--- ray/src/rt/normal.c	2004/09/20 17:32:04	2.48
+++ ray/src/rt/normal.c	2010/10/10 22:31:46	2.57
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: normal.c,v 2.48 2004/09/20 17:32:04 greg Exp $";
+static const char RCSid[] = "$Id: normal.c,v 2.57 2010/10/10 22:31:46 greg Exp $";
 #endif
 /*
  *  normal.c - shading function for normal materials.
@@ -25,6 +25,7 @@ static const char RCSid[] = "$Id: normal.c,v 2.48 2004
 #endif
 					/* estimate of Fresnel function */
 #define  FRESNE(ci)	(exp(-5.85*(ci)) - 0.00287989916)
+#define  FRESTHRESH	0.017999	/* minimum specularity for approx. */
 
 
 /*
@@ -78,8 +79,8 @@ dirnorm(		/* compute source contribution */
 {
 	register NORMDAT *np = nnp;
 	double  ldot;
-	double  ldiff;
-	double  dtmp, d2;
+	double  lrdiff, ltdiff;
+	double  dtmp, d2, d3, d4;
 	FVECT  vtmp;
 	COLOR  ctmp;
 
@@ -91,25 +92,30 @@ dirnorm(		/* compute source contribution */
 		return;		/* wrong side */
 
 				/* Fresnel estimate */
-	ldiff = np->rdiff;
-	if (np->specfl & SP_PURE && (np->rspec > FTINY) & (ldiff > FTINY))
-		ldiff *= 1. - FRESNE(fabs(ldot));
+	lrdiff = np->rdiff;
+	ltdiff = np->tdiff;
+	if (np->specfl & SP_PURE && np->rspec >= FRESTHRESH &&
+			(lrdiff > FTINY) | (ltdiff > FTINY)) {
+		dtmp = 1. - FRESNE(fabs(ldot));
+		lrdiff *= dtmp;
+		ltdiff *= dtmp;
+	}
 
-	if (ldot > FTINY && ldiff > FTINY) {
+	if (ldot > FTINY && lrdiff > FTINY) {
 		/*
 		 *  Compute and add diffuse reflected component to returned
 		 *  color.  The diffuse reflected component will always be
 		 *  modified by the color of the material.
 		 */
 		copycolor(ctmp, np->mcolor);
-		dtmp = ldot * omega * ldiff * (1.0/PI);
+		dtmp = ldot * omega * lrdiff * (1.0/PI);
 		scalecolor(ctmp, dtmp);
 		addcolor(cval, ctmp);
 	}
 	if (ldot > FTINY && (np->specfl&(SP_REFL|SP_PURE)) == SP_REFL) {
 		/*
 		 *  Compute specular reflection coefficient using
-		 *  gaussian distribution model.
+		 *  Gaussian distribution model.
 		 */
 						/* roughness */
 		dtmp = np->alpha2;
@@ -122,23 +128,24 @@ dirnorm(		/* compute source contribution */
 		vtmp[2] = ldir[2] - np->rp->rdir[2];
 		d2 = DOT(vtmp, np->pnorm);
 		d2 *= d2;
-		d2 = (DOT(vtmp,vtmp) - d2) / d2;
-						/* gaussian */
-		dtmp = exp(-d2/dtmp)/(4.*PI * np->pdot * dtmp);
+		d3 = DOT(vtmp,vtmp);
+		d4 = (d3 - d2) / d2;
+						/* new W-G-M-D model */
+		dtmp = exp(-d4/dtmp) * d3 / (PI * d2*d2 * dtmp);
 						/* worth using? */
 		if (dtmp > FTINY) {
 			copycolor(ctmp, np->scolor);
-			dtmp *= omega;
+			dtmp *= ldot * omega;
 			scalecolor(ctmp, dtmp);
 			addcolor(cval, ctmp);
 		}
 	}
-	if (ldot < -FTINY && np->tdiff > FTINY) {
+	if (ldot < -FTINY && ltdiff > FTINY) {
 		/*
 		 *  Compute diffuse transmission.
 		 */
 		copycolor(ctmp, np->mcolor);
-		dtmp = -ldot * omega * np->tdiff * (1.0/PI);
+		dtmp = -ldot * omega * ltdiff * (1.0/PI);
 		scalecolor(ctmp, dtmp);
 		addcolor(cval, ctmp);
 	}
@@ -149,13 +156,12 @@ dirnorm(		/* compute source contribution */
 		 */
 						/* roughness + source */
 		dtmp = np->alpha2 + omega*(1.0/PI);
-						/* gaussian */
-		dtmp = exp((2.*DOT(np->prdir,ldir)-2.)/dtmp) /
-					(PI*np->pdot*dtmp);
+						/* Gaussian */
+		dtmp = exp((2.*DOT(np->prdir,ldir)-2.)/dtmp)/(PI*dtmp);
 						/* worth using? */
 		if (dtmp > FTINY) {
 			copycolor(ctmp, np->mcolor);
-			dtmp *= np->tspec * omega;
+			dtmp *= np->tspec * omega * sqrt(-ldot/np->pdot);
 			scalecolor(ctmp, dtmp);
 			addcolor(cval, ctmp);
 		}
@@ -220,7 +226,7 @@ m_normal(			/* color a ray that hit something normal *
 	mirdist = transdist = r->rot;
 	nd.rspec = m->oargs.farg[3];
 						/* compute Fresnel approx. */
-	if (nd.specfl & SP_PURE && nd.rspec > FTINY) {
+	if (nd.specfl & SP_PURE && nd.rspec >= FRESTHRESH) {
 		fest = FRESNE(r->rod);
 		nd.rspec += fest*(1. - nd.rspec);
 	} else
@@ -253,11 +259,12 @@ m_normal(			/* color a ray that hit something normal *
 						/* transmitted ray */
 	if ((nd.specfl&(SP_TRAN|SP_PURE|SP_TBLT)) == (SP_TRAN|SP_PURE)) {
 		RAY  lr;
-		if (rayorigin(&lr, r, TRANS, nd.tspec) == 0) {
+		copycolor(lr.rcoef, nd.mcolor);	/* modified by color */
+		scalecolor(lr.rcoef, nd.tspec);
+		if (rayorigin(&lr, TRANS, r, lr.rcoef) == 0) {
 			VCOPY(lr.rdir, nd.prdir);
 			rayvalue(&lr);
-			scalecolor(lr.rcol, nd.tspec);
-			multcolor(lr.rcol, nd.mcolor);	/* modified by color */
+			multcolor(lr.rcol, lr.rcoef);
 			addcolor(r->rcol, lr.rcol);
 			transtest *= bright(lr.rcol);
 			transdist = r->rot + lr.rt;
@@ -287,20 +294,19 @@ m_normal(			/* color a ray that hit something normal *
 		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];
+		VSUM(nd.vrefl, r->rdir, nd.pnorm, 2.*nd.pdot);
 						/* 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];
+			VSUM(nd.vrefl, r->rdir, r->ron, 2.*r->rod);
+		checknorm(nd.vrefl);
 	}
 						/* reflected ray */
 	if ((nd.specfl&(SP_REFL|SP_PURE|SP_RBLT)) == (SP_REFL|SP_PURE)) {
 		RAY  lr;
-		if (rayorigin(&lr, r, REFLECTED, nd.rspec) == 0) {
+		if (rayorigin(&lr, REFLECTED, r, nd.scolor) == 0) {
 			VCOPY(lr.rdir, nd.vrefl);
 			rayvalue(&lr);
-			multcolor(lr.rcol, nd.scolor);
+			multcolor(lr.rcol, lr.rcoef);
 			addcolor(r->rcol, lr.rcol);
 			if (!hastexture && nd.specfl & SP_FLAT) {
 				mirtest = 2.*bright(lr.rcol);
@@ -318,29 +324,29 @@ m_normal(			/* color a ray that hit something normal *
 		gaussamp(r, &nd);		/* checks *BLT flags */
 
