--- ray/src/rt/normal.c	1991/06/13 13:58:18	1.11
+++ ray/src/rt/normal.c	1992/01/15 11:02:40	2.6
@@ -1,4 +1,4 @@
-/* Copyright (c) 1991 Regents of the University of California */
+/* Copyright (c) 1992 Regents of the University of California */
 
 #ifndef lint
 static char SCCSid[] = "$SunId$ LBL";
@@ -11,12 +11,18 @@ static char SCCSid[] = "$SunId$ LBL";
  *     12/19/85 - added stuff for metals.
  *     6/26/87 - improved specular model.
  *     9/28/87 - added model for translucent materials.
+ *     Later changes described in delta comments.
  */
 
 #include  "ray.h"
 
 #include  "otypes.h"
 
+#include  "random.h"
+
+extern double  specthresh;		/* specular sampling threshold */
+extern double  specjitter;		/* specular sampling jitter */
+
 /*
  *	This routine uses portions of the reflection
  *  model described by Cook and Torrance.
@@ -34,15 +40,22 @@ static char SCCSid[] = "$SunId$ LBL";
 
 #define  BSPEC(m)	(6.0)		/* specularity parameter b */
 
-extern double  exp();
+				/* specularity flags */
+#define  SP_REFL	01		/* has reflected specular component */
+#define  SP_TRAN	02		/* has transmitted specular */
+#define  SP_PURE	010		/* purely specular (zero roughness) */
+#define  SP_FLAT	020		/* flat reflecting surface */
+#define  SP_RBLT	040		/* reflection below sample threshold */
+#define  SP_TBLT	0100		/* transmission below threshold */
 
 typedef struct {
 	OBJREC  *mp;		/* material pointer */
-	RAY  *pr;		/* intersected ray */
+	short  specfl;		/* specularity flags, defined above */
 	COLOR  mcolor;		/* color of this material */
 	COLOR  scolor;		/* color of specular component */
 	FVECT  vrefl;		/* vector in direction of reflected ray */
-	double  alpha2;		/* roughness squared times 2 */
+	FVECT  prdir;		/* vector in transmitted direction */
+	double  alpha2;		/* roughness squared */
 	double  rdiff, rspec;	/* reflected specular, diffuse */
 	double  trans;		/* transmissivity */
 	double  tdiff, tspec;	/* transmitted specular, diffuse */
@@ -59,6 +72,7 @@ double  omega;			/* light source size */
 {
 	double  ldot;
 	double  dtmp;
+	int	i;
 	COLOR  ctmp;
 
 	setcolor(cval, 0.0, 0.0, 0.0);
@@ -79,19 +93,22 @@ double  omega;			/* light source size */
 		scalecolor(ctmp, dtmp);
 		addcolor(cval, ctmp);
 	}
-	if (ldot > FTINY && np->rspec > FTINY && np->alpha2 > FTINY) {
+	if (ldot > FTINY && (np->specfl&(SP_REFL|SP_PURE)) == SP_REFL) {
 		/*
 		 *  Compute specular reflection coefficient using
 		 *  gaussian distribution model.
 		 */
-						/* roughness + source */
-		dtmp = np->alpha2 + omega/(2.0*PI);
+						/* roughness */
+		dtmp = 2.0*np->alpha2;
+						/* + source if flat */
+		if (np->specfl & SP_FLAT)
+			dtmp += omega/(2.0*PI);
 						/* gaussian */
 		dtmp = exp((DOT(np->vrefl,ldir)-1.)/dtmp)/(2.*PI)/dtmp;
 						/* worth using? */
 		if (dtmp > FTINY) {
 			copycolor(ctmp, np->scolor);
-			dtmp *= omega;
+			dtmp *= omega / np->pdot;
 			scalecolor(ctmp, dtmp);
 			addcolor(cval, ctmp);
 		}
@@ -105,26 +122,27 @@ double  omega;			/* light source size */
 		scalecolor(ctmp, dtmp);
 		addcolor(cval, ctmp);
 	}
-	if (ldot < -FTINY && np->tspec > FTINY && np->alpha2 > FTINY) {
+	if (ldot < -FTINY && (np->specfl&(SP_TRAN|SP_PURE)) == SP_TRAN) {
 		/*
 		 *  Compute specular transmission.  Specular transmission
-		 *  is unaffected by material color.
+		 *  is always modified by material color.
 		 */
 						/* roughness + source */
 		dtmp = np->alpha2 + omega/(2.0*PI);
 						/* gaussian */
-		dtmp = exp((DOT(np->pr->rdir,ldir)-1.)/dtmp)/(2.*PI)/dtmp;
+		dtmp = exp((DOT(np->prdir,ldir)-1.)/dtmp)/(2.*PI)/dtmp;
 						/* worth using? */
 		if (dtmp > FTINY) {
-			dtmp *= np->tspec * omega;
-			setcolor(ctmp, dtmp, dtmp, dtmp);
+			copycolor(ctmp, np->mcolor);
+			dtmp *= np->tspec * omega / np->pdot;
+			scalecolor(ctmp, dtmp);
 			addcolor(cval, ctmp);
 		}
 	}
 }
 
