--- ray/src/rt/normal.c	1992/02/21 14:53:16	2.11
+++ ray/src/rt/normal.c	1995/11/22 09:27:55	2.32
@@ -1,4 +1,4 @@
-/* Copyright (c) 1992 Regents of the University of California */
+/* Copyright (c) 1995 Regents of the University of California */
 
 #ifndef lint
 static char SCCSid[] = "$SunId$ LBL";
@@ -23,11 +23,13 @@ static char SCCSid[] = "$SunId$ LBL";
 extern double  specthresh;		/* specular sampling threshold */
 extern double  specjitter;		/* specular sampling jitter */
 
+extern int  backvis;			/* back faces visible? */
+
+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 +40,6 @@ 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 */
@@ -50,6 +50,7 @@ extern double  specjitter;		/* specular sampling jitte
 
 typedef struct {
 	OBJREC  *mp;		/* material pointer */
+	RAY  *rp;		/* ray pointer */
 	short  specfl;		/* specularity flags, defined above */
 	COLOR  mcolor;		/* color of this material */
 	COLOR  scolor;		/* color of specular component */
@@ -71,8 +72,8 @@ FVECT  ldir;			/* light source direction */
 double  omega;			/* light source size */
 {
 	double  ldot;
-	double  dtmp;
-	int	i;
+	double  dtmp, d2;
+	FVECT  vtmp;
 	COLOR  ctmp;
 
 	setcolor(cval, 0.0, 0.0, 0.0);
@@ -99,16 +100,23 @@ double  omega;			/* light source size */
 		 *  gaussian distribution model.
 		 */
 						/* roughness */
-		dtmp = 2.0*np->alpha2;
+		dtmp = np->alpha2;
 						/* + source if flat */
 		if (np->specfl & SP_FLAT)
-			dtmp += omega/(2.0*PI);
+			dtmp += omega/(4.0*PI);
+						/* 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 *= d2;
+		d2 = (DOT(vtmp,vtmp) - d2) / d2;
 						/* gaussian */
-		dtmp = exp((DOT(np->vrefl,ldir)-1.)/dtmp)/(2.*PI)/dtmp;
+		dtmp = exp(-d2/dtmp)/(4.*PI*dtmp);
 						/* worth using? */
 		if (dtmp > FTINY) {
 			copycolor(ctmp, np->scolor);
-			dtmp *= omega / np->pdot;
+			dtmp *= omega * sqrt(ldot/np->pdot);
 			scalecolor(ctmp, dtmp);
 			addcolor(cval, ctmp);
 		}
@@ -128,13 +136,13 @@ double  omega;			/* light source size */
 		 *  is always modified by material color.
 		 */
 						/* roughness + source */
-		dtmp = np->alpha2/2.0 + omega/(2.0*PI);
+		dtmp = np->alpha2 + omega/PI;
 						/* gaussian */
-		dtmp = exp((DOT(np->prdir,ldir)-1.)/dtmp)/(2.*PI)/dtmp;
+		dtmp = exp((2.*DOT(np->prdir,ldir)-2.)/dtmp)/(PI*dtmp);
 						/* worth using? */
 		if (dtmp > FTINY) {
 			copycolor(ctmp, np->mcolor);
-			dtmp *= np->tspec * omega / np->pdot;
+			dtmp *= np->tspec * omega * sqrt(-ldot/np->pdot);
 			scalecolor(ctmp, dtmp);
 			addcolor(cval, ctmp);
 		}
@@ -148,16 +156,27 @@ 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 */
 	setcolor(nd.mcolor, m->oargs.farg[0],
 			   m->oargs.farg[1],
@@ -167,52 +186,22 @@ 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 (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);
@@ -221,19 +210,15 @@ register RAY  *r;
 		if (nd.tspec > FTINY) {
 			nd.specfl |= SP_TRAN;
 							/* check threshold */
-			if (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
@@ -257,22 +242,55 @@ 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->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
@@ -282,7 +300,14 @@ 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
@@ -294,8 +319,13 @@ 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);
 }
 
 
@@ -309,6 +339,10 @@ register NORMDAT  *np;
 	double  rv[2];
 	double  d, sinp, cosp;
 	register int  i;
+					/* quick test */
+	if ((np->specfl & (SP_REFL|SP_RBLT)) != SP_REFL &&
+			(np->specfl & (SP_TRAN|SP_TBLT)) != SP_TRAN)
+		return;
 					/* set up sample coordinates */
 	v[0] = v[1] = v[2] = 0.0;
 	for (i = 0; i < 3; i++)
@@ -357,7 +391,7 @@ register NORMDAT  *np;
 		if (rv[1] <= FTINY)
 			d = 1.0;
 		else
-			d = sqrt( np->alpha2/4.0 * -log(rv[1]) );
+			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)