1 files changed, 51 insertions, 0 deletions
diff --git a/src/cmd/plot/libplot/spline.c b/src/cmd/plot/libplot/spline.c
new file mode 100644
index 00000000..8cfa83d7
--- /dev/null
+++ b/src/cmd/plot/libplot/spline.c
@@ -0,0 +1,51 @@
+/*
+Produce spline (uniform knots, second order)
+from guiding points
+*/
+#include "mplot.h"
+void splin(int mode, int num[], double *ff[]){
+	int	i,  *np, n;
+	double	xa, ya, xc, yc, *xp, *yp, *xp0, *yp0, *xpe, *ype;
+	double **fp;
+	np = num;
+	fp = ff;
+	while((n = *np++)){
+		xp = *fp++; 
+		yp = xp + 1; 
+		xp0 = xp; 
+		yp0 = yp;
+		xpe = xp0 + 2 * (n - 1); 
+		ype = yp0 + 2 * (n - 1);
+		if (n < 3) { 
+			plotline(*xp, *yp, *(xp + 2), *(yp + 2)); 
+			continue;
+		}
+		if (mode == 4) {	/*closed curve*/
+			xa = 0.5 * (*xpe + *(xpe - 2)); 
+			xc = 0.5 * (*xpe + *xp0);
+			ya = 0.5 * (*ype + *(ype - 2)); 
+			yc = 0.5 * (*ype + *yp0);
+			parabola(xa, ya, xc, yc, *xpe, *ype);
+			xa = 0.5 * (*xpe + *xp0); 
+			xc = 0.5 * (*(xp0 + 2) + *xp0);
+			ya = 0.5 * (*ype + *yp0); 
+			yc = 0.5 * (*(yp0 + 2) + *yp0);
+			parabola(xa, ya, xc, yc, *xp0, *yp0);
+		}
+		else {	/*open curve with multiple endpoints*/
+			if (mode % 2) /*odd mode makes first point double*/
+				plotline(*xp0,*yp0,0.5*(*xp0+*(xp0+2)),0.5*(*yp0+*(yp0+2)));
+		}
+		xp += 2; 
+		yp += 2;
+		for (i = 1; i < (n - 1); i++, xp += 2, yp += 2) {
+			xa = 0.5 * (*(xp - 2) + *xp); 
+			xc = 0.5 * ( *xp + *(xp + 2));
+			ya = 0.5 * (*(yp - 2) + *yp); 
+			yc = 0.5 * ( *yp + *(yp + 2));
+			parabola(xa, ya, xc, yc, *xp, *yp);
+		}
+		if(mode >= 2 && mode != 4)
+			plotline(0.5*(*(xpe-2)+*xpe),0.5*(*(ype-2)+*ype),*xpe,*ype);
+	}
+}