src/rt/m_bsdf.c

#ifndef lint
static const char RCSid[] = "$Id: m_bsdf.c,v 2.25 2014/01/22 16:39:57 greg Exp $";
#endif
/*
 *  Shading for materials with BSDFs taken from XML data files
 */

#include "copyright.h"

#include  "ray.h"
#include  "ambient.h"
#include  "source.h"
#include  "func.h"
#include  "bsdf.h"
#include  "random.h"

/*
 *      Arguments to this material include optional diffuse colors.
 *  String arguments include the BSDF and function files.
 *      A non-zero thickness causes the strange but useful behavior
 *  of translating transmitted rays this distance beneath the surface
 *  (opposite the surface normal) to bypass any intervening geometry.
 *  Translation only affects scattered, non-source-directed samples.
 *  A non-zero thickness has the further side-effect that an unscattered
 *  (view) ray will pass right through our material if it has any
 *  non-diffuse transmission, making the BSDF surface invisible.  This
 *  shows the proxied geometry instead. Thickness has the further
 *  effect of turning off reflection on the hidden side so that rays
 *  heading in the opposite direction pass unimpeded through the BSDF
 *  surface.  A paired surface may be placed on the opposide side of
 *  the detail geometry, less than this thickness away, if a two-way
 *  proxy is desired.  Note that the sign of the thickness is important.
 *  A positive thickness hides geometry behind the BSDF surface and uses
 *  front reflectance and transmission properties.  A negative thickness
 *  hides geometry in front of the surface when rays hit from behind,
 *  and applies only the transmission and backside reflectance properties.
 *  Reflection is ignored on the hidden side, as those rays pass through.
 *      The "up" vector for the BSDF is given by three variables, defined
 *  (along with the thickness) by the named function file, or '.' if none.
 *  Together with the surface normal, this defines the local coordinate
 *  system for the BSDF.
 *      We do not reorient the surface, so if the BSDF has no back-side
 *  reflectance and none is given in the real arguments, a BSDF surface
 *  with zero thickness will appear black when viewed from behind
 *  unless backface visibility is off.
 *      The diffuse arguments are added to components in the BSDF file,
 *  not multiplied.  However, patterns affect this material as a multiplier
 *  on everything except non-diffuse reflection.
 *
 *  Arguments for MAT_BSDF are:
 *      6+      thick   BSDFfile        ux uy uz        funcfile        transform
 *      0
 *      0|3|6|9 rdf     gdf     bdf
 *              rdb     gdb     bdb
 *              rdt     gdt     bdt
 */

/*
 * Note that our reverse ray-tracing process means that the positions
 * of incoming and outgoing vectors may be reversed in our calls
 * to the BSDF library.  This is fine, since the bidirectional nature
 * of the BSDF (that's what the 'B' stands for) means it all works out.
 */

typedef struct {
        OBJREC  *mp;            /* material pointer */
        RAY     *pr;            /* intersected ray */
        FVECT   pnorm;          /* perturbed surface normal */
        FVECT   vray;           /* local outgoing (return) vector */
        double  sr_vpsa[2];     /* sqrt of BSDF projected solid angle extrema */
        RREAL   toloc[3][3];    /* world to local BSDF coords */
        RREAL   fromloc[3][3];  /* local BSDF coords to world */
        double  thick;          /* surface thickness */
        SDData  *sd;            /* loaded BSDF data */
        COLOR   runsamp;        /* BSDF hemispherical reflection */
        COLOR   rdiff;          /* added diffuse reflection */
        COLOR   tunsamp;        /* BSDF hemispherical transmission */
        COLOR   tdiff;          /* added diffuse transmission */
}  BSDFDAT;             /* BSDF material data */

#define cvt_sdcolor(cv, svp)    ccy2rgb(&(svp)->spec, (svp)->cieY, cv)

/* Jitter ray sample according to projected solid angle and specjitter */
static void
bsdf_jitter(FVECT vres, BSDFDAT *ndp, double sr_psa)
{
        VCOPY(vres, ndp->vray);
        if (specjitter < 1.)
                sr_psa *= specjitter;
        if (sr_psa <= FTINY)
                return;
        vres[0] += sr_psa*(.5 - frandom());
        vres[1] += sr_psa*(.5 - frandom());
        normalize(vres);
}

/* Evaluate BSDF for direct component, returning true if OK to proceed */
static int
direct_bsdf_OK(COLOR cval, FVECT ldir, double omega, BSDFDAT *ndp)
{
        int     nsamp, ok = 0;
        FVECT   vsrc, vsmp, vjit;
        double  tomega;
        double  sf, tsr, sd[2];
        COLOR   csmp;
        SDValue sv;
        SDError ec;
        int     i;
                                        /* transform source direction */
        if (SDmapDir(vsrc, ndp->toloc, ldir) != SDEnone)
                return(0);
                                        /* assign number of samples */
        ec = SDsizeBSDF(&tomega, ndp->vray, vsrc, SDqueryMin, ndp->sd);
        if (ec)
                goto baderror;
                                        /* check indirect over-counting */
        if (ndp->thick != 0 && ndp->pr->crtype & (SPECULAR|AMBIENT)
                                && vsrc[2] > 0 ^ ndp->vray[2] > 0) {
                double  dx = vsrc[0] + ndp->vray[0];
                double  dy = vsrc[1] + ndp->vray[1];
                if (dx*dx + dy*dy <= omega+tomega)
                        return(0);
        }
        sf = specjitter * ndp->pr->rweight;
        if (tomega <= .0)
                nsamp = 1;
        else if (25.*tomega <= omega)
                nsamp = 100.*sf + .5;
        else
                nsamp = 4.*sf*omega/tomega + .5;
        nsamp += !nsamp;
        setcolor(cval, .0, .0, .0);     /* sample our source area */
        sf = sqrt(omega);
        tsr = sqrt(tomega);
        for (i = nsamp; i--; ) {
                VCOPY(vsmp, vsrc);      /* jitter query directions */
                if (nsamp > 1) {
                        multisamp(sd, 2, (i + frandom())/(double)nsamp);
                        vsmp[0] += (sd[0] - .5)*sf;
                        vsmp[1] += (sd[1] - .5)*sf;
                        if (normalize(vsmp) == 0) {
                                --nsamp;
                                continue;
                        }
                }
                bsdf_jitter(vjit, ndp, tsr);
                                        /* compute BSDF */
                ec = SDevalBSDF(&sv, vjit, vsmp, ndp->sd);
                if (ec)
                        goto baderror;
                if (sv.cieY <= FTINY)   /* worth using? */
                        continue;
                cvt_sdcolor(csmp, &sv);
                addcolor(cval, csmp);   /* average it in */
                ++ok;
        }
        sf = 1./(double)nsamp;
        scalecolor(cval, sf);
        return(ok);
baderror:
        objerror(ndp->mp, USER, transSDError(ec));
        return(0);                      /* gratis return */
}

