src/rt/m_bsdf.c

#ifndef lint
static const char RCSid[] = "$Id: m_bsdf.c,v 2.36 2017/05/16 20:06:40 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"
#include  "pmapmat.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, making the BSDF
 *  surface invisible and showing the proxied geometry instead. Thickness
 *  has the further effect of turning off reflection on the reverse side so
 *  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.
 *      When thickness is set to zero, shadow rays will be blocked unless
 *  a BTDF has a strong "through" component in the source direction.
 *  A separate test prevents over-counting by dropping specular & ambient
 *  samples that are too close to this "through" direction.  The same
 *  restriction applies for the proxy case (thickness != 0).
 *      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 on, when it becomes invisible.
 *      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 usually 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 */
        COLOR   cthru;          /* "through" component multiplier */
        SDData  *sd;            /* loaded BSDF data */
        COLOR   rdiff;          /* diffuse reflection */
        COLOR   tdiff;          /* diffuse transmission */
}  BSDFDAT;             /* BSDF material data */

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

/* Compute "through" component color */
static void
compute_through(BSDFDAT *ndp)
{
#define NDIR2CHECK      13
        static const float      dir2check[NDIR2CHECK][2] = {
                                        {0, 0},
                                        {-0.8, 0},
                                        {0, 0.8},
                                        {0, -0.8},
                                        {0.8, 0},
                                        {-0.8, 0.8},
                                        {-0.8, -0.8},
                                        {0.8, 0.8},
                                        {0.8, -0.8},
                                        {-1.6, 0},
                                        {0, 1.6},
                                        {0, -1.6},
                                        {1.6, 0},
                                };
        const double    peak_over = 2.0;
        SDSpectralDF    *dfp;
        FVECT           pdir;
        double          tomega, srchrad;
        COLOR           vpeak, vsum;
        int             nsum, i;
        SDError         ec;

        setcolor(ndp->cthru, .0, .0, .0);       /* starting assumption */

        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;

        if (dfp == NULL)
                return;                         /* no specular transmission */
        if (bright(ndp->pr->pcol) <= FTINY)
                return;                         /* pattern is black, here */
        srchrad = sqrt(dfp->minProjSA);         /* else search for peak */
        setcolor(vpeak, .0, .0, .0);
        setcolor(vsum, .0, .0, .0);
        nsum = 0;
        for (i = 0; i < NDIR2CHECK; i++) {
                FVECT   tdir;
                SDValue sv;
                COLOR   vcol;
                tdir[0] = -ndp->vray[0] + dir2check[i][0]*srchrad;
                tdir[1] = -ndp->vray[1] + dir2check[i][1]*srchrad;
                tdir[2] = -ndp->vray[2];
                normalize(tdir);
                ec = SDevalBSDF(&sv, tdir, ndp->vray, ndp->sd);
                if (ec)
                        goto baderror;
                cvt_sdcolor(vcol, &sv);
                addcolor(vsum, vcol);
                ++nsum;
                if (bright(vcol) > bright(vpeak)) {
                        copycolor(vpeak, vcol);
                        VCOPY(pdir, tdir);
                }
        }
        ec = SDsizeBSDF(&tomega, pdir, ndp->vray, SDqueryMin, ndp->sd);
        if (ec)
                goto baderror;
        if (tomega > 1.5*dfp->minProjSA)
                return;                         /* not really a peak? */
        if ((bright(vpeak) - ndp->sd->tLamb.cieY*(1./PI))*tomega <= .007)
                return;                         /* < 0.7% transmission */
        for (i = 3; i--; )                      /* remove peak from average */
                colval(vsum,i) -= colval(vpeak,i);
        --nsum;
        if (peak_over*bright(vsum) >= nsum*bright(vpeak))
                return;                         /* not peaky enough */
        copycolor(ndp->cthru, vpeak);           /* else use it */
        scalecolor(ndp->cthru, tomega);
        multcolor(ndp->cthru, ndp->pr->pcol);   /* modify by pattern */
        return;
baderror:
        objerror(ndp->mp, USER, transSDError(ec));
#undef NDIR2CHECK
}