 	if (nd.rdiff > FTINY) {		/* ambient from this side */
-		ambient(ctmp, r, hastexture?nd.pnorm:r->ron);
+		copycolor(ctmp, nd.mcolor);	/* modified by material color */
 		if (nd.specfl & SP_RBLT)
 			scalecolor(ctmp, 1.0-nd.trans);
 		else
 			scalecolor(ctmp, nd.rdiff);
-		multcolor(ctmp, nd.mcolor);	/* modified by material color */
+		multambient(ctmp, r, hastexture ? nd.pnorm : r->ron);
 		addcolor(r->rcol, ctmp);	/* add to returned color */
 	}
 	if (nd.tdiff > FTINY) {		/* ambient from other side */
+		copycolor(ctmp, nd.mcolor);	/* modified by color */
+		if (nd.specfl & SP_TBLT)
+			scalecolor(ctmp, nd.trans);
+		else
+			scalecolor(ctmp, nd.tdiff);
 		flipsurface(r);
 		if (hastexture) {
 			FVECT  bnorm;
 			bnorm[0] = -nd.pnorm[0];
 			bnorm[1] = -nd.pnorm[1];
 			bnorm[2] = -nd.pnorm[2];
-			ambient(ctmp, r, bnorm);
+			multambient(ctmp, r, bnorm);
 		} else
-			ambient(ctmp, r, r->ron);
-		if (nd.specfl & SP_TBLT)
-			scalecolor(ctmp, nd.trans);
-		else
-			scalecolor(ctmp, nd.tdiff);
-		multcolor(ctmp, nd.mcolor);	/* modified by color */
+			multambient(ctmp, r, r->ron);
 		addcolor(r->rcol, ctmp);
 		flipsurface(r);
 	}
@@ -358,7 +364,7 @@ m_normal(			/* color a ray that hit something normal *
 
