NPTS);
showcurve(1, xpts, ypts, wpts, NPTS);
genconic(p6, p7, p0, &wt, xpts, ypts, wpts, NPTS);
showcurve(1, xpts, ypts, wpts, NPTS);
}
// printf("MA0,0;CH\n");
plotend();
return (0);
}
/* quadfunc --- rational quadratic function */
double quadfunc(const struct Weights *const wp, const double x0, const double x1, const double x2,
const double u)
{
double t0, t1, t2;
t0 = 1.0 - u;
t0 *= t0;
t0 *= x0 * wp->w0;
t1 = u * (1.0 - u);
t1 *= 2.0;
t1 *= x1 * wp->w1;
t2 = u * u;
t2 *= x2 * wp->w2;
return (t0 + t1 + t2);
}
/* gencurve --- generate 'n + 1' points on the curve */
void gencurve(const struct Weights *const wp, const double x0, const double x1, const double x2,
double x[], const int n)
{
const double step = 1.0 / (double)n; /* The increment in 't' for each step */
int i;
for (i = 0; i <= n; i++) {
const double t = i * step; /* The parameter, 0..1 */
x[i] = quadfunc(wp, x0, x1, x2, t);
}
}
/* genconic --- generate a conic section from 'p0' to 'p2' */
void genconic(struct Point p0, struct Point p1, struct Point p2, const struct Weights *const wt, double x[], double y[], double w[], const int n)
{
gencurve(wt, p0.x, p1.x, p2.x, x, n);
gencurve(wt, p0.y, p1.y, p2.y, y, n);
gencurve(wt, 1.0, 1.0, 1.0, w, n);
}
void showcurve(const int colr, double xpts[], double ypts[], double wpts[], const int n)
{
int i;
int x, y;
x = (xpts[0] / wpts[0]) + 0.5;
y = (ypts[0] / wpts[0]) + 0.5;
// printf("MA%d,%d\n", y, x);
moveto(x, y);
// printf("DA");
for (i = 1; i <= n; i++) {
x = (xpts[i] / wpts[i]) + 0.5;
y = (ypts[i] / wpts[i]) + 0.5;
// printf("%05d,%05d", x, y);
// if (i < n)
// printf(",");
lineto(x, y);
}
// printf("\n");
}