/* Compute source contribution for BSDF (reflected & transmitted) */
static void
dir_bsdf(
        COLOR  cval,                    /* returned coefficient */
        void  *nnp,                     /* material data */
        FVECT  ldir,                    /* light source direction */
        double  omega                   /* light source size */
)
{
        BSDFDAT         *np = (BSDFDAT *)nnp;
        double          ldot;
        double          dtmp;
        COLOR           ctmp;

        setcolor(cval, .0, .0, .0);

        ldot = DOT(np->pnorm, ldir);
        if ((-FTINY <= ldot) & (ldot <= FTINY))
                return;

        if (ldot > 0 && bright(np->rdiff) > FTINY) {
                /*
                 *  Compute added diffuse reflected component.
                 */
                copycolor(ctmp, np->rdiff);
                dtmp = ldot * omega * (1./PI);
                scalecolor(ctmp, dtmp);
                addcolor(cval, ctmp);
        }
        if (ldot < 0 && bright(np->tdiff) > FTINY) {
                /*
                 *  Compute added diffuse transmission.
                 */
                copycolor(ctmp, np->tdiff);
                dtmp = -ldot * omega * (1.0/PI);
                scalecolor(ctmp, dtmp);
                addcolor(cval, ctmp);
        }
        /*
         *  Compute scattering coefficient using BSDF.
         */
        if (!direct_bsdf_OK(ctmp, ldir, omega, np))
                return;
        if (ldot > 0) {         /* pattern only diffuse reflection */
                COLOR   ctmp1, ctmp2;
                dtmp = (np->pr->rod > 0) ? np->sd->rLambFront.cieY
                                        : np->sd->rLambBack.cieY;
                                        /* diffuse fraction */
                dtmp /= PI * bright(ctmp);
                copycolor(ctmp2, np->pr->pcol);
                scalecolor(ctmp2, dtmp);
                setcolor(ctmp1, 1.-dtmp, 1.-dtmp, 1.-dtmp);
                addcolor(ctmp1, ctmp2);
                multcolor(ctmp, ctmp1); /* apply derated pattern */
                dtmp = ldot * omega;
        } else {                        /* full pattern on transmission */
                multcolor(ctmp, np->pr->pcol);
                dtmp = -ldot * omega;
        }
        scalecolor(ctmp, dtmp);
        addcolor(cval, ctmp);
}

/* Compute source contribution for BSDF (reflected only) */
static void
dir_brdf(
        COLOR  cval,                    /* returned coefficient */
        void  *nnp,                     /* material data */
        FVECT  ldir,                    /* light source direction */
        double  omega                   /* light source size */
)
{
        BSDFDAT         *np = (BSDFDAT *)nnp;
        double          ldot;
        double          dtmp;
        COLOR           ctmp, ctmp1, ctmp2;

        setcolor(cval, .0, .0, .0);

        ldot = DOT(np->pnorm, ldir);
        
        if (ldot <= FTINY)
                return;

        if (bright(np->rdiff) > FTINY) {
                /*
                 *  Compute added diffuse reflected component.
                 */
                copycolor(ctmp, np->rdiff);
                dtmp = ldot * omega * (1./PI);
                scalecolor(ctmp, dtmp);
                addcolor(cval, ctmp);
        }
        /*
         *  Compute reflection coefficient using BSDF.
         */
        if (!direct_bsdf_OK(ctmp, ldir, omega, np))
                return;
                                        /* pattern only diffuse reflection */
        dtmp = (np->pr->rod > 0) ? np->sd->rLambFront.cieY
                                : np->sd->rLambBack.cieY;
        dtmp /= PI * bright(ctmp);      /* diffuse fraction */
        copycolor(ctmp2, np->pr->pcol);
        scalecolor(ctmp2, dtmp);
        setcolor(ctmp1, 1.-dtmp, 1.-dtmp, 1.-dtmp);
        addcolor(ctmp1, ctmp2);
        multcolor(ctmp, ctmp1);         /* apply derated pattern */
        dtmp = ldot * omega;
        scalecolor(ctmp, dtmp);
        addcolor(cval, ctmp);
}

/* Compute source contribution for BSDF (transmitted only) */
static void
dir_btdf(
        COLOR  cval,                    /* returned coefficient */
        void  *nnp,                     /* material data */
        FVECT  ldir,                    /* light source direction */
        double  omega                   /* light source size */
)
{
        BSDFDAT         *np = (BSDFDAT *)nnp;
        double          ldot;
        double          dtmp;
        COLOR           ctmp;

        setcolor(cval, .0, .0, .0);

        ldot = DOT(np->pnorm, ldir);

        if (ldot >= -FTINY)
                return;

        if (bright(np->tdiff) > FTINY) {
                /*
                 *  Compute added diffuse transmission.
                 */
                copycolor(ctmp, np->tdiff);
                dtmp = -ldot * omega * (1.0/PI);
                scalecolor(ctmp, dtmp);
                addcolor(cval, ctmp);
        }
        /*
         *  Compute scattering coefficient using BSDF.
         */
        if (!direct_bsdf_OK(ctmp, ldir, omega, np))
                return;
                                        /* full pattern on transmission */
        multcolor(ctmp, np->pr->pcol);
        dtmp = -ldot * omega;
        scalecolor(ctmp, dtmp);
        addcolor(cval, ctmp);
}

