--- ray/src/rt/normal.c	1992/05/15 13:07:55	2.18
+++ ray/src/rt/normal.c	1996/04/24 15:47:27	2.34
@@ -1,4 +1,4 @@
-/* Copyright (c) 1992 Regents of the University of California */
+/* Copyright (c) 1996 Regents of the University of California */
 
 #ifndef lint
 static char SCCSid[] = "$SunId$ LBL";
@@ -23,11 +23,17 @@ static char SCCSid[] = "$SunId$ LBL";
 extern double  specthresh;		/* specular sampling threshold */
 extern double  specjitter;		/* specular sampling jitter */
 
+extern int  backvis;			/* back faces visible? */
+
+#ifndef  MAXITER
+#define  MAXITER	10		/* maximum # specular ray attempts */
+#endif
+
+static  gaussamp();
+
 /*
- *	This routine uses portions of the reflection
- *  model described by Cook and Torrance.
- *	The computation of specular components has been simplified by
- *  numerous approximations and ommisions to improve speed.
+ *	This routine implements the isotropic Gaussian
+ *  model described by Ward in Siggraph `92 article.
  *	We orient the surface towards the incoming ray, so a single
  *  surface can be used to represent an infinitely thin object.
  *
@@ -38,8 +44,6 @@ extern double  specjitter;		/* specular sampling jitte
  *	red 	grn	blu	rspec	rough	trans	tspec
  */
 
-#define  BSPEC(m)	(6.0)		/* specularity parameter b */
-
 				/* specularity flags */
 #define  SP_REFL	01		/* has reflected specular component */
 #define  SP_TRAN	02		/* has transmitted specular */
@@ -104,12 +108,13 @@ double  omega;			/* light source size */
 						/* + source if flat */
 		if (np->specfl & SP_FLAT)
 			dtmp += omega/(4.0*PI);
-						/* delta */
+						/* half vector */
 		vtmp[0] = ldir[0] - np->rp->rdir[0];
 		vtmp[1] = ldir[1] - np->rp->rdir[1];
 		vtmp[2] = ldir[2] - np->rp->rdir[2];
 		d2 = DOT(vtmp, np->pnorm);
-		d2 = 2.0 - 2.0*d2/sqrt(DOT(vtmp,vtmp));
+		d2 *= d2;
+		d2 = (DOT(vtmp,vtmp) - d2) / d2;
 						/* gaussian */
 		dtmp = exp(-d2/dtmp)/(4.*PI*dtmp);
 						/* worth using? */
@@ -135,9 +140,9 @@ double  omega;			/* light source size */
 		 *  is always modified by material color.
 		 */
 						/* roughness + source */
-		dtmp = np->alpha2/4.0 + omega/PI;
+		dtmp = np->alpha2 + omega/PI;
 						/* gaussian */
-		dtmp = exp((2.*DOT(np->prdir,ldir)-2.)/dtmp)/(4.*PI*dtmp);
+		dtmp = exp((2.*DOT(np->prdir,ldir)-2.)/dtmp)/(PI*dtmp);
 						/* worth using? */
 		if (dtmp > FTINY) {
 			copycolor(ctmp, np->mcolor);
@@ -155,15 +160,25 @@ register RAY  *r;
 {
 	NORMDAT  nd;
 	double  transtest, transdist;
-	double  dtmp;
+	double	mirtest, mirdist;
+	int	hastexture;
+	double	d;
 	COLOR  ctmp;
 	register int  i;
 						/* easy shadow test */
 	if (r->crtype & SHADOW && m->otype != MAT_TRANS)
-		return;
+		return(1);
 
