--- ray/src/rt/raytrace.c	1994/01/13 10:43:34	2.12
+++ ray/src/rt/raytrace.c	1995/01/26 15:34:55	2.19
@@ -1,4 +1,4 @@
-/* Copyright (c) 1994 Regents of the University of California */
+/* Copyright (c) 1995 Regents of the University of California */
 
 #ifndef lint
 static char SCCSid[] = "$SunId$ LBL";
@@ -34,6 +34,8 @@ OBJREC  Lamb = {
 	{0, 5, NULL, Lambfa}, NULL,
 };					/* a Lambertian surface */
 
+OBJREC  Aftplane;			/* aft clipping plane object */
+
 static int  raymove(), checkset(), checkhit();
 
 #define  MAXLOOP	128		/* modifier loop detection */
@@ -67,6 +69,7 @@ double  rw;
 		r->rweight = ro->rweight * rw;
 		r->crtype = ro->crtype | (r->rtype = rt);
 		VCOPY(r->rorg, ro->rop);
+		r->rmax = 0.0;
 	}
 	rayclear(r);
 	return(r->rlvl <= maxdepth && r->rweight >= minweight ? 0 : -1);
@@ -95,10 +98,13 @@ RAY  *r;
 
 	if (localhit(r, &thescene))
 		gotmat = raycont(r);
-	else if (sourcehit(r))
+	else if (r->ro == &Aftplane) {
+		r->ro = NULL;
+		r->rot = FHUGE;
+	} else if (sourcehit(r))
 		gotmat = rayshade(r, r->ro->omod);
 
-	if (!gotmat)
+	if (r->ro != NULL && !gotmat)
 		objerror(r->ro, USER, "material not found");
 
 	if (trace != NULL)
@@ -125,6 +131,8 @@ register RAY  *r;
 
 	if (rayorigin(&tr, r, TRANS, 1.0) == 0) {
 		VCOPY(tr.rdir, r->rdir);
+		if (r->rmax > FTINY)
+			tr.rmax = r->rmax - r->rot;
 		rayvalue(&tr);
 		copycolor(r->rcol, tr.rcol);
 		r->rt = r->rot + tr.rt;
@@ -156,7 +164,7 @@ int  mod;
 			if (irr_ignore(m->otype)) {
 				depth--;
 				raytrans(r);
-				return;
+				return(1);
 			}
 			if (!islight(m->otype))
 				m = &Lamb;
@@ -207,19 +215,24 @@ double  coef;
 		coef = 1.0;
 	else if (coef < 0.0)
 		coef = 0.0;
+					/* compute foreground and background */
+	foremat = backmat = -1;
 					/* foreground */
 	copystruct(&fr, r);
 	if (fore != OVOID && coef > FTINY)
 		foremat = rayshade(&fr, fore);
-	else
-		foremat = 0;
 					/* background */
 	copystruct(&br, r);
 	if (back != OVOID && coef < 1.0-FTINY)
 		backmat = rayshade(&br, back);
-	else
-		backmat = foremat;
 					/* check */
+	if (foremat < 0)
+		if (backmat < 0)
+			foremat = backmat = 0;
+		else
+			foremat = backmat;
+	else if (backmat < 0)
+		backmat = foremat;
 	if ((foremat==0) != (backmat==0))
 		objerror(r->ro, USER, "mixing material with non-material");
 					/* mix perturbations */
@@ -348,6 +361,14 @@ register CUBE  *scene;
 	}
 	if (sflags == 0)
 		error(CONSISTENCY, "zero ray direction in localhit");
+					/* start off assuming nothing hit */
+	if (r->rmax > FTINY) {		/* except aft plane if one */
+		r->ro = &Aftplane;
+		r->rot = r->rmax;
+		for (i = 0; i < 3; i++)
+			r->rop[i] = r->rorg[i] + r->rot*r->rdir[i];
+	}
+					/* find global cube entrance point */
 	t = 0.0;
 	if (!incube(scene, curpos)) {
 					/* find distance to entry */
@@ -365,6 +386,8 @@ register CUBE  *scene;
 				t = dt;	/* farthest face is the one */
 		}
 		t += FTINY;		/* fudge to get inside cube */
+		if (t >= r->rot)	/* clipped already */
+			return(0);
 					/* advance position */
 		for (i = 0; i < 3; i++)
 			curpos[i] += r->rdir[i]*t;
@@ -373,7 +396,8 @@ register CUBE  *scene;
 			return(0);
 	}
 	cxset[0] = 0;
-	return(raymove(curpos, cxset, sflags, r, scene) == RAYHIT);
+	raymove(curpos, cxset, sflags, r, scene);
+	return(r->ro != NULL & r->ro != &Aftplane);
 }
 
 
@@ -428,7 +452,10 @@ register CUBE  *cu;
 		}
 		/*NOTREACHED*/
 	}
-	if (isfull(cu->cutree) && checkhit(r, cu, cxs))
+	if (isfull(cu->cutree)) {
+		if (checkhit(r, cu, cxs))
+			return(RAYHIT);
+	} else if (r->ro == &Aftplane && incube(cu, r->rop))
 		return(RAYHIT);
 					/* advance to next cube */
 	if (dirf&0x11) {