/* Sample separate BSDF component */
static int
sample_sdcomp(BSDFDAT *ndp, SDComponent *dcp, int usepat)
{
        int     nstarget = 1;
        int     nsent;
        SDError ec;
        SDValue bsv;
        double  xrand;
        FVECT   vsmp;
        RAY     sr;
                                                /* multiple samples? */
        if (specjitter > 1.5) {
                nstarget = specjitter*ndp->pr->rweight + .5;
                nstarget += !nstarget;
        }
                                                /* run through our samples */
        for (nsent = 0; nsent < nstarget; nsent++) {
                if (nstarget == 1) {            /* stratify random variable */
                        xrand = urand(ilhash(dimlist,ndims)+samplendx);
                        if (specjitter < 1.)
                                xrand = .5 + specjitter*(xrand-.5);
                } else {
                        xrand = (nsent + frandom())/(double)nstarget;
                }
                SDerrorDetail[0] = '\0';        /* sample direction & coef. */
                bsdf_jitter(vsmp, ndp, ndp->sr_vpsa[0]);
                ec = SDsampComponent(&bsv, vsmp, xrand, dcp);
                if (ec)
                        objerror(ndp->mp, USER, transSDError(ec));
                if (bsv.cieY <= FTINY)          /* zero component? */
                        break;
                                                /* map vector to world */
                if (SDmapDir(sr.rdir, ndp->fromloc, vsmp) != SDEnone)
                        break;
                                                /* spawn a specular ray */
                if (nstarget > 1)
                        bsv.cieY /= (double)nstarget;
                cvt_sdcolor(sr.rcoef, &bsv);    /* use sample color */
                if (usepat)                     /* apply pattern? */
                        multcolor(sr.rcoef, ndp->pr->pcol);
                if (rayorigin(&sr, SPECULAR, ndp->pr, sr.rcoef) < 0) {
                        if (maxdepth > 0)
                                break;
                        continue;               /* Russian roulette victim */
                }
                                                /* need to offset origin? */
                if (ndp->thick != 0 && ndp->pr->rod > 0 ^ vsmp[2] > 0)
                        VSUM(sr.rorg, sr.rorg, ndp->pr->ron, -ndp->thick);
                rayvalue(&sr);                  /* send & evaluate sample */
                multcolor(sr.rcol, sr.rcoef);
                addcolor(ndp->pr->rcol, sr.rcol);
        }
        return(nsent);
}

/* Sample non-diffuse components of BSDF */
static int
sample_sdf(BSDFDAT *ndp, int sflags)
{
        int             n, ntotal = 0;
        SDSpectralDF    *dfp;
        COLORV          *unsc;

        if (sflags == SDsampSpT) {
                unsc = ndp->tunsamp;
                if (ndp->pr->rod > 0)
                        dfp = (ndp->sd->tf != NULL) ? ndp->sd->tf : ndp->sd->tb;
                else
                        dfp = (ndp->sd->tb != NULL) ? ndp->sd->tb : ndp->sd->tf;
                cvt_sdcolor(unsc, &ndp->sd->tLamb);
        } else /* sflags == SDsampSpR */ {
                unsc = ndp->runsamp;
                if (ndp->pr->rod > 0) {
                        dfp = ndp->sd->rf;
                        cvt_sdcolor(unsc, &ndp->sd->rLambFront);
                } else {
                        dfp = ndp->sd->rb;
                        cvt_sdcolor(unsc, &ndp->sd->rLambBack);
                }
        }
        multcolor(unsc, ndp->pr->pcol);
        if (dfp == NULL)                        /* no specular component? */
                return(0);
                                                /* below sampling threshold? */
        if (dfp->maxHemi <= specthresh+FTINY) {
                if (dfp->maxHemi > FTINY) {     /* XXX no color from BSDF */
                        FVECT   vjit;
                        double  d;
                        COLOR   ctmp;
                        bsdf_jitter(vjit, ndp, ndp->sr_vpsa[1]);
                        d = SDdirectHemi(vjit, sflags, ndp->sd);
                        if (sflags == SDsampSpT) {
                                copycolor(ctmp, ndp->pr->pcol);
                                scalecolor(ctmp, d);
                        } else                  /* no pattern on reflection */
                                setcolor(ctmp, d, d, d);
                        addcolor(unsc, ctmp);
                }
                return(0);
        }
                                                /* else need to sample */
        dimlist[ndims++] = (int)(size_t)ndp->mp;
        ndims++;
        for (n = dfp->ncomp; n--; ) {           /* loop over components */
                dimlist[ndims-1] = n + 9438;
                ntotal += sample_sdcomp(ndp, &dfp->comp[n], sflags==SDsampSpT);
        }
        ndims -= 2;
        return(ntotal);
}

/* Color a ray that hit a BSDF material */
int
m_bsdf(OBJREC *m, RAY *r)
{
        int     hitfront;
        COLOR   ctmp;
        SDError ec;
        FVECT   upvec, vtmp;
        MFUNC   *mf;
        BSDFDAT nd;
                                                /* check arguments */
        if ((m->oargs.nsargs < 6) | (m->oargs.nfargs > 9) |
                                (m->oargs.nfargs % 3))
                objerror(m, USER, "bad # arguments");
                                                /* record surface struck */
        hitfront = (r->rod > 0);
                                                /* load cal file */
        mf = getfunc(m, 5, 0x1d, 1);
        setfunc(m, r);
                                                /* get thickness */
        nd.thick = evalue(mf->ep[0]);
        if ((-FTINY <= nd.thick) & (nd.thick <= FTINY))
                nd.thick = .0;
                                                /* check shadow */
        if (r->crtype & SHADOW) {
                if (nd.thick != 0)
                        raytrans(r);            /* pass-through */
                return(1);                      /* or shadow */
        }
                                                /* check backface visibility */
        if (!hitfront & !backvis) {
                raytrans(r);
                return(1);
        }
                                                /* check other rays to pass */
        if (nd.thick != 0 && (!(r->crtype & (SPECULAR|AMBIENT)) ||
                                nd.thick > 0 ^ hitfront)) {
                raytrans(r);                    /* hide our proxy */
                return(1);
        }
                                                /* get BSDF data */
        nd.sd = loadBSDF(m->oargs.sarg[1]);
                                                /* diffuse reflectance */
        if (hitfront) {
                if (m->oargs.nfargs < 3)
                        setcolor(nd.rdiff, .0, .0, .0);
                else
                        setcolor(nd.rdiff, m->oargs.farg[0],
                                        m->oargs.farg[1],
                                        m->oargs.farg[2]);
        } else {
                if (m->oargs.nfargs < 6)
                        setcolor(nd.rdiff, .0, .0, .0);
                else
                        setcolor(nd.rdiff, m->oargs.farg[3],
                                        m->oargs.farg[4],
                                        m->oargs.farg[5]);
        }
                                                /* diffuse transmittance */
        if (m->oargs.nfargs < 9)
                setcolor(nd.tdiff, .0, .0, .0);
        else
                setcolor(nd.tdiff, m->oargs.farg[6],
                                m->oargs.farg[7],
                                m->oargs.farg[8]);
        nd.mp = m;
        nd.pr = r;
                                                /* get modifiers */
        raytexture(r, m->omod);
                                                /* modify diffuse values */
        multcolor(nd.rdiff, r->pcol);
        multcolor(nd.tdiff, r->pcol);
                                                /* get up vector */
        upvec[0] = evalue(mf->ep[1]);
        upvec[1] = evalue(mf->ep[2]);
        upvec[2] = evalue(mf->ep[3]);
                                                /* return to world coords */
        if (mf->fxp != &unitxf) {
                multv3(upvec, upvec, mf->fxp->xfm);
                nd.thick *= mf->fxp->sca;
        }
        if (r->rox != NULL) {
                multv3(upvec, upvec, r->rox->f.xfm);
                nd.thick *= r->rox->f.sca;
        }
        raynormal(nd.pnorm, r);
                                                /* compute local BSDF xform */
        ec = SDcompXform(nd.toloc, nd.pnorm, upvec);
        if (!ec) {
                nd.vray[0] = -r->rdir[0];
                nd.vray[1] = -r->rdir[1];
                nd.vray[2] = -r->rdir[2];
                ec = SDmapDir(nd.vray, nd.toloc, nd.vray);
        }
        if (!ec)
                ec = SDinvXform(nd.fromloc, nd.toloc);
        if (ec) {
                objerror(m, WARNING, "Illegal orientation vector");
                return(1);
        }
                                                /* determine BSDF resolution */
        ec = SDsizeBSDF(nd.sr_vpsa, nd.vray, NULL, SDqueryMin+SDqueryMax, nd.sd);
        if (ec)
                objerror(m, USER, transSDError(ec));

