--- ray/src/rt/sphere.c	1989/02/02 10:41:42	1.1
+++ ray/src/rt/sphere.c	1991/05/22 16:59:44	1.4
@@ -1,4 +1,4 @@
-/* Copyright (c) 1986 Regents of the University of California */
+/* Copyright (c) 1991 Regents of the University of California */
 
 #ifndef lint
 static char SCCSid[] = "$SunId$ LBL";
@@ -26,10 +26,16 @@ register RAY  *r;
 	register double  *ap;
 	register int  i;
 
-	if (so->oargs.nfargs != 4 || so->oargs.farg[3] <= FTINY)
-		objerror(so, USER, "bad arguments");
-
+	if (so->oargs.nfargs != 4)
+		objerror(so, USER, "bad # arguments");
 	ap = so->oargs.farg;
+	if (ap[3] < -FTINY) {
+		objerror(so, WARNING, "negative radius");
+		so->otype = so->otype == OBJ_SPHERE ?
+				OBJ_BUBBLE : OBJ_SPHERE;
+		ap[3] = -ap[3];
+	} else if (ap[3] <= FTINY)
+		objerror(so, USER, "zero radius");
 
 	/*
 	 *	We compute the intersection by substituting into
@@ -57,18 +63,21 @@ register RAY  *r;
 	if (i >= nroots)
 		return(0);			/* no positive root */
 
-	if (t < r->rot) {			/* found closer intersection */
-		r->ro = so;
-		r->rot = t;
-						/* compute normal */
-		a = ap[3];
-		if (so->otype == OBJ_BUBBLE)
-			a = -a;			/* reverse */
-		for (i = 0; i < 3; i++) {
-			r->rop[i] = r->rorg[i] + r->rdir[i]*t;
-			r->ron[i] = (r->rop[i] - ap[i]) / a;
-		}
-		r->rod = -DOT(r->rdir, r->ron);
+	if (t >= r->rot)
+		return(0);			/* other is closer */
+
+	r->ro = so;
+	r->rot = t;
+					/* compute normal */
+	a = ap[3];
+	if (so->otype == OBJ_BUBBLE)
+		a = -a;			/* reverse */
+	for (i = 0; i < 3; i++) {
+		r->rop[i] = r->rorg[i] + r->rdir[i]*t;
+		r->ron[i] = (r->rop[i] - ap[i]) / a;
 	}
-	return(1);
+	r->rod = -DOT(r->rdir, r->ron);
+	r->rox = NULL;
+
+	return(1);			/* hit */
 }