 
-m_normal(m, r)			/* color a ray which hit something normal */
+m_normal(m, r)			/* color a ray that hit something normal */
 register OBJREC  *m;
 register RAY  *r;
 {
@@ -133,33 +151,35 @@ register RAY  *r;
 	double  dtmp;
 	COLOR  ctmp;
 	register int  i;
-
-	if (m->oargs.nfargs != (m->otype == MAT_TRANS ? 7 : 5))
-		objerror(m, USER, "bad # arguments");
 						/* easy shadow test */
 	if (r->crtype & SHADOW && m->otype != MAT_TRANS)
 		return;
+
+	if (m->oargs.nfargs != (m->otype == MAT_TRANS ? 7 : 5))
+		objerror(m, USER, "bad number of arguments");
 	nd.mp = m;
-	nd.pr = r;
 						/* get material color */
 	setcolor(nd.mcolor, m->oargs.farg[0],
 			   m->oargs.farg[1],
 			   m->oargs.farg[2]);
 						/* get roughness */
+	nd.specfl = 0;
 	nd.alpha2 = m->oargs.farg[4];
-	nd.alpha2 *= 2.0 * nd.alpha2;
+	if ((nd.alpha2 *= nd.alpha2) <= FTINY)
+		nd.specfl |= SP_PURE;
 						/* reorient if necessary */
 	if (r->rod < 0.0)
 		flipsurface(r);
 						/* get modifiers */
 	raytexture(r, m->omod);
 	nd.pdot = raynormal(nd.pnorm, r);	/* perturb normal */
+	if (nd.pdot < .001)
+		nd.pdot = .001;			/* non-zero for dirnorm() */
 	multcolor(nd.mcolor, r->pcol);		/* modify material color */
 	transtest = 0;
 						/* get specular component */
-	nd.rspec = m->oargs.farg[3];
-
-	if (nd.rspec > FTINY) {			/* has 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);
@@ -171,11 +191,17 @@ register RAY  *r;
 		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 + (.1 - .2*urand(8199+samplendx))
+					> 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 (nd.alpha2 <= FTINY && !(r->crtype & SHADOW)) {
+		if (!(r->crtype & SHADOW) && nd.specfl & SP_PURE) {
 			RAY  lr;
 			if (rayorigin(&lr, r, REFLECTED, nd.rspec) == 0) {
 				VCOPY(lr.rdir, nd.vrefl);
@@ -190,21 +216,33 @@ register RAY  *r;
 		nd.trans = m->oargs.farg[5]*(1.0 - nd.rspec);
 		nd.tspec = nd.trans * m->oargs.farg[6];
 		nd.tdiff = nd.trans - nd.tspec;
+		if (nd.tspec > FTINY) {
+			nd.specfl |= SP_TRAN;
+							/* check threshold */
+			if (specthresh > FTINY &&
+					((specthresh >= 1.-FTINY ||
+					specthresh +
+					    (.1 - .2*urand(7241+samplendx))
+						> nd.tspec)))
+				nd.specfl |= SP_TBLT;
+			if (r->crtype & SHADOW ||
+					DOT(r->pert,r->pert) <= FTINY*FTINY) {
+				VCOPY(nd.prdir, r->rdir);
+				transtest = 2;
+			} else {
+				for (i = 0; i < 3; i++)		/* perturb */
+					nd.prdir[i] = r->rdir[i] -
+							.75*r->pert[i];
+				normalize(nd.prdir);
+			}
+		}
 	} else
 		nd.tdiff = nd.tspec = nd.trans = 0.0;
 						/* transmitted ray */
-	if (nd.tspec > FTINY && nd.alpha2 <= FTINY) {
+	if ((nd.specfl&(SP_TRAN|SP_PURE)) == (SP_TRAN|SP_PURE)) {
 		RAY  lr;
 		if (rayorigin(&lr, r, TRANS, nd.tspec) == 0) {
-			if (DOT(r->pert,r->pert) > FTINY*FTINY) {
-				for (i = 0; i < 3; i++)	/* perturb direction */
-					lr.rdir[i] = r->rdir[i] -
-							.75*r->pert[i];
-				normalize(lr.rdir);
-			} else {
-				VCOPY(lr.rdir, r->rdir);
-				transtest = 2;
-			}
+			VCOPY(lr.rdir, nd.prdir);
 			rayvalue(&lr);
 			scalecolor(lr.rcol, nd.tspec);
 			multcolor(lr.rcol, nd.mcolor);	/* modified by color */
@@ -213,31 +251,38 @@ register RAY  *r;
 			transdist = r->rot + lr.rt;
 		}
 	}
+
 	if (r->crtype & SHADOW)			/* the rest is shadow */
 		return;
 						/* diffuse reflection */
 	nd.rdiff = 1.0 - nd.trans - nd.rspec;
 