        nd.sr_vpsa[0] = sqrt(nd.sr_vpsa[0]);
        nd.sr_vpsa[1] = sqrt(nd.sr_vpsa[1]);
        if (!hitfront) {                        /* perturb normal towards hit */
                nd.pnorm[0] = -nd.pnorm[0];
                nd.pnorm[1] = -nd.pnorm[1];
                nd.pnorm[2] = -nd.pnorm[2];
        }
                                                /* sample reflection */
        sample_sdf(&nd, SDsampSpR);
                                                /* sample transmission */
        sample_sdf(&nd, SDsampSpT);
                                                /* compute indirect diffuse */
        copycolor(ctmp, nd.rdiff);
        addcolor(ctmp, nd.runsamp);
        if (bright(ctmp) > FTINY) {             /* ambient from reflection */
                if (!hitfront)
                        flipsurface(r);
                multambient(ctmp, r, nd.pnorm);
                addcolor(r->rcol, ctmp);
                if (!hitfront)
                        flipsurface(r);
        }
        copycolor(ctmp, nd.tdiff);
        addcolor(ctmp, nd.tunsamp);
        if (bright(ctmp) > FTINY) {             /* ambient from other side */
                FVECT  bnorm;
                if (hitfront)
                        flipsurface(r);
                bnorm[0] = -nd.pnorm[0];
                bnorm[1] = -nd.pnorm[1];
                bnorm[2] = -nd.pnorm[2];
                if (nd.thick != 0) {            /* proxy with offset? */
                        VCOPY(vtmp, r->rop);
                        VSUM(r->rop, vtmp, r->ron, nd.thick);
                        multambient(ctmp, r, bnorm);
                        VCOPY(r->rop, vtmp);
                } else
                        multambient(ctmp, r, bnorm);
                addcolor(r->rcol, ctmp);
                if (hitfront)
                        flipsurface(r);
        }
                                                /* add direct component */
        if ((bright(nd.tdiff) <= FTINY) & (nd.sd->tf == NULL) &
                                        (nd.sd->tb == NULL)) {
                direct(r, dir_brdf, &nd);       /* reflection only */
        } else if (nd.thick == 0) {
                direct(r, dir_bsdf, &nd);       /* thin surface scattering */
        } else {
                direct(r, dir_brdf, &nd);       /* reflection first */
                VCOPY(vtmp, r->rop);            /* offset for transmitted */
                VSUM(r->rop, vtmp, r->ron, -nd.thick);
                direct(r, dir_btdf, &nd);       /* separate transmission */
                VCOPY(r->rop, vtmp);
        }
                                                /* clean up */
        SDfreeCache(nd.sd);
        return(1);
}
Revision:	2.26
Committed:	Sat Jan 25 18:27:39 2014 UTC (11 years, 9 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad4R2, rad4R2P1, rad4R2P2
Changes since 2.25:	+8 -9 lines
Log Message:	Enabled back face invisibility (-bv0) for transparent/translucent types
#	User	Rev	Content
1	greg	2.1	#ifndef lint
2	greg	2.26	static const char RCSid[] = "$Id: m_bsdf.c,v 2.25 2014/01/22 16:39:57 greg Exp $";
3	greg	2.1	#endif
4			/*
5			* Shading for materials with BSDFs taken from XML data files
6			*/
7
8			#include "copyright.h"
9
10			#include "ray.h"
11			#include "ambient.h"
12			#include "source.h"
13			#include "func.h"
14			#include "bsdf.h"
15			#include "random.h"
16
17			/*
18			* Arguments to this material include optional diffuse colors.
19			* String arguments include the BSDF and function files.
20	greg	2.5	* A non-zero thickness causes the strange but useful behavior
21			* of translating transmitted rays this distance beneath the surface
22			* (opposite the surface normal) to bypass any intervening geometry.
23			* Translation only affects scattered, non-source-directed samples.
24			* A non-zero thickness has the further side-effect that an unscattered
25	greg	2.1	* (view) ray will pass right through our material if it has any
26	greg	2.5	* non-diffuse transmission, making the BSDF surface invisible. This
27			* shows the proxied geometry instead. Thickness has the further
28			* effect of turning off reflection on the hidden side so that rays
29			* heading in the opposite direction pass unimpeded through the BSDF
30			* surface. A paired surface may be placed on the opposide side of
31			* the detail geometry, less than this thickness away, if a two-way
32			* proxy is desired. Note that the sign of the thickness is important.
33			* A positive thickness hides geometry behind the BSDF surface and uses
34			* front reflectance and transmission properties. A negative thickness
35			* hides geometry in front of the surface when rays hit from behind,
