--- ray/src/rt/aniso.c	1995/11/06 12:03:20	2.30
+++ ray/src/rt/aniso.c	2014/01/25 18:27:39	2.56
@@ -1,38 +1,35 @@
-/* Copyright (c) 1992 Regents of the University of California */
-
 #ifndef lint
-static char SCCSid[] = "$SunId$ LBL";
+static const char RCSid[] = "$Id: aniso.c,v 2.56 2014/01/25 18:27:39 greg Exp $";
 #endif
-
 /*
  *  Shading functions for anisotropic materials.
  */
 
-#include  "ray.h"
+#include "copyright.h"
 
+#include  "ray.h"
+#include  "ambient.h"
 #include  "otypes.h"
-
+#include  "rtotypes.h"
+#include  "source.h"
 #include  "func.h"
-
 #include  "random.h"
 
-extern double  specthresh;		/* specular sampling threshold */
-extern double  specjitter;		/* specular sampling jitter */
+#ifndef  MAXITER
+#define  MAXITER	10		/* maximum # specular ray attempts */
+#endif
 
-extern int  backvis;			/* back faces visible? */
-
-static  agaussamp(), getacoords();
-
 /*
  *	This routine implements the anisotropic Gaussian
- *  model described by Ward in Siggraph `92 article.
+ *  model described by Ward in Siggraph `92 article, updated with
+ *  normalization and sampling adjustments due to Geisler-Moroder and Duer.
  *	We orient the surface towards the incoming ray, so a single
  *  surface can be used to represent an infinitely thin object.
  *
  *  Arguments for MAT_PLASTIC2 and MAT_METAL2 are:
  *  4+ ux	uy	uz	funcfile	[transform...]
  *  0
- *  6  red	grn	blu	specular-frac.	u-facet-slope v-facet-slope
+ *  6  red	grn	blu	specular-frac.	u-rough v-rough
  *
  *  Real arguments for MAT_TRANS2 are:
  *  8  red 	grn	blu	rspec	u-rough	v-rough	trans	tspec
@@ -64,13 +61,19 @@ typedef struct {
 	double  pdot;		/* perturbed dot product */
 }  ANISODAT;		/* anisotropic material data */
 
+static void getacoords(ANISODAT  *np);
+static void agaussamp(ANISODAT  *np);
 
-diraniso(cval, np, ldir, omega)		/* compute source contribution */
-COLOR  cval;			/* returned coefficient */
-register ANISODAT  *np;		/* material data */
-FVECT  ldir;			/* light source direction */
-double  omega;			/* light source size */
+
+static void
+diraniso(		/* compute source contribution */
+	COLOR  cval,			/* returned coefficient */
+	void  *nnp,			/* material data */
+	FVECT  ldir,			/* light source direction */
+	double  omega			/* light source size */
+)
 {
+	ANISODAT *np = nnp;
 	double  ldot;
 	double  dtmp, dtmp1, dtmp2;
 	FVECT  h;
@@ -84,57 +87,56 @@ double  omega;			/* light source size */
 	if (ldot < 0.0 ? np->trans <= FTINY : np->trans >= 1.0-FTINY)
 		return;		/* wrong side */
 
