1 4314729d 2004-04-14 devnull #include "mplot.h"
 2 4314729d 2004-04-14 devnull /*		arc plotting routine		*/
 3 4314729d 2004-04-14 devnull /*		from x1,y1 to x2,y2		*/
 4 4314729d 2004-04-14 devnull /*	with center xc,yc and radius rr	*/
 5 4314729d 2004-04-14 devnull /*	integrates difference equation		*/
 6 4314729d 2004-04-14 devnull /*	negative rr draws counterclockwise	*/
 7 4314729d 2004-04-14 devnull #define PI4 0.7854
 8 4314729d 2004-04-14 devnull void rarc(double x1, double y1, double x2, double y2, double xc, double yc, double rr){
 9 4314729d 2004-04-14 devnull 	register double dx, dy, a, b;
10 4314729d 2004-04-14 devnull 	double	ph, dph, rd, xnext;
11 4314729d 2004-04-14 devnull 	register int	n;
12 4314729d 2004-04-14 devnull 	dx = x1 - xc;
13 4314729d 2004-04-14 devnull 	dy = y1 - yc;
14 4314729d 2004-04-14 devnull 	rd = sqrt(dx * dx + dy * dy);
15 4314729d 2004-04-14 devnull 	if (rd / e1->quantum < 1.0) { 
16 4314729d 2004-04-14 devnull 		move(xc, yc); 
17 4314729d 2004-04-14 devnull 		vec(xc, yc); 
18 4314729d 2004-04-14 devnull 		return;
19 4314729d 2004-04-14 devnull 	}
20 4314729d 2004-04-14 devnull 	dph = acos(1.0 - (e1->quantum / rd));
21 4314729d 2004-04-14 devnull 	if (dph > PI4) 
22 4314729d 2004-04-14 devnull 		dph = PI4;
23 4314729d 2004-04-14 devnull 	ph=atan2((y2-yc),(x2 - xc)) - atan2(dy, dx);
24 4314729d 2004-04-14 devnull 	if (ph < 0) 
25 4314729d 2004-04-14 devnull 		ph += 6.2832; 
26 4314729d 2004-04-14 devnull 	if (rr < 0) 
27 4314729d 2004-04-14 devnull 		ph = 6.2832 - ph;
28 4314729d 2004-04-14 devnull 	if (ph < dph) 
29 4314729d 2004-04-14 devnull 		plotline(x1, y1, x2, y2);
30 4314729d 2004-04-14 devnull 	else {
31 4314729d 2004-04-14 devnull 		n = ph / dph; 
32 4314729d 2004-04-14 devnull 		a = cos(dph); 
33 4314729d 2004-04-14 devnull 		b = sin(dph); 
34 4314729d 2004-04-14 devnull 		if (rr < 0) 
35 4314729d 2004-04-14 devnull 			b = -b;
36 4314729d 2004-04-14 devnull 		move(x1, y1);
37 4314729d 2004-04-14 devnull 		while ((n--) >= 0) {
38 4314729d 2004-04-14 devnull 			xnext = dx * a - dy * b; 
39 4314729d 2004-04-14 devnull 			dy = dx * b + dy * a; 
40 4314729d 2004-04-14 devnull 			dx = xnext;
41 4314729d 2004-04-14 devnull 			vec(dx + xc, dy + yc);
42 4314729d 2004-04-14 devnull 		}
43 4314729d 2004-04-14 devnull 	}
44 4314729d 2004-04-14 devnull }