36			* and applies only the transmission and backside reflectance properties.
37			* Reflection is ignored on the hidden side, as those rays pass through.
38	greg	2.1	* The "up" vector for the BSDF is given by three variables, defined
39			* (along with the thickness) by the named function file, or '.' if none.
40			* Together with the surface normal, this defines the local coordinate
41			* system for the BSDF.
42			* We do not reorient the surface, so if the BSDF has no back-side
43	greg	2.5	* reflectance and none is given in the real arguments, a BSDF surface
44			* with zero thickness will appear black when viewed from behind
45			* unless backface visibility is off.
46			* The diffuse arguments are added to components in the BSDF file,
47	greg	2.1	* not multiplied. However, patterns affect this material as a multiplier
48			* on everything except non-diffuse reflection.
49			*
50			* Arguments for MAT_BSDF are:
51			* 6+ thick BSDFfile ux uy uz funcfile transform
52			* 0
53	greg	2.8	* 0\|3\|6\|9 rdf gdf bdf
54	greg	2.1	* rdb gdb bdb
55			* rdt gdt bdt
56			*/
57
58	greg	2.4	/*
59			* Note that our reverse ray-tracing process means that the positions
60			* of incoming and outgoing vectors may be reversed in our calls
61			* to the BSDF library. This is fine, since the bidirectional nature
62			* of the BSDF (that's what the 'B' stands for) means it all works out.
63			*/
64
65	greg	2.1	typedef struct {
66			OBJREC mp; / material pointer */
67			RAY pr; / intersected ray */
68			FVECT pnorm; /* perturbed surface normal */
69	greg	2.4	FVECT vray; /* local outgoing (return) vector */
70	greg	2.9	double sr_vpsa[2]; /* sqrt of BSDF projected solid angle extrema */
71	greg	2.1	RREAL toloc[3][3]; /* world to local BSDF coords */
72			RREAL fromloc[3][3]; /* local BSDF coords to world */
73			double thick; /* surface thickness */
74			SDData sd; / loaded BSDF data */
75			COLOR runsamp; /* BSDF hemispherical reflection */
76			COLOR rdiff; /* added diffuse reflection */
77			COLOR tunsamp; /* BSDF hemispherical transmission */
78			COLOR tdiff; /* added diffuse transmission */
79			} BSDFDAT; /* BSDF material data */
80
81			#define cvt_sdcolor(cv, svp) ccy2rgb(&(svp)->spec, (svp)->cieY, cv)
82
83	greg	2.4	/* Jitter ray sample according to projected solid angle and specjitter */
84			static void
85	greg	2.15	bsdf_jitter(FVECT vres, BSDFDAT *ndp, double sr_psa)
86	greg	2.4	{
87			VCOPY(vres, ndp->vray);
88			if (specjitter < 1.)
89			sr_psa *= specjitter;
90			if (sr_psa <= FTINY)
91			return;
92			vres[0] += sr_psa*(.5 - frandom());
93			vres[1] += sr_psa*(.5 - frandom());
94			normalize(vres);
95			}
96
97	greg	2.7	/* Evaluate BSDF for direct component, returning true if OK to proceed */
98			static int
99	greg	2.13	direct_bsdf_OK(COLOR cval, FVECT ldir, double omega, BSDFDAT *ndp)
100	greg	2.7	{
101	greg	2.15	int nsamp, ok = 0;
102	greg	2.13	FVECT vsrc, vsmp, vjit;
103			double tomega;
104	greg	2.15	double sf, tsr, sd[2];
105	greg	2.13	COLOR csmp;
106	greg	2.7	SDValue sv;
107			SDError ec;
108	greg	2.13	int i;
109	greg	2.7	/* transform source direction */
110			if (SDmapDir(vsrc, ndp->toloc, ldir) != SDEnone)
111			return(0);
112	greg	2.16	/* assign number of samples */
113			ec = SDsizeBSDF(&tomega, ndp->vray, vsrc, SDqueryMin, ndp->sd);
114			if (ec)
115			goto baderror;
116	greg	2.13	/* check indirect over-counting */
117			if (ndp->thick != 0 && ndp->pr->crtype & (SPECULAR\|AMBIENT)
118			&& vsrc[2] > 0 ^ ndp->vray[2] > 0) {
119			double dx = vsrc[0] + ndp->vray[0];
120			double dy = vsrc[1] + ndp->vray[1];
121	greg	2.16	if (dxdx + dydy <= omega+tomega)
122	greg	2.7	return(0);
123			}
124	greg	2.15	sf = specjitter * ndp->pr->rweight;
125	greg	2.24	if (tomega <= .0)
126			nsamp = 1;
127			else if (25.*tomega <= omega)
128	greg	2.15	nsamp = 100.*sf + .5;
129			else
130			nsamp = 4.sfomega/tomega + .5;
131			nsamp += !nsamp;
132			setcolor(cval, .0, .0, .0); /* sample our source area */
133	greg	2.13	sf = sqrt(omega);
134	greg	2.15	tsr = sqrt(tomega);
135	greg	2.13	for (i = nsamp; i--; ) {
136			VCOPY(vsmp, vsrc); /* jitter query directions */
137			if (nsamp > 1) {
138			multisamp(sd, 2, (i + frandom())/(double)nsamp);
139			vsmp[0] += (sd[0] - .5)*sf;
140			vsmp[1] += (sd[1] - .5)*sf;
141			if (normalize(vsmp) == 0) {
142			--nsamp;
143			continue;
144			}
145			}
146	greg	2.15	bsdf_jitter(vjit, ndp, tsr);
147	greg	2.13	/* compute BSDF */
148			ec = SDevalBSDF(&sv, vjit, vsmp, ndp->sd);
149			if (ec)
150			goto baderror;
151			if (sv.cieY <= FTINY) /* worth using? */
152			continue;
153			cvt_sdcolor(csmp, &sv);
154			addcolor(cval, csmp); /* average it in */
