--- ray/src/rt/virtuals.c	1991/06/25 13:11:53	1.9
+++ ray/src/rt/virtuals.c	1991/06/26 08:55:10	1.13
@@ -19,7 +19,10 @@ static char SCCSid[] = "$SunId$ LBL";
 
 #include  "random.h"
 
+#define  MINSAMPLES	3		/* minimum number of pretest samples */
+#define  STESTMAX	30		/* maximum seeks per sample */
 
+
 double  getdisk();
 
 static OBJECT  *vobject;		/* virtual source objects */
@@ -179,7 +182,7 @@ MAT4  pm;
 		}
 		if (source[sn].sflags & SFLAT) {	/* behind source? */
 			multv3(nsnorm, source[sn].snorm, pm);
-			if (checkspot(&ourspot, nsnorm) < 0)
+			if (!checkspot(&ourspot, nsnorm))
 				return(-1);
 		}
 	}
@@ -254,7 +257,7 @@ register int  sn;	/* target source number */
 	double  or, d;
 	int  infront;
 	int  ssn;
-	int  nhit;
+	int  nhit, nok;
 	register int  i, n;
 				/* return if pretesting disabled */
 	if (vspretest <= 0)
@@ -272,15 +275,15 @@ register int  sn;	/* target source number */
 		n = or2/DOT(offsdir,offsdir)*vspretest + .5;
 		infront = DOT(onorm, offsdir) > 0.;
 	}
-	if (n < 1) n = 1;
+	if (n < MINSAMPLES) n = MINSAMPLES;
 #ifdef DEBUG
 	fprintf(stderr, "pretesting source %d in object %s with %d rays\n",
 			sn, o->oname, n);
 #endif
 				/* sample */
 	or = sqrt(or2);
-	ssn = 25*n;
-	nhit = 0;
+	ssn = STESTMAX*n;
+	nhit = nok = 0;
 	while (n-- > 0) {
 					/* get sample point */
 		do {
@@ -316,16 +319,18 @@ register int  sn;	/* target source number */
 		rayvalue(&sr);
 		if (bright(sr.rcol) <= FTINY)
 			continue;
+		nok++;
 					/* check against obstructions */
 		srcray(&sr, NULL, sn);
 		rayvalue(&sr);
-		if (bright(sr.rcol) <= FTINY) {
+		if (bright(sr.rcol) > FTINY)
+			nhit++;
+		if (nhit > 0 && nhit < nok) {
 #ifdef DEBUG
-			fprintf(stderr, "\tfound an occlusion\n");
+			fprintf(stderr, "\tpartially occluded\n");
 #endif
-			return(f);	/* need to shadow test */
+			return(f);		/* need to shadow test */
 		}
-		nhit++;
 	}
 	if (nhit == 0) {
 #ifdef DEBUG