-	if (ldot > FTINY && np->rdiff > FTINY) {
+	if ((ldot > FTINY) & (np->rdiff > 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 * np->rdiff / PI;
+		dtmp = ldot * omega * np->rdiff * (1.0/PI);
 		scalecolor(ctmp, dtmp);
 		addcolor(cval, ctmp);
 	}
 	if (ldot > FTINY && (np->specfl&(SP_REFL|SP_BADU)) == SP_REFL) {
 		/*
 		 *  Compute specular reflection coefficient using
-		 *  anisotropic gaussian distribution model.
+		 *  anisotropic Gaussian distribution model.
 		 */
 						/* add source width if flat */
 		if (np->specfl & SP_FLAT)
-			au2 = av2 = omega/(4.0*PI);
+			au2 = av2 = omega * (0.25/PI);
 		else
 			au2 = av2 = 0.0;
 		au2 += np->u_alpha*np->u_alpha;
 		av2 += np->v_alpha*np->v_alpha;
 						/* half vector */
-		h[0] = ldir[0] - np->rp->rdir[0];
-		h[1] = ldir[1] - np->rp->rdir[1];
-		h[2] = ldir[2] - np->rp->rdir[2];
+		VSUB(h, ldir, np->rp->rdir);
 						/* ellipse */
 		dtmp1 = DOT(np->u, h);
 		dtmp1 *= dtmp1 / au2;
 		dtmp2 = DOT(np->v, h);
 		dtmp2 *= dtmp2 / av2;
-						/* gaussian */
+						/* new W-G-M-D model */
 		dtmp = DOT(np->pnorm, h);
-		dtmp = (dtmp1 + dtmp2) / (dtmp*dtmp);
-		dtmp = exp(-dtmp) * (0.25/PI)
-				* sqrt(ldot/(np->pdot*au2*av2));
+		dtmp *= dtmp;
+		dtmp1 = (dtmp1 + dtmp2) / dtmp;
+		dtmp = exp(-dtmp1) * DOT(h,h) /
+				(PI * dtmp*dtmp * sqrt(au2*av2));
 						/* 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) & (np->tdiff > FTINY)) {
 		/*
 		 *  Compute diffuse transmission.
 		 */
 		copycolor(ctmp, np->mcolor);
-		dtmp = -ldot * omega * np->tdiff / PI;
+		dtmp = -ldot * omega * np->tdiff * (1.0/PI);
 		scalecolor(ctmp, dtmp);
 		addcolor(cval, ctmp);
 	}
@@ -144,13 +146,11 @@ double  omega;			/* light source size */
 		 *  is always modified by material color.
 		 */
 						/* roughness + source */
-		au2 = av2 = omega / PI;
+		au2 = av2 = omega * (1.0/PI);
 		au2 += np->u_alpha*np->u_alpha;
 		av2 += np->v_alpha*np->v_alpha;
 						/* "half vector" */
-		h[0] = ldir[0] - np->prdir[0];
-		h[1] = ldir[1] - np->prdir[1];
-		h[2] = ldir[2] - np->prdir[2];
+		VSUB(h, ldir, np->prdir);
 		dtmp = DOT(h,h);
 		if (dtmp > FTINY*FTINY) {
 			dtmp1 = DOT(h,np->pnorm);
@@ -164,9 +164,8 @@ double  omega;			/* light source size */
 			}
 		} else
 			dtmp = 0.0;
-						/* gaussian */
-		dtmp = exp(-dtmp) * (1.0/PI)
-				* sqrt(-ldot/(np->pdot*au2*av2));
+						/* Gaussian */
+		dtmp = exp(-dtmp) * (1.0/PI) * sqrt(-ldot/(np->pdot*au2*av2));
 						/* worth using? */
 		if (dtmp > FTINY) {
 			copycolor(ctmp, np->mcolor);
@@ -178,22 +177,34 @@ double  omega;			/* light source size */
 }
 
 
-m_aniso(m, r)			/* shade ray that hit something anisotropic */
-register OBJREC  *m;
-register RAY  *r;
+int
+m_aniso(			/* shade ray that hit something anisotropic */
+	OBJREC  *m,
+	RAY  *r
+)
 {
 	ANISODAT  nd;
 	COLOR  ctmp;
-	register int  i;
+	int  i;
 						/* easy shadow test */
 	if (r->crtype & SHADOW)
 		return(1);
 