/* 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);
}

/* Get BSDF specular for direct component, returning true if OK to proceed */
static int
direct_specular_OK(COLOR cval, FVECT ldir, double omega, BSDFDAT *ndp)
{
        int     nsamp, ok = 0;
        FVECT   vsrc, vsmp, vjit;
        double  tomega, tomega2;
        double  sf, tsr, sd[2];
        COLOR   csmp, cdiff;
        double  diffY;
        SDValue sv;
        SDError ec;
        int     i;
                                        /* in case we fail */
        setcolor(cval, .0, .0, .0);
                                        /* transform source direction */
        if (SDmapDir(vsrc, ndp->toloc, ldir) != SDEnone)
                return(0);
                                        /* will discount diffuse portion */
        switch ((vsrc[2] > 0)<<1 | (ndp->vray[2] > 0)) {
        case 3:
                if (ndp->sd->rf == NULL)
                        return(0);      /* all diffuse */
                sv = ndp->sd->rLambFront;
                break;
        case 0:
                if (ndp->sd->rb == NULL)
                        return(0);      /* all diffuse */
                sv = ndp->sd->rLambBack;
                break;
        default:
                if ((ndp->sd->tf == NULL) & (ndp->sd->tb == NULL))
                        return(0);      /* all diffuse */
                sv = ndp->sd->tLamb;
                break;
        }
        if (sv.cieY > FTINY) {
                diffY = sv.cieY *= 1./PI;
                cvt_sdcolor(cdiff, &sv);
        } else {
                diffY = .0;
                setcolor(cdiff, .0, .0, .0);
        }
                                        /* need projected solid angles */
        omega *= fabs(vsrc[2]);
        ec = SDsizeBSDF(&tomega, ndp->vray, vsrc, SDqueryMin, ndp->sd);
        if (ec)
                goto baderror;
                                        /* check indirect over-counting */
        if ((ndp->thick != 0 || bright(ndp->cthru) > FTINY)
                                && 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 <= (4./PI)*(omega + tomega +
                                                2.*sqrt(omega*tomega)))
                        return(0);
        }
                                        /* assign number of samples */
        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;
        sf = sqrt(omega);               /* sample our source area */
        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;
                        normalize(vsmp);
                }
                bsdf_jitter(vjit, ndp, tsr);
                                        /* compute BSDF */
                ec = SDevalBSDF(&sv, vjit, vsmp, ndp->sd);
                if (ec)
                        goto baderror;
                if (sv.cieY - diffY <= FTINY)
                        continue;       /* no specular part */
                                        /* check for variable resolution */
                ec = SDsizeBSDF(&tomega2, vjit, vsmp, SDqueryMin, ndp->sd);
                if (ec)
                        goto baderror;
                if (tomega2 < .12*tomega)
                        continue;       /* not safe to include */
                cvt_sdcolor(csmp, &sv);
                addcolor(cval, csmp);   /* else average it in */
                ++ok;
        }
        if (!ok)                        /* no valid specular samples? */
                return(0);

