1 /*
2 Produce spline (uniform knots, second order)
3 from guiding points
4 */
5 #include "mplot.h"
6 void splin(int mode, int num[], double *ff[]){
7 	int	i,  *np, n;
8 	double	xa, ya, xc, yc, *xp, *yp, *xp0, *yp0, *xpe, *ype;
9 	double **fp;
10 	np = num;
11 	fp = ff;
12 	while((n = *np++)){
13 		xp = *fp++; 
14 		yp = xp + 1; 
15 		xp0 = xp; 
16 		yp0 = yp;
17 		xpe = xp0 + 2 * (n - 1); 
18 		ype = yp0 + 2 * (n - 1);
19 		if (n < 3) { 
20 			plotline(*xp, *yp, *(xp + 2), *(yp + 2)); 
21 			continue;
22 		}
23 		if (mode == 4) {	/*closed curve*/
24 			xa = 0.5 * (*xpe + *(xpe - 2)); 
25 			xc = 0.5 * (*xpe + *xp0);
26 			ya = 0.5 * (*ype + *(ype - 2)); 
27 			yc = 0.5 * (*ype + *yp0);
28 			parabola(xa, ya, xc, yc, *xpe, *ype);
29 			xa = 0.5 * (*xpe + *xp0); 
30 			xc = 0.5 * (*(xp0 + 2) + *xp0);
31 			ya = 0.5 * (*ype + *yp0); 
32 			yc = 0.5 * (*(yp0 + 2) + *yp0);
33 			parabola(xa, ya, xc, yc, *xp0, *yp0);
34 		}
35 		else {	/*open curve with multiple endpoints*/
36 			if (mode % 2) /*odd mode makes first point double*/
37 				plotline(*xp0,*yp0,0.5*(*xp0+*(xp0+2)),0.5*(*yp0+*(yp0+2)));
38 		}
39 		xp += 2; 
40 		yp += 2;
41 		for (i = 1; i < (n - 1); i++, xp += 2, yp += 2) {
42 			xa = 0.5 * (*(xp - 2) + *xp); 
43 			xc = 0.5 * ( *xp + *(xp + 2));
44 			ya = 0.5 * (*(yp - 2) + *yp); 
45 			yc = 0.5 * ( *yp + *(yp + 2));
46 			parabola(xa, ya, xc, yc, *xp, *yp);
47 		}
48 		if(mode >= 2 && mode != 4)
49 			plotline(0.5*(*(xpe-2)+*xpe),0.5*(*(ype-2)+*ype),*xpe,*ype);
50 	}
51 }