--- ray/src/rt/rtrace.c	1989/02/02 10:41:37	1.1
+++ ray/src/rt/rtrace.c	1990/01/04 11:16:05	1.7
@@ -16,6 +16,7 @@ static char SCCSid[] = "$SunId$ LBL";
  *	xorg	yorg	zorg	xdir	ydir	zdir
  *
  *  The direction need not be normalized.  Output is flexible.
+ *  If the direction vector is (0,0,0), then the output is flushed.
  *  All values default to ascii representation of real
  *  numbers.  Binary representations can be selected
  *  with '-ff' for float or '-fd' for double.  By default,
@@ -35,13 +36,15 @@ int  hresolu = 0;			/* horizontal (scan) size */
 int  vresolu = 0;			/* vertical resolution */
 
 double  dstrsrc = 0.0;			/* square source distribution */
+double  shadthresh = .05;		/* shadow threshold */
+double  shadcert = .5;			/* shadow certainty */
 
 int  maxdepth = 6;			/* maximum recursion depth */
 double  minweight = 4e-3;		/* minimum ray weight */
 
 COLOR  ambval = BLKCOLOR;		/* ambient value */
 double  ambacc = 0.2;			/* ambient accuracy */
-int  ambres = 128;			/* ambient resolution */
+int  ambres = 32;			/* ambient resolution */
 int  ambdiv = 128;			/* ambient divisions */
 int  ambssamp = 0;			/* ambient super-samples */
 int  ambounce = 0;			/* ambient bounces */
@@ -73,7 +76,7 @@ char  *fname;
 	long  vcount = hresolu>1 ? hresolu*vresolu : vresolu;
 	long  nextflush = hresolu;
 	FILE  *fp;
-	FVECT  orig, direc, vcol;
+	FVECT  orig, direc;
 					/* set up input */
 	if (fname == NULL)
 		fp = stdin;
@@ -92,14 +95,16 @@ char  *fname;
 	while (getvec(orig, inform, fp) == 0 &&
 			getvec(direc, inform, fp) == 0) {
 
-		if (normalize(direc) == 0.0)
-			error(USER, "zero direction vector");
+		if (normalize(direc) == 0.0) {		/* zero ==> flush */
+			fflush(stdout);
+			continue;
+		}
 							/* compute and print */
 		if (outvals[0] == 'i')
 			irrad(orig, direc);
 		else
 			radiance(orig, direc);
-							/* flush if requested */
+							/* flush if time */
 		if (--nextflush == 0) {
 			fflush(stdout);
 			nextflush = hresolu;