--- ray/src/gen/mkillum2.c	1992/08/12 14:44:15	2.3
+++ ray/src/gen/mkillum2.c	1992/08/13 11:23:46	2.5
@@ -67,14 +67,16 @@ char  *nm;
 	if (distarr == NULL)
 		error(SYSTEM, "out of memory in o_face");
 				/* take first edge longer than sqrt(area) */
-	for (i = 1; i < fa->nv; i++) {
-		for (j = 0; j < 3; j++)
-			u[j] = VERTEX(fa,i)[j] - VERTEX(fa,i-1)[j];
-		if (DOT(u,u) >= fa->area-FTINY)
+	for (j = fa->nv-1, i = 0; i < fa->nv; j = i++) {
+		u[0] = VERTEX(fa,i)[0] - VERTEX(fa,j)[0];
+		u[1] = VERTEX(fa,i)[1] - VERTEX(fa,j)[1];
+		u[2] = VERTEX(fa,i)[2] - VERTEX(fa,j)[2];
+		if ((r1 = DOT(u,u)) >= fa->area-FTINY)
 			break;
 	}
 	if (i < fa->nv) {	/* got one! -- let's align our axes */
-		normalize(u);
+		r2 = 1.0/sqrt(r1);
+		u[0] *= r2; u[1] *= r2; u[2] *= r2;
 		fcross(v, fa->norm, u);
 	} else			/* oh well, we'll just have to wing it */
 		mkaxes(u, v, fa->norm);