--- ray/src/common/fvect.c	2013/06/29 21:03:44	2.19
+++ ray/src/common/fvect.c	2015/05/21 05:54:54	2.22
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: fvect.c,v 2.19 2013/06/29 21:03:44 greg Exp $";
+static const char	RCSid[] = "$Id: fvect.c,v 2.22 2015/05/21 05:54:54 greg Exp $";
 #endif
 /*
  *  fvect.c - routines for floating-point vector calculations
@@ -10,6 +10,7 @@ static const char	RCSid[] = "$Id: fvect.c,v 2.19 2013/
 #define _USE_MATH_DEFINES
 #include  <math.h>
 #include  "fvect.h"
+#include  "random.h"
 
 double
 Acos(double x)			/* insurance for touchy math library */
@@ -105,6 +106,12 @@ const FVECT v1,
 const FVECT v2
 )
 {
+	if ((vres == v1) | (vres == v2)) {
+		FVECT	vtmp;
+		VCROSS(vtmp, v1, v2);
+		VCOPY(vres, vtmp);
+		return;
+	}
 	VCROSS(vres, v1, v2);
 }
 
@@ -145,6 +152,53 @@ FVECT  v
 	v[2] *= d;
 
 	return(len);
+}
+
+
+int
+getperpendicular(		/* choose perpedicular direction */
+FVECT vp,				/* returns normalized */
+const FVECT v,				/* input vector must be normalized */
+int randomize				/* randomize orientation */
+)
+{
+	int	ord[3];
+	FVECT	v1;
+	int	i;
+
+	if (randomize) {		/* randomize coordinates? */
+		v1[0] = 0.5 - frandom();
+		v1[1] = 0.5 - frandom();
+		v1[2] = 0.5 - frandom();
+		switch (ord[0] = (int)(frandom()*2.99999)) {
+		case 0:
+			ord[1] = 1 + (frandom() > .5);
+			ord[2] = 2 - ord[1];
+			break;
+		case 1:
+			ord[1] = 2*(frandom() > .5);
+			ord[2] = 2 - ord[1];
+			break;
+		case 2:
+			ord[1] = (frandom() > .5);
+			ord[2] = 1 - ord[1];
+			break;
+		}
+	} else {
+		v1[0] = v1[1] = v1[2] = .0;
+		ord[0] = 0; ord[1] = 1; ord[2] = 2;
+	}
+
+	for (i = 3; i--; )
+		if ((-0.6 < v[ord[i]]) & (v[ord[i]] < 0.6))
+			break;
+	if (i < 0)
+		return(0);
+
+	v1[ord[i]] = 1.0;
+	fcross(vp, v1, v);
+
+	return(normalize(vp) > 0.0);
 }