 	if (m->oargs.nfargs != (m->otype == MAT_TRANS ? 7 : 5))
 		objerror(m, USER, "bad number of arguments");
+						/* check for back side */
+	if (r->rod < 0.0) {
+		if (!backvis && m->otype != MAT_TRANS) {
+			raytrans(r);
+			return(1);
+		}
+		flipsurface(r);			/* reorient if backvis */
+	}
 	nd.mp = m;
 	nd.rp = r;
 						/* get material color */
@@ -175,53 +190,22 @@ register RAY  *r;
 	nd.alpha2 = m->oargs.farg[4];
 	if ((nd.alpha2 *= nd.alpha2) <= FTINY)
 		nd.specfl |= SP_PURE;
-						/* reorient if necessary */
-	if (r->rod < 0.0)
-		flipsurface(r);
+	if (r->ro != NULL && isflat(r->ro->otype))
+		nd.specfl |= SP_FLAT;
 						/* get modifiers */
 	raytexture(r, m->omod);
-	nd.pdot = raynormal(nd.pnorm, r);	/* perturb normal */
+	if (hastexture = DOT(r->pert,r->pert) > FTINY*FTINY)
+		nd.pdot = raynormal(nd.pnorm, r);	/* perturb normal */
+	else {
+		VCOPY(nd.pnorm, r->ron);
+		nd.pdot = r->rod;
+	}
 	if (nd.pdot < .001)
 		nd.pdot = .001;			/* non-zero for dirnorm() */
 	multcolor(nd.mcolor, r->pcol);		/* modify material color */
-	transtest = 0;
-						/* get specular component */
-	if ((nd.rspec = m->oargs.farg[3]) > FTINY) {
-		nd.specfl |= SP_REFL;
-						/* compute specular color */
-		if (m->otype == MAT_METAL)
-			copycolor(nd.scolor, nd.mcolor);
-		else
-			setcolor(nd.scolor, 1.0, 1.0, 1.0);
-		scalecolor(nd.scolor, nd.rspec);
-						/* improved model */
-		dtmp = exp(-BSPEC(m)*nd.pdot);
-		for (i = 0; i < 3; i++)
-			colval(nd.scolor,i) += (1.0-colval(nd.scolor,i))*dtmp;
-		nd.rspec += (1.0-nd.rspec)*dtmp;
-						/* check threshold */
-		if (!(nd.specfl & SP_PURE) &&
-				specthresh > FTINY &&
-				(specthresh >= 1.-FTINY ||
-				specthresh + .05 - .1*frandom() > nd.rspec))
-			nd.specfl |= SP_RBLT;
-						/* compute reflected ray */
-		for (i = 0; i < 3; i++)
-			nd.vrefl[i] = r->rdir[i] + 2.0*nd.pdot*nd.pnorm[i];
-		if (DOT(nd.vrefl, r->ron) <= FTINY)	/* penetration? */
-			for (i = 0; i < 3; i++)		/* safety measure */
-				nd.vrefl[i] = r->rdir[i] + 2.*r->rod*r->ron[i];
-
-		if (!(r->crtype & SHADOW) && nd.specfl & SP_PURE) {
-			RAY  lr;
-			if (rayorigin(&lr, r, REFLECTED, nd.rspec) == 0) {
-				VCOPY(lr.rdir, nd.vrefl);
-				rayvalue(&lr);
-				multcolor(lr.rcol, nd.scolor);
-				addcolor(r->rcol, lr.rcol);
-			}
-		}
-	}
+	mirtest = transtest = 0;
+	mirdist = transdist = r->rot;
+	nd.rspec = m->oargs.farg[3];
 						/* compute transmission */
 	if (m->otype == MAT_TRANS) {
 		nd.trans = m->oargs.farg[5]*(1.0 - nd.rspec);
@@ -230,18 +214,15 @@ register RAY  *r;
 		if (nd.tspec > FTINY) {
 			nd.specfl |= SP_TRAN;
 							/* check threshold */
-			if (!(nd.specfl & SP_PURE) && specthresh > FTINY &&
-					(specthresh >= 1.-FTINY ||
-				specthresh + .05 - .1*frandom() > nd.tspec))
+			if (!(nd.specfl & SP_PURE) &&
+					specthresh >= nd.tspec-FTINY)
 				nd.specfl |= SP_TBLT;
-			if (r->crtype & SHADOW ||
-					DOT(r->pert,r->pert) <= FTINY*FTINY) {
+			if (!hastexture || r->crtype & SHADOW) {
 				VCOPY(nd.prdir, r->rdir);
 				transtest = 2;
 			} else {
 				for (i = 0; i < 3; i++)		/* perturb */
-					nd.prdir[i] = r->rdir[i] -
-							0.5*r->pert[i];
+					nd.prdir[i] = r->rdir[i] - r->pert[i];
 				if (DOT(nd.prdir, r->ron) < -FTINY)
 					normalize(nd.prdir);	/* OK */
 				else
@@ -251,7 +232,7 @@ register RAY  *r;
 	} else
 		nd.tdiff = nd.tspec = nd.trans = 0.0;
 						/* transmitted ray */
-	if ((nd.specfl&(SP_TRAN|SP_PURE)) == (SP_TRAN|SP_PURE)) {
+	if (nd.specfl&SP_TRAN && (nd.specfl&SP_PURE || r->crtype&SHADOW)) {
 		RAY  lr;
 		if (rayorigin(&lr, r, TRANS, nd.tspec) == 0) {
 			VCOPY(lr.rdir, nd.prdir);
@@ -265,23 +246,55 @@ register RAY  *r;
 	} else
 		transtest = 0;
 