 	if (m->oargs.nfargs != (m->otype == MAT_TRANS2 ? 8 : 6))
 		objerror(m, USER, "bad number of real arguments");
+						/* check for back side */
+	if (r->rod < 0.0) {
+		if (!backvis) {
+			raytrans(r);
+			return(1);
+		}
+		raytexture(r, m->omod);
+		flipsurface(r);			/* reorient if backvis */
+	} else
+		raytexture(r, m->omod);
+						/* get material color */
 	nd.mp = m;
 	nd.rp = r;
-						/* get material color */
 	setcolor(nd.mcolor, m->oargs.farg[0],
 			   m->oargs.farg[1],
 			   m->oargs.farg[2]);
@@ -201,18 +212,9 @@ register RAY  *r;
 	nd.specfl = 0;
 	nd.u_alpha = m->oargs.farg[4];
 	nd.v_alpha = m->oargs.farg[5];
-	if (nd.u_alpha < FTINY || nd.v_alpha <= FTINY)
+	if ((nd.u_alpha <= FTINY) | (nd.v_alpha <= FTINY))
 		objerror(m, USER, "roughness too small");
-						/* check for back side */
-	if (r->rod < 0.0) {
-		if (!backvis && m->otype != MAT_TRANS2) {
-			raytrans(r);
-			return(1);
-		}
-		flipsurface(r);			/* reorient if backvis */
-	}
-						/* get modifiers */
-	raytexture(r, m->omod);
+
 	nd.pdot = raynormal(nd.pnorm, r);	/* perturb normal */
 	if (nd.pdot < .001)
 		nd.pdot = .001;			/* non-zero for diraniso() */
@@ -230,11 +232,9 @@ register RAY  *r;
 		if (specthresh >= nd.rspec-FTINY)
 			nd.specfl |= SP_RBLT;
 						/* compute refl. direction */
-		for (i = 0; i < 3; i++)
-			nd.vrefl[i] = r->rdir[i] + 2.0*nd.pdot*nd.pnorm[i];
+		VSUM(nd.vrefl, r->rdir, nd.pnorm, 2.0*nd.pdot);
 		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];
+			VSUM(nd.vrefl, r->rdir, r->ron, 2.0*r->rod);
 	}
 						/* compute transmission */
 	if (m->otype == MAT_TRANS2) {
@@ -266,28 +266,32 @@ register RAY  *r;
 	if (r->ro != NULL && isflat(r->ro->otype))
 		nd.specfl |= SP_FLAT;
 
-	getacoords(r, &nd);			/* set up coordinates */
+	getacoords(&nd);			/* set up coordinates */
 
 	if (nd.specfl & (SP_REFL|SP_TRAN) && !(nd.specfl & SP_BADU))
-		agaussamp(r, &nd);
+		agaussamp(&nd);
 
 	if (nd.rdiff > FTINY) {		/* ambient from this side */
-		ambient(ctmp, r, nd.pnorm);
-		if (nd.specfl & SP_RBLT)
-			scalecolor(ctmp, 1.0-nd.trans);
-		else
-			scalecolor(ctmp, nd.rdiff);
-		multcolor(ctmp, nd.mcolor);	/* modified by material color */
+		copycolor(ctmp, nd.mcolor);	/* modified by material color */
+		scalecolor(ctmp, nd.rdiff);
+		if (nd.specfl & SP_RBLT)	/* add in specular as well? */
+			addcolor(ctmp, nd.scolor);
+		multambient(ctmp, r, nd.pnorm);
 		addcolor(r->rcol, ctmp);	/* add to returned color */
 	}
 	if (nd.tdiff > FTINY) {		/* ambient from other side */
+		FVECT  bnorm;
+
 		flipsurface(r);
-		ambient(ctmp, r, nd.pnorm);
+		bnorm[0] = -nd.pnorm[0];
+		bnorm[1] = -nd.pnorm[1];
+		bnorm[2] = -nd.pnorm[2];
+		copycolor(ctmp, nd.mcolor);	/* modified by color */
 		if (nd.specfl & SP_TBLT)
 			scalecolor(ctmp, nd.trans);
 		else
 			scalecolor(ctmp, nd.tdiff);
-		multcolor(ctmp, nd.mcolor);	/* modified by color */
+		multambient(ctmp, r, bnorm);
 		addcolor(r->rcol, ctmp);
 		flipsurface(r);
 	}
@@ -298,26 +302,26 @@ register RAY  *r;
 }
 