155			++ok;
156			}
157			sf = 1./(double)nsamp;
158			scalecolor(cval, sf);
159			return(ok);
160			baderror:
161			objerror(ndp->mp, USER, transSDError(ec));
162	greg	2.17	return(0); /* gratis return */
163	greg	2.7	}
164
165	greg	2.5	/* Compute source contribution for BSDF (reflected & transmitted) */
166	greg	2.1	static void
167	greg	2.5	dir_bsdf(
168	greg	2.1	COLOR cval, /* returned coefficient */
169			void nnp, / material data */
170			FVECT ldir, /* light source direction */
171			double omega /* light source size */
172			)
173			{
174	greg	2.3	BSDFDAT np = (BSDFDAT )nnp;
175	greg	2.1	double ldot;
176			double dtmp;
177			COLOR ctmp;
178
179			setcolor(cval, .0, .0, .0);
180
181			ldot = DOT(np->pnorm, ldir);
182			if ((-FTINY <= ldot) & (ldot <= FTINY))
183			return;
184
185	greg	2.9	if (ldot > 0 && bright(np->rdiff) > FTINY) {
186	greg	2.1	/*
187			* Compute added diffuse reflected component.
188			*/
189			copycolor(ctmp, np->rdiff);
190			dtmp = ldot * omega * (1./PI);
191			scalecolor(ctmp, dtmp);
192			addcolor(cval, ctmp);
193			}
194	greg	2.9	if (ldot < 0 && bright(np->tdiff) > FTINY) {
195	greg	2.1	/*
196			* Compute added diffuse transmission.
197			*/
198			copycolor(ctmp, np->tdiff);
199			dtmp = -ldot * omega * (1.0/PI);
200			scalecolor(ctmp, dtmp);
201			addcolor(cval, ctmp);
202			}
203			/*
204			* Compute scattering coefficient using BSDF.
205			*/
206	greg	2.13	if (!direct_bsdf_OK(ctmp, ldir, omega, np))
207	greg	2.1	return;
208	greg	2.9	if (ldot > 0) { /* pattern only diffuse reflection */
209	greg	2.1	COLOR ctmp1, ctmp2;
210	greg	2.9	dtmp = (np->pr->rod > 0) ? np->sd->rLambFront.cieY
211	greg	2.1	: np->sd->rLambBack.cieY;
212	greg	2.7	/* diffuse fraction */
213			dtmp /= PI * bright(ctmp);
214	greg	2.1	copycolor(ctmp2, np->pr->pcol);
215			scalecolor(ctmp2, dtmp);
216			setcolor(ctmp1, 1.-dtmp, 1.-dtmp, 1.-dtmp);
217			addcolor(ctmp1, ctmp2);
218	greg	2.3	multcolor(ctmp, ctmp1); /* apply derated pattern */
219	greg	2.1	dtmp = ldot * omega;
220			} else { /* full pattern on transmission */
221			multcolor(ctmp, np->pr->pcol);
222			dtmp = -ldot * omega;
223			}
224			scalecolor(ctmp, dtmp);
225			addcolor(cval, ctmp);
226			}
227
228	greg	2.5	/* Compute source contribution for BSDF (reflected only) */
229			static void
230			dir_brdf(
231			COLOR cval, /* returned coefficient */
232			void nnp, / material data */
233			FVECT ldir, /* light source direction */
234			double omega /* light source size */
235			)
236			{
237			BSDFDAT np = (BSDFDAT )nnp;
238			double ldot;
239			double dtmp;
240			COLOR ctmp, ctmp1, ctmp2;
241
242			setcolor(cval, .0, .0, .0);
243
244			ldot = DOT(np->pnorm, ldir);
245
246			if (ldot <= FTINY)
247			return;
248
249			if (bright(np->rdiff) > FTINY) {
250			/*
251			* Compute added diffuse reflected component.
252			*/
253			copycolor(ctmp, np->rdiff);
254			dtmp = ldot * omega * (1./PI);
255			scalecolor(ctmp, dtmp);
256			addcolor(cval, ctmp);
257			}
258			/*
259			* Compute reflection coefficient using BSDF.
260			*/
261	greg	2.13	if (!direct_bsdf_OK(ctmp, ldir, omega, np))
262	greg	2.5	return;
263			/* pattern only diffuse reflection */
264	greg	2.9	dtmp = (np->pr->rod > 0) ? np->sd->rLambFront.cieY
265	greg	2.5	: np->sd->rLambBack.cieY;
266	greg	2.7	dtmp /= PI * bright(ctmp); /* diffuse fraction */
267	greg	2.5	copycolor(ctmp2, np->pr->pcol);
268			scalecolor(ctmp2, dtmp);
269			setcolor(ctmp1, 1.-dtmp, 1.-dtmp, 1.-dtmp);
270			addcolor(ctmp1, ctmp2);
271			multcolor(ctmp, ctmp1); /* apply derated pattern */
272			dtmp = ldot * omega;
273			scalecolor(ctmp, dtmp);
274			addcolor(cval, ctmp);
275			}
276
277			/* Compute source contribution for BSDF (transmitted only) */
278			static void
279			dir_btdf(
280			COLOR cval, /* returned coefficient */
281			void nnp, / material data */
282			FVECT ldir, /* light source direction */
283			double omega /* light source size */
284			)
285			{
286			BSDFDAT np = (BSDFDAT )nnp;
287			double ldot;
288			double dtmp;
289			COLOR ctmp;
290
291			setcolor(cval, .0, .0, .0);
292
293			ldot = DOT(np->pnorm, ldir);
294
295			if (ldot >= -FTINY)
296			return;
297
298			if (bright(np->tdiff) > FTINY) {
299			/*
300			* Compute added diffuse transmission.
301			*/
302			copycolor(ctmp, np->tdiff);
303			dtmp = -ldot * omega * (1.0/PI);
304			scalecolor(ctmp, dtmp);
305			addcolor(cval, ctmp);
306			}
307			/*
308			* Compute scattering coefficient using BSDF.
309			*/
310	greg	2.13	if (!direct_bsdf_OK(ctmp, ldir, omega, np))
311	greg	2.5	return;
312			/* full pattern on transmission */
313			multcolor(ctmp, np->pr->pcol);
314			dtmp = -ldot * omega;
315			scalecolor(ctmp, dtmp);