 
 static void
-gaussamp(			/* sample gaussian specular */
+gaussamp(			/* sample Gaussian specular */
 	RAY  *r,
 	register NORMDAT  *np
 )
@@ -367,7 +373,8 @@ gaussamp(			/* sample gaussian specular */
 	FVECT  u, v, h;
 	double  rv[2];
 	double  d, sinp, cosp;
-	int  niter;
+	COLOR	scol;
+	int  niter, ns2go;
 	register int  i;
 					/* quick test */
 	if ((np->specfl & (SP_REFL|SP_RBLT)) != SP_REFL &&
@@ -384,10 +391,23 @@ gaussamp(			/* sample gaussian specular */
 	fcross(v, np->pnorm, u);
 					/* compute reflection */
 	if ((np->specfl & (SP_REFL|SP_RBLT)) == SP_REFL &&
-			rayorigin(&sr, r, SPECULAR, np->rspec) == 0) {
+			rayorigin(&sr, SPECULAR, r, np->scolor) == 0) {
+		copycolor(scol, np->scolor);
+		ns2go = 1;
+		if (specjitter > 1.5) {	/* multiple samples? */
+			ns2go = specjitter*r->rweight + .5;
+			if (sr.rweight <= minweight*ns2go)
+				ns2go = sr.rweight/minweight;
+			if (ns2go > 1) {
+				d = 1./ns2go;
+				scalecolor(scol, d);
+				sr.rweight *= d;
+			} else
+				ns2go = 1;
+		}
 		dimlist[ndims++] = (int)np->mp;
-		for (niter = 0; niter < MAXITER; niter++) {
-			if (niter)
+		for (niter = ns2go*MAXITER; (ns2go > 0) & (niter > 0); niter--) {
+			if (specjitter > 1.5)
 				d = frandom();
 			else
 				d = urand(ilhash(dimlist,ndims)+samplendx);
@@ -395,7 +415,8 @@ gaussamp(			/* sample gaussian specular */
 			d = 2.0*PI * rv[0];
 			cosp = tcos(d);
 			sinp = tsin(d);
-			rv[1] = 1.0 - specjitter*rv[1];
+			if ((0. <= specjitter) & (specjitter < 1.))
+				rv[1] = 1.0 - specjitter*rv[1];
 			if (rv[1] <= FTINY)
 				d = 1.0;
 			else
@@ -403,23 +424,45 @@ gaussamp(			/* sample gaussian specular */
 			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;
+			if (d <= np->pdot + FTINY)
+				continue;
+			VSUM(sr.rdir, r->rdir, h, d);
+			if (DOT(sr.rdir, r->ron) <= FTINY)
+				continue;
+			checknorm(sr.rdir);
+			if (specjitter > 1.5) {	/* adjusted W-G-M-D weight */
+				d = 2.*(1. - np->pdot/d);
+				copycolor(sr.rcoef, scol);
+				scalecolor(sr.rcoef, d);
+				rayclear(&sr);
 			}
+			rayvalue(&sr);
+			multcolor(sr.rcol, sr.rcoef);
+			addcolor(r->rcol, sr.rcol);
+			--ns2go;
 		}
 		ndims--;
 	}
 					/* compute transmission */
+	copycolor(sr.rcoef, np->mcolor);	/* modified by color */
+	scalecolor(sr.rcoef, np->tspec);
 	if ((np->specfl & (SP_TRAN|SP_TBLT)) == SP_TRAN &&
-			rayorigin(&sr, r, SPECULAR, np->tspec) == 0) {
+			rayorigin(&sr, SPECULAR, r, sr.rcoef) == 0) {
+		ns2go = 1;
+		if (specjitter > 1.5) {	/* multiple samples? */
+			ns2go = specjitter*r->rweight + .5;
+			if (sr.rweight <= minweight*ns2go)
+				ns2go = sr.rweight/minweight;
+			if (ns2go > 1) {
+				d = 1./ns2go;
+				scalecolor(sr.rcoef, d);
+				sr.rweight *= d;
+			} else
+				ns2go = 1;
+		}
 		dimlist[ndims++] = (int)np->mp;
-		for (niter = 0; niter < MAXITER; niter++) {
-			if (niter)
+		for (niter = ns2go*MAXITER; (ns2go > 0) & (niter > 0); niter--) {
+			if (specjitter > 1.5)
 				d = frandom();
 			else
 				d = urand(ilhash(dimlist,ndims)+1823+samplendx);
@@ -427,21 +470,23 @@ gaussamp(			/* sample gaussian specular */
 			d = 2.0*PI * rv[0];
 			cosp = tcos(d);
 			sinp = tsin(d);
-			rv[1] = 1.0 - specjitter*rv[1];
+			if ((0. <= specjitter) & (specjitter < 1.))
+				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++)
 				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;
-			}
+			if (DOT(sr.rdir, r->ron) >= -FTINY)
+				continue;
+			normalize(sr.rdir);	/* OK, normalize */
+			if (specjitter > 1.5)	/* multi-sampling */
+				rayclear(&sr);
+			rayvalue(&sr);
+			multcolor(sr.rcol, sr.rcoef);
+			addcolor(r->rcol, sr.rcol);
+			--ns2go;
 		}
 		ndims--;
 	}