-	if (r->crtype & SHADOW)			/* the rest is shadow */
-		return;
+	if (r->crtype & SHADOW) {		/* the rest is shadow */
+		r->rt = transdist;
+		return(1);
+	}
+						/* get specular reflection */
+	if (nd.rspec > FTINY) {
+		nd.specfl |= SP_REFL;
+						/* compute specular color */
+		if (m->otype == MAT_METAL)
+			copycolor(nd.scolor, nd.mcolor);
+		else
+			setcolor(nd.scolor, 1.0, 1.0, 1.0);
+		scalecolor(nd.scolor, nd.rspec);
+						/* check threshold */
+		if (!(nd.specfl & SP_PURE) && specthresh >= nd.rspec-FTINY)
+			nd.specfl |= SP_RBLT;
+						/* compute reflected ray */
+		for (i = 0; i < 3; i++)
+			nd.vrefl[i] = r->rdir[i] + 2.*nd.pdot*nd.pnorm[i];
+						/* penetration? */
+		if (hastexture && DOT(nd.vrefl, r->ron) <= FTINY)
+			for (i = 0; i < 3; i++)		/* safety measure */
+				nd.vrefl[i] = r->rdir[i] + 2.*r->rod*r->ron[i];
+
+		if (!(r->crtype & SHADOW) && nd.specfl & SP_PURE) {
+			RAY  lr;
+			if (rayorigin(&lr, r, REFLECTED, nd.rspec) == 0) {
+				VCOPY(lr.rdir, nd.vrefl);
+				rayvalue(&lr);
+				multcolor(lr.rcol, nd.scolor);
+				addcolor(r->rcol, lr.rcol);
+				if (!hastexture && nd.specfl & SP_FLAT) {
+					mirtest = 2.*bright(lr.rcol);
+					mirdist = r->rot + lr.rt;
+				}
+			}
+		}
+	}
 						/* diffuse reflection */
 	nd.rdiff = 1.0 - nd.trans - nd.rspec;
 
 	if (nd.specfl & SP_PURE && nd.rdiff <= FTINY && nd.tdiff <= FTINY)
-		return;				/* 100% pure specular */
+		return(1);			/* 100% pure specular */
 
-	if (r->ro != NULL && (r->ro->otype == OBJ_FACE ||
-			r->ro->otype == OBJ_RING))
-		nd.specfl |= SP_FLAT;
-
 	if (nd.specfl & (SP_REFL|SP_TRAN) && !(nd.specfl & SP_PURE))
 		gaussamp(r, &nd);
 
 	if (nd.rdiff > FTINY) {		/* ambient from this side */
-		ambient(ctmp, r);
+		ambient(ctmp, r, hastexture?nd.pnorm:r->ron);
 		if (nd.specfl & SP_RBLT)
 			scalecolor(ctmp, 1.0-nd.trans);
 		else
@@ -291,7 +304,14 @@ register RAY  *r;
 	}
 	if (nd.tdiff > FTINY) {		/* ambient from other side */
 		flipsurface(r);
-		ambient(ctmp, r);
+		if (hastexture) {
+			FVECT  bnorm;
+			bnorm[0] = -nd.pnorm[0];
+			bnorm[1] = -nd.pnorm[1];
+			bnorm[2] = -nd.pnorm[2];
+			ambient(ctmp, r, bnorm);
+		} else
+			ambient(ctmp, r, r->ron);
 		if (nd.specfl & SP_TBLT)
 			scalecolor(ctmp, nd.trans);
 		else
@@ -303,8 +323,13 @@ register RAY  *r;
 					/* add direct component */
 	direct(r, dirnorm, &nd);
 					/* check distance */
-	if (transtest > bright(r->rcol))
+	d = bright(r->rcol);
+	if (transtest > d)
 		r->rt = transdist;
+	else if (mirtest > d)
+		r->rt = mirdist;
+
+	return(1);
 }
 