 
-static
-getacoords(r, np)		/* set up coordinate system */
-RAY  *r;
-register ANISODAT  *np;
+static void
+getacoords(		/* set up coordinate system */
+	ANISODAT  *np
+)
 {
-	register MFUNC  *mf;
-	register int  i;
+	MFUNC  *mf;
+	int  i;
 
 	mf = getfunc(np->mp, 3, 0x7, 1);
-	setfunc(np->mp, r);
+	setfunc(np->mp, np->rp);
 	errno = 0;
 	for (i = 0; i < 3; i++)
 		np->u[i] = evalue(mf->ep[i]);
-	if (errno) {
+	if ((errno == EDOM) | (errno == ERANGE)) {
 		objerror(np->mp, WARNING, "compute error");
 		np->specfl |= SP_BADU;
 		return;
 	}
-	if (mf->f != &unitxf)
-		multv3(np->u, np->u, mf->f->xfm);
+	if (mf->fxp != &unitxf)
+		multv3(np->u, np->u, mf->fxp->xfm);
 	fcross(np->v, np->pnorm, np->u);
 	if (normalize(np->v) == 0.0) {
 		objerror(np->mp, WARNING, "illegal orientation vector");
@@ -328,78 +332,140 @@ register ANISODAT  *np;
 }
 
