--- ray/src/common/dircode.c	2003/06/20 00:25:49	2.5
+++ ray/src/common/dircode.c	2019/08/27 23:51:23	2.10
@@ -1,13 +1,13 @@
 #ifndef lint
-static const char RCSid[] = "$Id: dircode.c,v 2.5 2003/06/20 00:25:49 greg Exp $";
+static const char RCSid[] = "$Id: dircode.c,v 2.10 2019/08/27 23:51:23 greg Exp $";
 #endif
 /*
- * Compute a 4-byte direction code (int32 type defined in standard.h).
+ * Compute a 4-byte direction code (externals defined in rtmath.h).
  *
  * Mean accuracy is 0.0022 degrees, with a maximum error of 0.0058 degrees.
  */
 
-#include "standard.h"
+#include "rtmath.h"
 
 #define	DCSCALE		11585.2		/* (1<<13)*sqrt(2) */
 #define FXNEG		01
@@ -20,12 +20,11 @@ static const char RCSid[] = "$Id: dircode.c,v 2.5 2003
 #define FMASK		0x1fff
 
 int32
-encodedir(dv)		/* encode a normalized direction vector */
-FVECT	dv;
+encodedir(FVECT dv)		/* encode a normalized direction vector */
 {
-	register int32	dc = 0;
+	int32	dc = 0;
 	int	cd[3], cm;
-	register int	i;
+	int	i;
 
 	for (i = 0; i < 3; i++)
 		if (dv[i] < 0.) {
@@ -33,6 +32,8 @@ FVECT	dv;
 			dc |= FXNEG<<i;
 		} else
 			cd[i] = (int)(dv[i] * DCSCALE);
+	if (!(cd[0] | cd[1] | cd[2]))
+		return(0);		/* zero normal */
 	if (cd[0] <= cd[1]) {
 		dc |= F1X | cd[0] << F1SFT;
 		cm = cd[1];
@@ -44,19 +45,22 @@ FVECT	dv;
 		dc |= F2Z | cd[2] << F2SFT;
 	else
 		dc |= cm << F2SFT;
-	if (!dc)	/* don't generate 0 code */
+	if (!dc)	/* don't generate 0 code normally */
 		dc = F1X;
 	return(dc);
 }
 
+#if 0		/* original version for reference */
 
 void
-decodedir(dv, dc)	/* decode a normalized direction vector */
-register FVECT	dv;	/* returned */
-register int32	dc;
+decodedir(FVECT dv, int32 dc)	/* decode a normalized direction vector */
 {
 	double	d1, d2, der;
 
+	if (!dc) {		/* special code for zero normal */
+		dv[0] = dv[1] = dv[2] = 0.;
+		return;
+	}
 	d1 = ((dc>>F1SFT & FMASK)+.5)*(1./DCSCALE);
 	d2 = ((dc>>F2SFT & FMASK)+.5)*(1./DCSCALE);
 	der = sqrt(1. - d1*d1 - d2*d2);
@@ -74,24 +78,51 @@ register int32	dc;
 	if (dc & FZNEG) dv[2] = -dv[2];
 }
 
+#else	
 
+void
+decodedir(FVECT dv, int32 dc)	/* decode a normalized direction vector */
+{
+	static const short	itab[4][3] = {
+					{1,0,2},{0,1,2},{1,2,0},{0,2,1}
+				};
+	static const RREAL	neg[2] = {1., -1.};
+	const int		ndx = ((dc & F2Z) != 0)<<1 | ((dc & F1X) != 0);
+	double			d1, d2, der;
+
+	if (!dc) {		/* special code for zero normal */
+		dv[0] = dv[1] = dv[2] = 0.;
+		return;
+	}
+	d1 = ((dc>>F1SFT & FMASK)+.5)*(1./DCSCALE);
+	d2 = ((dc>>F2SFT & FMASK)+.5)*(1./DCSCALE);
+	der = sqrt(1. - d1*d1 - d2*d2);
+	dv[itab[ndx][0]] = d1;
+	dv[itab[ndx][1]] = d2;
+	dv[itab[ndx][2]] = der;
+	dv[0] *= neg[(dc&FXNEG)!=0];
+	dv[1] *= neg[(dc&FYNEG)!=0];
+	dv[2] *= neg[(dc&FZNEG)!=0];
+}
+
+#endif
+
 double
-dir2diff(dc1, dc2)		/* approx. radians^2 between directions */
-int32	dc1, dc2;
+dir2diff(int32 dc1, int32 dc2)	/* approx. radians^2 between directions */
 {
 	FVECT	v1, v2;
 
+	if (dc1 == dc2)
+		return 0.;
+
 	decodedir(v1, dc1);
 	decodedir(v2, dc2);
 
 	return(2. - 2.*DOT(v1,v2));
 }
 
-
 double
-fdir2diff(dc1, v2)		/* approx. radians^2 between directions */
-int32	dc1;
-register FVECT	v2;
+fdir2diff(int32 dc1, FVECT v2)	/* approx. radians^2 between directions */
 {
 	FVECT	v1;