 
@@ -317,6 +342,7 @@ register NORMDAT  *np;
 	FVECT  u, v, h;
 	double  rv[2];
 	double  d, sinp, cosp;
+	int  niter;
 	register int  i;
 					/* quick test */
 	if ((np->specfl & (SP_REFL|SP_RBLT)) != SP_REFL &&
@@ -335,52 +361,63 @@ register NORMDAT  *np;
 	if ((np->specfl & (SP_REFL|SP_RBLT)) == SP_REFL &&
 			rayorigin(&sr, r, SPECULAR, np->rspec) == 0) {
 		dimlist[ndims++] = (int)np->mp;
-		d = urand(ilhash(dimlist,ndims)+samplendx);
-		multisamp(rv, 2, d);
-		d = 2.0*PI * rv[0];
-		cosp = cos(d);
-		sinp = sin(d);
-		rv[1] = 1.0 - specjitter*rv[1];
-		if (rv[1] <= FTINY)
-			d = 1.0;
-		else
-			d = sqrt( np->alpha2 * -log(rv[1]) );
-		for (i = 0; i < 3; i++)
-			h[i] = np->pnorm[i] + d*(cosp*u[i] + sinp*v[i]);
-		d = -2.0 * DOT(h, r->rdir) / (1.0 + d*d);
-		for (i = 0; i < 3; i++)
-			sr.rdir[i] = r->rdir[i] + d*h[i];
-		if (DOT(sr.rdir, r->ron) <= FTINY)
-			VCOPY(sr.rdir, np->vrefl);	/* jitter no good */
-		rayvalue(&sr);
-		multcolor(sr.rcol, np->scolor);
-		addcolor(r->rcol, sr.rcol);
+		for (niter = 0; niter < MAXITER; niter++) {
+			if (niter)
+				d = frandom();
+			else
+				d = urand(ilhash(dimlist,ndims)+samplendx);
+			multisamp(rv, 2, d);
+			d = 2.0*PI * rv[0];
+			cosp = cos(d);
+			sinp = sin(d);
+			rv[1] = 1.0 - specjitter*rv[1];
+			if (rv[1] <= FTINY)
+				d = 1.0;
+			else
+				d = sqrt( np->alpha2 * -log(rv[1]) );
+			for (i = 0; i < 3; i++)
+				h[i] = np->pnorm[i] + d*(cosp*u[i] + sinp*v[i]);
+			d = -2.0 * DOT(h, r->rdir) / (1.0 + d*d);
+			for (i = 0; i < 3; i++)
+				sr.rdir[i] = r->rdir[i] + d*h[i];
+			if (DOT(sr.rdir, r->ron) > FTINY) {
+				rayvalue(&sr);
+				multcolor(sr.rcol, np->scolor);
+				addcolor(r->rcol, sr.rcol);
+				break;
+			}
+		}
 		ndims--;
 	}
 					/* compute transmission */
 	if ((np->specfl & (SP_TRAN|SP_TBLT)) == SP_TRAN &&
 			rayorigin(&sr, r, SPECULAR, np->tspec) == 0) {
 		dimlist[ndims++] = (int)np->mp;
-		d = urand(ilhash(dimlist,ndims)+1823+samplendx);
-		multisamp(rv, 2, d);
-		d = 2.0*PI * rv[0];
-		cosp = cos(d);
-		sinp = sin(d);
-		rv[1] = 1.0 - specjitter*rv[1];
-		if (rv[1] <= FTINY)
-			d = 1.0;
-		else
-			d = sqrt( np->alpha2/4.0 * -log(rv[1]) );
-		for (i = 0; i < 3; i++)
-			sr.rdir[i] = np->prdir[i] + d*(cosp*u[i] + sinp*v[i]);
-		if (DOT(sr.rdir, r->ron) < -FTINY)
-			normalize(sr.rdir);		/* OK, normalize */
-		else
-			VCOPY(sr.rdir, np->prdir);	/* else no jitter */
-		rayvalue(&sr);
-		scalecolor(sr.rcol, np->tspec);
-		multcolor(sr.rcol, np->mcolor);		/* modified by color */
-		addcolor(r->rcol, sr.rcol);
+		for (niter = 0; niter < MAXITER; niter++) {
+			if (niter)
+				d = frandom();
+			else
+				d = urand(ilhash(dimlist,ndims)+1823+samplendx);
+			multisamp(rv, 2, d);
+			d = 2.0*PI * rv[0];
+			cosp = cos(d);
+			sinp = sin(d);
+			rv[1] = 1.0 - specjitter*rv[1];
+			if (rv[1] <= FTINY)
+				d = 1.0;
+			else
+				d = sqrt( -log(rv[1]) * np->alpha2 );
+			for (i = 0; i < 3; i++)
+				sr.rdir[i] = np->prdir[i] + d*(cosp*u[i] + sinp*v[i]);
+			if (DOT(sr.rdir, r->ron) < -FTINY) {
+				normalize(sr.rdir);	/* OK, normalize */
+				rayvalue(&sr);
+				scalecolor(sr.rcol, np->tspec);
+				multcolor(sr.rcol, np->mcolor);	/* modified */
+				addcolor(r->rcol, sr.rcol);
+				break;
+			}
+		}
 		ndims--;
 	}
 }