 
-static
-agaussamp(r, np)		/* sample anisotropic gaussian specular */
-RAY  *r;
-register ANISODAT  *np;
+static void
+agaussamp(		/* sample anisotropic Gaussian specular */
+	ANISODAT  *np
+)
 {
 	RAY  sr;
 	FVECT  h;
 	double  rv[2];
 	double  d, sinp, cosp;
-	register int  i;
+	COLOR	scol;
+	int  maxiter, ntrials, nstarget, nstaken;
+	int  i;
 					/* compute reflection */
 	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) * np->u_alpha;
-		sinp = sin(d) * np->v_alpha;
-		d = sqrt(cosp*cosp + sinp*sinp);
-		cosp /= d;
-		sinp /= d;
-		rv[1] = 1.0 - specjitter*rv[1];
-		if (rv[1] <= FTINY)
-			d = 1.0;
-		else
-			d = sqrt(-log(rv[1]) /
-				(cosp*cosp/(np->u_alpha*np->u_alpha) +
-				 sinp*sinp/(np->v_alpha*np->v_alpha)));
-		for (i = 0; i < 3; i++)
-			h[i] = np->pnorm[i] +
-				d*(cosp*np->u[i] + sinp*np->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)	/* penetration? */
-			VCOPY(sr.rdir, np->vrefl);	/* jitter no good */
-		rayvalue(&sr);
-		multcolor(sr.rcol, np->scolor);
-		addcolor(r->rcol, sr.rcol);
+			rayorigin(&sr, SPECULAR, np->rp, np->scolor) == 0) {
+		nstarget = 1;
+		if (specjitter > 1.5) {	/* multiple samples? */
+			nstarget = specjitter*np->rp->rweight + .5;
+			if (sr.rweight <= minweight*nstarget)
+				nstarget = sr.rweight/minweight;
+			if (nstarget > 1) {
+				d = 1./nstarget;
+				scalecolor(sr.rcoef, d);
+				sr.rweight *= d;
+			} else
+				nstarget = 1;
+		}
+		setcolor(scol, 0., 0., 0.);
+		dimlist[ndims++] = (int)(size_t)np->mp;
+		maxiter = MAXITER*nstarget;
+		for (nstaken = ntrials = 0; nstaken < nstarget &&
+						ntrials < maxiter; ntrials++) {
+			if (ntrials)
+				d = frandom();
+			else
+				d = urand(ilhash(dimlist,ndims)+samplendx);
+			multisamp(rv, 2, d);
+			d = 2.0*PI * rv[0];
+			cosp = tcos(d) * np->u_alpha;
+			sinp = tsin(d) * np->v_alpha;
+			d = 1./sqrt(cosp*cosp + sinp*sinp);
+			cosp *= d;
+			sinp *= d;
+			if ((0. <= specjitter) & (specjitter < 1.))
+				rv[1] = 1.0 - specjitter*rv[1];
+			if (rv[1] <= FTINY)
+				d = 1.0;
+			else
+				d = sqrt(-log(rv[1]) /
+					(cosp*cosp/(np->u_alpha*np->u_alpha) +
+					 sinp*sinp/(np->v_alpha*np->v_alpha)));
+			for (i = 0; i < 3; i++)
+				h[i] = np->pnorm[i] +
+					d*(cosp*np->u[i] + sinp*np->v[i]);
+			d = -2.0 * DOT(h, np->rp->rdir) / (1.0 + d*d);
+			VSUM(sr.rdir, np->rp->rdir, h, d);
+						/* sample rejection test */
+			if ((d = DOT(sr.rdir, np->rp->ron)) <= FTINY)
+				continue;
+			checknorm(sr.rdir);
+			if (nstarget > 1) {	/* W-G-M-D adjustment */
+				if (nstaken) rayclear(&sr);
+				rayvalue(&sr);
+				d = 2./(1. + np->rp->rod/d);
+				scalecolor(sr.rcol, d);
+				addcolor(scol, sr.rcol);
+			} else {
+				rayvalue(&sr);
+				multcolor(sr.rcol, sr.rcoef);
+				addcolor(np->rp->rcol, sr.rcol);
+			}
+			++nstaken;
+		}
+		if (nstarget > 1) {		/* final W-G-M-D weighting */
+			multcolor(scol, sr.rcoef);
+			d = (double)nstarget/ntrials;
+			scalecolor(scol, d);
+			addcolor(np->rp->rcol, scol);
+		}
 		ndims--;
 	}
 					/* compute transmission */
+	copycolor(sr.rcoef, np->mcolor);		/* modify by material color */
+	scalecolor(sr.rcoef, np->tspec);
 	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) * np->u_alpha;
-		sinp = sin(d) * np->v_alpha;
-		d = sqrt(cosp*cosp + sinp*sinp);
-		cosp /= d;
-		sinp /= d;
-		rv[1] = 1.0 - specjitter*rv[1];
-		if (rv[1] <= FTINY)
-			d = 1.0;
-		else
-			d = sqrt(-log(rv[1]) /
-				(cosp*cosp/(np->u_alpha*np->u_alpha) +
-				 sinp*sinp/(np->v_alpha*np->u_alpha)));
-		for (i = 0; i < 3; i++)
-			sr.rdir[i] = np->prdir[i] +
-					d*(cosp*np->u[i] + sinp*np->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);		/* modify by color */
-		addcolor(r->rcol, sr.rcol);
+			rayorigin(&sr, SPECULAR, np->rp, sr.rcoef) == 0) {
+		nstarget = 1;
+		if (specjitter > 1.5) {	/* multiple samples? */
+			nstarget = specjitter*np->rp->rweight + .5;
+			if (sr.rweight <= minweight*nstarget)
+				nstarget = sr.rweight/minweight;
+			if (nstarget > 1) {
+				d = 1./nstarget;
+				scalecolor(sr.rcoef, d);
+				sr.rweight *= d;
+			} else
+				nstarget = 1;
+		}
+		dimlist[ndims++] = (int)(size_t)np->mp;
+		maxiter = MAXITER*nstarget;
+		for (nstaken = ntrials = 0; nstaken < nstarget &&
+						ntrials < maxiter; ntrials++) {
+			if (ntrials)
+				d = frandom();
+			else
+				d = urand(ilhash(dimlist,ndims)+1823+samplendx);
+			multisamp(rv, 2, d);
+			d = 2.0*PI * rv[0];
+			cosp = tcos(d) * np->u_alpha;
+			sinp = tsin(d) * np->v_alpha;
+			d = 1./sqrt(cosp*cosp + sinp*sinp);
+			cosp *= d;
+			sinp *= d;
+			if ((0. <= specjitter) & (specjitter < 1.))
+				rv[1] = 1.0 - specjitter*rv[1];
+			if (rv[1] <= FTINY)
+				d = 1.0;
+			else
+				d = sqrt(-log(rv[1]) /
+					(cosp*cosp/(np->u_alpha*np->u_alpha) +
+					 sinp*sinp/(np->v_alpha*np->v_alpha)));
+			for (i = 0; i < 3; i++)
+				sr.rdir[i] = np->prdir[i] +
+						d*(cosp*np->u[i] + sinp*np->v[i]);
+			if (DOT(sr.rdir, np->rp->ron) >= -FTINY)
+				continue;
+			normalize(sr.rdir);	/* OK, normalize */
+			if (nstaken)		/* multi-sampling */
+				rayclear(&sr);
+			rayvalue(&sr);
+			multcolor(sr.rcol, sr.rcoef);
+			addcolor(np->rp->rcol, sr.rcol);
+			++nstaken;
+		}
 		ndims--;
 	}
 }