--- ray/src/common/face.c	2003/03/14 21:27:45	2.9
+++ ray/src/common/face.c	2016/09/16 15:09:21	2.13
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: face.c,v 2.9 2003/03/14 21:27:45 greg Exp $";
+static const char RCSid[] = "$Id: face.c,v 2.13 2016/09/16 15:09:21 greg Exp $";
 #endif
 /*
  *  face.c - routines dealing with polygonal faces.
@@ -32,14 +32,15 @@ static const char RCSid[] = "$Id: face.c,v 2.9 2003/03
 
 
 FACE *
-getface(o)			/* get arguments for a face */
-OBJREC  *o;
+getface(				/* get arguments for a face */
+	OBJREC  *o
+)
 {
 	double  d1;
-	int  badvert;
+	int  smalloff, badvert;
 	FVECT  v1, v2, v3;
-	register FACE  *f;
-	register int  i;
+	FACE  *f;
+	int  i;
 
 	if ((f = (FACE *)o->os) != NULL)
 		return(f);			/* already done */
@@ -84,9 +85,13 @@ OBJREC  *o;
 						/* compute offset */
 	badvert = 0;
 	f->offset = DOT(f->norm, VERTEX(f,0));
+	smalloff = fabs(f->offset) <= VERTEPS;
 	for (i = 1; i < f->nv; i++) {
 		d1 = DOT(f->norm, VERTEX(f,i));
-		badvert += fabs(1.0 - d1*i/f->offset) > VERTEPS;
+		if (smalloff)
+			badvert += fabs(d1 - f->offset/i) > VERTEPS;
+		else
+			badvert += fabs(1.0 - d1*i/f->offset) > VERTEPS;
 		f->offset += d1;
 	}
 	f->offset /= (double)f->nv;
@@ -102,8 +107,9 @@ OBJREC  *o;
 
 
 void
-freeface(o)			/* free memory associated with face */
-OBJREC  *o;
+freeface(			/* free memory associated with face */
+	OBJREC  *o
+)
 {
 	if (o->os == NULL)
 		return;
@@ -113,18 +119,19 @@ OBJREC  *o;
 
 
 int
-inface(p, f)			/* determine if point is in face */
-FVECT  p;
-FACE  *f;
+inface(				/* determine if point is in face */
+	FVECT  p,
+	FACE  *f
+)
 {
 	int  ncross, n;
 	double  x, y;
 	int  tst;
-	register int  xi, yi;
-	register FLOAT  *p0, *p1;
+	int  xi, yi;
+	RREAL  *p0, *p1;
 
-	xi = (f->ax+1)%3;
-	yi = (f->ax+2)%3;
+	if ((xi = f->ax + 1) >= 3) xi -= 3;
+	if ((yi = xi + 1) >= 3) yi -= 3;
 	x = p[xi];
 	y = p[yi];
 	n = f->nv;