-	if (nd.rdiff <= FTINY && nd.tdiff <= FTINY && nd.alpha2 <= FTINY)
-		return;				/* purely specular */
+	if (nd.specfl & SP_PURE && nd.rdiff <= FTINY && nd.tdiff <= FTINY)
+		return;				/* 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);
-		if (nd.alpha2 <= FTINY)
-			scalecolor(ctmp, nd.rdiff);
-		else
+		if (nd.specfl & SP_RBLT)
 			scalecolor(ctmp, 1.0-nd.trans);
+		else
+			scalecolor(ctmp, nd.rdiff);
 		multcolor(ctmp, nd.mcolor);	/* modified by material color */
 		addcolor(r->rcol, ctmp);	/* add to returned color */
 	}
 	if (nd.tdiff > FTINY) {		/* ambient from other side */
 		flipsurface(r);
 		ambient(ctmp, r);
-		if (nd.alpha2 <= FTINY)
-			scalecolor(ctmp, nd.tdiff);
-		else
+		if (nd.specfl & SP_TBLT)
 			scalecolor(ctmp, nd.trans);
-		multcolor(ctmp, nd.mcolor);
+		else
+			scalecolor(ctmp, nd.tdiff);
+		multcolor(ctmp, nd.mcolor);	/* modified by color */
 		addcolor(r->rcol, ctmp);
 		flipsurface(r);
 	}
@@ -246,4 +291,58 @@ register RAY  *r;
 					/* check distance */
 	if (transtest > bright(r->rcol))
 		r->rt = transdist;
+}
+
+
+static
+gaussamp(r, np)			/* sample gaussian specular */
+RAY  *r;
+register NORMDAT  *np;
+{
+	RAY  sr;
+	FVECT  u, v, h;
+	double  rv[2];
+	double  d, sinp, cosp;
+	int  ntries;
+	register int  i;
+					/* set up sample coordinates */
+	v[0] = v[1] = v[2] = 0.0;
+	for (i = 0; i < 3; i++)
+		if (np->pnorm[i] < 0.6 && np->pnorm[i] > -0.6)
+			break;
+	v[i] = 1.0;
+	fcross(u, v, np->pnorm);
+	normalize(u);
+	fcross(v, np->pnorm, u);
+					/* compute reflection */
+	if ((np->specfl & (SP_REFL|SP_RBLT)) == SP_REFL &&
+			rayorigin(&sr, r, SPECULAR, np->rspec) == 0) {
+		dimlist[ndims++] = (int)np->mp;
+		for (ntries = 0; ntries < 10; ntries++) {
+			dimlist[ndims] = ntries * 8912;
+			d = urand(ilhash(dimlist,ndims+1)+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 */
 }