316			addcolor(cval, ctmp);
317			}
318
319	greg	2.1	/* Sample separate BSDF component */
320			static int
321			sample_sdcomp(BSDFDAT ndp, SDComponent dcp, int usepat)
322			{
323			int nstarget = 1;
324	greg	2.11	int nsent;
325	greg	2.1	SDError ec;
326			SDValue bsv;
327	greg	2.11	double xrand;
328	greg	2.10	FVECT vsmp;
329	greg	2.1	RAY sr;
330			/* multiple samples? */
331			if (specjitter > 1.5) {
332			nstarget = specjitter*ndp->pr->rweight + .5;
333	greg	2.14	nstarget += !nstarget;
334	greg	2.1	}
335	greg	2.11	/* run through our samples */
336			for (nsent = 0; nsent < nstarget; nsent++) {
337	greg	2.15	if (nstarget == 1) { /* stratify random variable */
338	greg	2.11	xrand = urand(ilhash(dimlist,ndims)+samplendx);
339	greg	2.15	if (specjitter < 1.)
340			xrand = .5 + specjitter*(xrand-.5);
341			} else {
342	greg	2.11	xrand = (nsent + frandom())/(double)nstarget;
343	greg	2.15	}
344	greg	2.11	SDerrorDetail[0] = '\0'; /* sample direction & coef. */
345	greg	2.15	bsdf_jitter(vsmp, ndp, ndp->sr_vpsa[0]);
346	greg	2.11	ec = SDsampComponent(&bsv, vsmp, xrand, dcp);
347	greg	2.1	if (ec)
348	greg	2.2	objerror(ndp->mp, USER, transSDError(ec));
349	greg	2.11	if (bsv.cieY <= FTINY) /* zero component? */
350	greg	2.1	break;
351			/* map vector to world */
352	greg	2.4	if (SDmapDir(sr.rdir, ndp->fromloc, vsmp) != SDEnone)
353	greg	2.1	break;
354			/* spawn a specular ray */
355			if (nstarget > 1)
356			bsv.cieY /= (double)nstarget;
357	greg	2.11	cvt_sdcolor(sr.rcoef, &bsv); /* use sample color */
358			if (usepat) /* apply pattern? */
359	greg	2.1	multcolor(sr.rcoef, ndp->pr->pcol);
360			if (rayorigin(&sr, SPECULAR, ndp->pr, sr.rcoef) < 0) {
361	greg	2.11	if (maxdepth > 0)
362	greg	2.1	break;
363	greg	2.11	continue; /* Russian roulette victim */
364	greg	2.1	}
365	greg	2.5	/* need to offset origin? */
366	greg	2.9	if (ndp->thick != 0 && ndp->pr->rod > 0 ^ vsmp[2] > 0)
367	greg	2.5	VSUM(sr.rorg, sr.rorg, ndp->pr->ron, -ndp->thick);
368	greg	2.1	rayvalue(&sr); /* send & evaluate sample */
369			multcolor(sr.rcol, sr.rcoef);
370			addcolor(ndp->pr->rcol, sr.rcol);
371			}
372			return(nsent);
373			}
374
375			/* Sample non-diffuse components of BSDF */
376			static int
377			sample_sdf(BSDFDAT *ndp, int sflags)
378			{
379			int n, ntotal = 0;
380			SDSpectralDF *dfp;
381			COLORV *unsc;
382
383			if (sflags == SDsampSpT) {
384			unsc = ndp->tunsamp;
385	greg	2.22	if (ndp->pr->rod > 0)
386			dfp = (ndp->sd->tf != NULL) ? ndp->sd->tf : ndp->sd->tb;
387			else
388			dfp = (ndp->sd->tb != NULL) ? ndp->sd->tb : ndp->sd->tf;
389	greg	2.1	cvt_sdcolor(unsc, &ndp->sd->tLamb);
390			} else /* sflags == SDsampSpR */ {
391			unsc = ndp->runsamp;
392	greg	2.9	if (ndp->pr->rod > 0) {
393	greg	2.1	dfp = ndp->sd->rf;
394			cvt_sdcolor(unsc, &ndp->sd->rLambFront);
395			} else {
396			dfp = ndp->sd->rb;
397			cvt_sdcolor(unsc, &ndp->sd->rLambBack);
398			}
399			}
400			multcolor(unsc, ndp->pr->pcol);
401			if (dfp == NULL) /* no specular component? */
402			return(0);
403			/* below sampling threshold? */
404			if (dfp->maxHemi <= specthresh+FTINY) {
405	greg	2.3	if (dfp->maxHemi > FTINY) { /* XXX no color from BSDF */
406	greg	2.4	FVECT vjit;
407			double d;
408	greg	2.1	COLOR ctmp;
409	greg	2.15	bsdf_jitter(vjit, ndp, ndp->sr_vpsa[1]);
410	greg	2.4	d = SDdirectHemi(vjit, sflags, ndp->sd);
411	greg	2.1	if (sflags == SDsampSpT) {
412			copycolor(ctmp, ndp->pr->pcol);
413			scalecolor(ctmp, d);
414			} else /* no pattern on reflection */
415			setcolor(ctmp, d, d, d);
416			addcolor(unsc, ctmp);
417			}
418			return(0);
419			}
420			/* else need to sample */
421			dimlist[ndims++] = (int)(size_t)ndp->mp;
422			ndims++;
423			for (n = dfp->ncomp; n--; ) { /* loop over components */
424			dimlist[ndims-1] = n + 9438;
425			ntotal += sample_sdcomp(ndp, &dfp->comp[n], sflags==SDsampSpT);
426			}
427			ndims -= 2;
428			return(ntotal);
429			}
430
431			/* Color a ray that hit a BSDF material */
432			int
433			m_bsdf(OBJREC m, RAY r)
434			{
435	greg	2.6	int hitfront;
436	greg	2.1	COLOR ctmp;
437			SDError ec;
438	greg	2.5	FVECT upvec, vtmp;
439	greg	2.1	MFUNC *mf;
440			BSDFDAT nd;
441			/* check arguments */
442			if ((m->oargs.nsargs < 6) \| (m->oargs.nfargs > 9) \|
443			(m->oargs.nfargs % 3))
444			objerror(m, USER, "bad # arguments");
445	greg	2.6	/* record surface struck */
446	greg	2.9	hitfront = (r->rod > 0);
447	greg	2.1	/* load cal file */
448			mf = getfunc(m, 5, 0x1d, 1);
449	greg	2.25	setfunc(m, r);
450	greg	2.1	/* get thickness */
451			nd.thick = evalue(mf->ep[0]);
452	greg	2.5	if ((-FTINY <= nd.thick) & (nd.thick <= FTINY))
453	greg	2.1	nd.thick = .0;
454			/* check shadow */