        sf = 1./(double)ok;             /* compute average BSDF */
        scalecolor(cval, sf);
                                        /* subtract diffuse contribution */
        for (i = 3*(diffY > FTINY); i--; )
                if ((colval(cval,i) -= colval(cdiff,i)) < .0)
                        colval(cval,i) = .0;
        return(1);
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);
        }
        if (ambRayInPmap(np->pr))
                return;         /* specular already in photon map */
        /*
         *  Compute specular scattering coefficient using BSDF.
         */
        if (!direct_specular_OK(ctmp, ldir, omega, np))
                return;
        if (ldot < 0) {         /* pattern for specular transmission */
                multcolor(ctmp, np->pr->pcol);
                dtmp = -ldot * omega;
        } else
                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);
        }
        if (ambRayInPmap(np->pr))
                return;         /* specular already in photon map */
        /*
         *  Compute specular reflection coefficient using BSDF.
         */
        if (!direct_specular_OK(ctmp, ldir, omega, np))
                return;
        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);
        }
        if (ambRayInPmap(np->pr))
                return;         /* specular already in photon map */
        /*
         *  Compute specular scattering coefficient using BSDF.
         */
        if (!direct_specular_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->tdiff;
                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;
        } else /* sflags == SDsampSpR */ {
                unsc = ndp->rdiff;
                if (ndp->pr->rod > 0)
                        dfp = ndp->sd->rf;
                else
                        dfp = ndp->sd->rb;
        }
        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 backface visibility */
        if (!hitfront & !backvis) {
                raytrans(r);
                return(1);
        }
                                                /* check other rays to pass */
        if (nd.thick != 0 && (r->crtype & SHADOW ||
                                !(r->crtype & (SPECULAR|AMBIENT)) ||
                                (nd.thick > 0) ^ hitfront)) {
                raytrans(r);                    /* hide our proxy */
                return(1);
        }
        nd.mp = m;
        nd.pr = r;
                                                /* get BSDF data */
        nd.sd = loadBSDF(m->oargs.sarg[1]);
                                                /* early shadow check */
        if (r->crtype & SHADOW && (nd.sd->tf == NULL) & (nd.sd->tb == NULL))
                return(1);
                                                /* diffuse reflectance */
        if (hitfront) {
                cvt_sdcolor(nd.rdiff, &nd.sd->rLambFront);
                if (m->oargs.nfargs >= 3) {
                        setcolor(ctmp, m->oargs.farg[0],
                                        m->oargs.farg[1],
                                        m->oargs.farg[2]);
                        addcolor(nd.rdiff, ctmp);
                }
        } else {
                cvt_sdcolor(nd.rdiff, &nd.sd->rLambBack);
                if (m->oargs.nfargs >= 6) {
                        setcolor(ctmp, m->oargs.farg[3],
                                        m->oargs.farg[4],
                                        m->oargs.farg[5]);
                        addcolor(nd.rdiff, ctmp);
                }
        }
                                                /* diffuse transmittance */
        cvt_sdcolor(nd.tdiff, &nd.sd->tLamb);
        if (m->oargs.nfargs >= 9) {
                setcolor(ctmp, m->oargs.farg[6],
                                m->oargs.farg[7],
                                m->oargs.farg[8]);
                addcolor(nd.tdiff, ctmp);
        }
                                                /* 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) {
                objerror(m, WARNING, "Illegal orientation vector");
                return(1);
        }
        compute_through(&nd);                   /* compute through component */
        if (r->crtype & SHADOW) {
                RAY     tr;                     /* attempt to pass shadow ray */
                if (rayorigin(&tr, TRANS, r, nd.cthru) < 0)
                        return(1);              /* blocked */
                VCOPY(tr.rdir, r->rdir);
                rayvalue(&tr);                  /* transmit with scaling */
                multcolor(tr.rcol, tr.rcoef);
                copycolor(r->rcol, tr.rcol);
                return(1);                      /* we're done */
        }
        ec = SDinvXform(nd.fromloc, nd.toloc);
        if (!ec)                                /* 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 */
        if (bright(nd.rdiff) > FTINY) {         /* ambient from reflection */
                if (!hitfront)
                        flipsurface(r);
                copycolor(ctmp, nd.rdiff);
                multambient(ctmp, r, nd.pnorm);
                addcolor(r->rcol, ctmp);
                if (!hitfront)
                        flipsurface(r);
        }
        if (bright(nd.tdiff) > 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];
                copycolor(ctmp, nd.tdiff);
                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:	2.37
Committed:	Thu May 18 17:59:37 2017 UTC (7 years ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.36:	+19 -16 lines
Log Message:	Further tweak to make sure we never double-count