455			if (r->crtype & SHADOW) {
456	greg	2.9	if (nd.thick != 0)
457	greg	2.3	raytrans(r); /* pass-through */
458	greg	2.5	return(1); /* or shadow */
459	greg	2.1	}
460	greg	2.26	/* check backface visibility */
461			if (!hitfront & !backvis) {
462			raytrans(r);
463			return(1);
464			}
465	greg	2.5	/* check other rays to pass */
466	greg	2.9	if (nd.thick != 0 && (!(r->crtype & (SPECULAR\|AMBIENT)) \|\|
467			nd.thick > 0 ^ hitfront)) {
468	greg	2.5	raytrans(r); /* hide our proxy */
469	greg	2.1	return(1);
470			}
471	greg	2.5	/* get BSDF data */
472			nd.sd = loadBSDF(m->oargs.sarg[1]);
473	greg	2.1	/* diffuse reflectance */
474	greg	2.6	if (hitfront) {
475	greg	2.1	if (m->oargs.nfargs < 3)
476			setcolor(nd.rdiff, .0, .0, .0);
477			else
478			setcolor(nd.rdiff, m->oargs.farg[0],
479			m->oargs.farg[1],
480			m->oargs.farg[2]);
481			} else {
482	greg	2.26	if (m->oargs.nfargs < 6)
483	greg	2.1	setcolor(nd.rdiff, .0, .0, .0);
484	greg	2.26	else
485	greg	2.1	setcolor(nd.rdiff, m->oargs.farg[3],
486			m->oargs.farg[4],
487			m->oargs.farg[5]);
488			}
489			/* diffuse transmittance */
490			if (m->oargs.nfargs < 9)
491			setcolor(nd.tdiff, .0, .0, .0);
492			else
493			setcolor(nd.tdiff, m->oargs.farg[6],
494			m->oargs.farg[7],
495			m->oargs.farg[8]);
496			nd.mp = m;
497			nd.pr = r;
498			/* get modifiers */
499			raytexture(r, m->omod);
500			/* modify diffuse values */
501			multcolor(nd.rdiff, r->pcol);
502			multcolor(nd.tdiff, r->pcol);
503			/* get up vector */
504			upvec[0] = evalue(mf->ep[1]);
505			upvec[1] = evalue(mf->ep[2]);
506			upvec[2] = evalue(mf->ep[3]);
507			/* return to world coords */
508	greg	2.21	if (mf->fxp != &unitxf) {
509			multv3(upvec, upvec, mf->fxp->xfm);
510			nd.thick *= mf->fxp->sca;
511	greg	2.1	}
512	greg	2.23	if (r->rox != NULL) {
513			multv3(upvec, upvec, r->rox->f.xfm);
514			nd.thick *= r->rox->f.sca;
515			}
516	greg	2.1	raynormal(nd.pnorm, r);
517			/* compute local BSDF xform */
518			ec = SDcompXform(nd.toloc, nd.pnorm, upvec);
519			if (!ec) {
520	greg	2.4	nd.vray[0] = -r->rdir[0];
521			nd.vray[1] = -r->rdir[1];
522			nd.vray[2] = -r->rdir[2];
523			ec = SDmapDir(nd.vray, nd.toloc, nd.vray);
524	greg	2.20	}
525			if (!ec)
526			ec = SDinvXform(nd.fromloc, nd.toloc);
527	greg	2.19	if (ec) {
528			objerror(m, WARNING, "Illegal orientation vector");
529			return(1);
530	greg	2.1	}
531	greg	2.4	/* determine BSDF resolution */
532	greg	2.20	ec = SDsizeBSDF(nd.sr_vpsa, nd.vray, NULL, SDqueryMin+SDqueryMax, nd.sd);
533			if (ec)
534			objerror(m, USER, transSDError(ec));
535
536	greg	2.9	nd.sr_vpsa[0] = sqrt(nd.sr_vpsa[0]);
537			nd.sr_vpsa[1] = sqrt(nd.sr_vpsa[1]);
538	greg	2.6	if (!hitfront) { /* perturb normal towards hit */
539	greg	2.1	nd.pnorm[0] = -nd.pnorm[0];
540			nd.pnorm[1] = -nd.pnorm[1];
541			nd.pnorm[2] = -nd.pnorm[2];
542			}
543			/* sample reflection */
544			sample_sdf(&nd, SDsampSpR);
545			/* sample transmission */
546			sample_sdf(&nd, SDsampSpT);
547			/* compute indirect diffuse */
548			copycolor(ctmp, nd.rdiff);
549			addcolor(ctmp, nd.runsamp);
550	greg	2.5	if (bright(ctmp) > FTINY) { /* ambient from reflection */
551	greg	2.6	if (!hitfront)
552	greg	2.1	flipsurface(r);
553			multambient(ctmp, r, nd.pnorm);
554			addcolor(r->rcol, ctmp);
555	greg	2.6	if (!hitfront)
556	greg	2.1	flipsurface(r);
557			}
558			copycolor(ctmp, nd.tdiff);
559			addcolor(ctmp, nd.tunsamp);
560			if (bright(ctmp) > FTINY) { /* ambient from other side */
561			FVECT bnorm;
562	greg	2.6	if (hitfront)
563	greg	2.1	flipsurface(r);
564			bnorm[0] = -nd.pnorm[0];
565			bnorm[1] = -nd.pnorm[1];
566			bnorm[2] = -nd.pnorm[2];
567	greg	2.9	if (nd.thick != 0) { /* proxy with offset? */
568	greg	2.5	VCOPY(vtmp, r->rop);
569	greg	2.18	VSUM(r->rop, vtmp, r->ron, nd.thick);
570	greg	2.5	multambient(ctmp, r, bnorm);
571			VCOPY(r->rop, vtmp);
572			} else
573			multambient(ctmp, r, bnorm);
574	greg	2.1	addcolor(r->rcol, ctmp);
575	greg	2.6	if (hitfront)
576	greg	2.1	flipsurface(r);
577			}
578			/* add direct component */
579	greg	2.22	if ((bright(nd.tdiff) <= FTINY) & (nd.sd->tf == NULL) &
580			(nd.sd->tb == NULL)) {
581	greg	2.5	direct(r, dir_brdf, &nd); /* reflection only */
582	greg	2.9	} else if (nd.thick == 0) {
583	greg	2.5	direct(r, dir_bsdf, &nd); /* thin surface scattering */
584			} else {
585			direct(r, dir_brdf, &nd); /* reflection first */
586			VCOPY(vtmp, r->rop); /* offset for transmitted */
587			VSUM(r->rop, vtmp, r->ron, -nd.thick);
588	greg	2.6	direct(r, dir_btdf, &nd); /* separate transmission */
589	greg	2.5	VCOPY(r->rop, vtmp);
590			}
591	greg	2.1	/* clean up */
592			SDfreeCache(nd.sd);
593			return(1);
594			}