src/rt/m_bsdf.c

#ifndef lint
static const char RCSid[] = "$Id: m_bsdf.c,v 2.61 2020/07/09 17:32:31 greg Exp $";
#endif
/*
 *  Shading for materials with BSDFs taken from XML data files
 */

#include "copyright.h"

#include  "ray.h"
#include  "otypes.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.
 *      For the MAT_BSDF type, a non-zero thickness causes the 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.
 *      For the MAT_ABSDF type, we check for a strong "through" component.
 *  Such a component will cause direct rays to pass through unscattered.
 *  A separate test prevents over-counting by dropping samples that are
 *  too close to this "through" direction.  BSDFs with such a through direction
 *  will also have a view component, meaning they are somewhat see-through.
 *  A MAT_BSDF type with zero thickness behaves the same as a MAT_ABSDF
 *  type with no strong through component.
 *      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_ABSDF are:
 *      5+      BSDFfile        ux uy uz        funcfile        transform
 *      0
 *      0|3|6|9 rdf     gdf     bdf
 *              rdb     gdb     bdb
 *              rdt     gdt     bdt
 *
 *  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 for MAT_ABSDF */
        COLOR   cthru_surr;     /* surround for "through" component */
        SDData  *sd;            /* loaded BSDF data */
        COLOR   rdiff;          /* diffuse reflection */
        COLOR   runsamp;        /* BSDF hemispherical reflection */
        COLOR   tdiff;          /* diffuse transmission */
        COLOR   tunsamp;        /* BSDF hemispherical transmission */
}  BSDFDAT;             /* BSDF material data */

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

typedef struct {
        double  vy;             /* brightness (for sorting) */
        FVECT   tdir;           /* through sample direction (normalized) */
        COLOR   vcol;           /* BTDF color */
}  PEAKSAMP;            /* BTDF peak sample */

/* Comparison function to put near-peak values in descending order */
static int
cmp_psamp(const void *p1, const void *p2)
{
        double  diff = (*(const PEAKSAMP *)p1).vy - (*(const PEAKSAMP *)p2).vy;
        if (diff > 0) return(-1);
        if (diff < 0) return(1);
        return(0);
}

/* Compute "through" component color for MAT_ABSDF */
static void
compute_through(BSDFDAT *ndp)
{
#define NDIR2CHECK      29
        static const float      dir2check[NDIR2CHECK][2] = {
                                        {0, 0}, {-0.6, 0}, {0, 0.6},
                                        {0, -0.6}, {0.6, 0}, {-0.6, 0.6},
                                        {-0.6, -0.6}, {0.6, 0.6}, {0.6, -0.6},
                                        {-1.2, 0}, {0, 1.2}, {0, -1.2},
                                        {1.2, 0}, {-1.2, 1.2}, {-1.2, -1.2},
                                        {1.2, 1.2}, {1.2, -1.2}, {-1.8, 0},
                                        {0, 1.8}, {0, -1.8}, {1.8, 0},
                                        {-1.8, 1.8}, {-1.8, -1.8}, {1.8, 1.8},
                                        {1.8, -1.8}, {-2.4, 0}, {0, 2.4},
                                        {0, -2.4}, {2.4, 0},
                                };
        const double    peak_over = 1.5;
        PEAKSAMP        psamp[NDIR2CHECK];
        SDSpectralDF    *dfp;
        FVECT           pdir;
        double          tomega, srchrad;
        double          tomsum, tomsurr;
        COLOR           vpeak, vsurr;
        double          vypeak;
        int             i, ns;
        SDError         ec;

        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 evaluate peak */
        for (i = 0; i < NDIR2CHECK; i++) {
                SDValue sv;
                psamp[i].tdir[0] = -ndp->vray[0] + dir2check[i][0]*srchrad;
                psamp[i].tdir[1] = -ndp->vray[1] + dir2check[i][1]*srchrad;
                psamp[i].tdir[2] = -ndp->vray[2];
                normalize(psamp[i].tdir);
                ec = SDevalBSDF(&sv, psamp[i].tdir, ndp->vray, ndp->sd);
                if (ec)
                        goto baderror;
                cvt_sdcolor(psamp[i].vcol, &sv);
                psamp[i].vy = sv.cieY;
        }
        qsort(psamp, NDIR2CHECK, sizeof(PEAKSAMP), cmp_psamp);
        if (psamp[0].vy <= FTINY)
                return;                         /* zero area */
        setcolor(vpeak, 0, 0, 0);
        setcolor(vsurr, 0, 0, 0);
        vypeak = tomsum = tomsurr = 0;          /* combine top unique values */
        ns = 0;
        for (i = 0; i < NDIR2CHECK; i++) {
                if (i && psamp[i].vy == psamp[i-1].vy)
                        continue;               /* assume duplicate sample */

                ec = SDsizeBSDF(&tomega, psamp[i].tdir, ndp->vray,
                                                SDqueryMin, ndp->sd);
                if (ec)
                        goto baderror;
                                                /* not really a peak? */
                if (tomega > 1.5*dfp->minProjSA ||
                                        vypeak > 8.*psamp[i].vy*ns) {
                        if (!i) return;         /* abort */
                        scalecolor(psamp[i].vcol, tomega);
                        addcolor(vsurr, psamp[i].vcol);
                        tomsurr += tomega;
                        continue;
                }
                scalecolor(psamp[i].vcol, tomega);
                addcolor(vpeak, psamp[i].vcol);
                tomsum += tomega;
                vypeak += psamp[i].vy;
                ++ns;
        }
        if (vypeak*tomsurr < peak_over*bright(vsurr)*ns)
                return;                         /* peak not peaky enough */
        if ((vypeak/ns - (ndp->vray[2] > 0 ? ndp->sd->tLambFront.cieY
                        : ndp->sd->tLambBack.cieY)*(1./PI))*tomsum <= .001)
                return;                         /* < 0.1% transmission */
        copycolor(ndp->cthru, vpeak);           /* already scaled by omega */
        multcolor(ndp->cthru, ndp->pr->pcol);   /* modify by pattern */
        if (tomsurr > FTINY) {                  /* surround contribution? */
                scalecolor(vsurr, 1./tomsurr);  /* this one is avg. BTDF */
                copycolor(ndp->cthru_surr, vsurr);
                multcolor(ndp->cthru_surr, ndp->pr->pcol);
        }
        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;
        double  wtot = 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;
        case 1:
                if ((ndp->sd->tf == NULL) & (ndp->sd->tb == NULL))
                        return(0);      /* all diffuse */
                sv = ndp->sd->tLambFront;
                break;
        case 2:
                if ((ndp->sd->tf == NULL) & (ndp->sd->tb == NULL))
                        return(0);      /* all diffuse */
                sv = ndp->sd->tLambBack;
                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 angle */
        omega *= fabs(vsrc[2]);
                                        /* check indirect over-counting */
        if ((vsrc[2] > 0) ^ (ndp->vray[2] > 0) && bright(ndp->cthru) > FTINY) {
                double          dx = vsrc[0] + ndp->vray[0];
                double          dy = vsrc[1] + ndp->vray[1];
                SDSpectralDF    *dfp = (ndp->pr->rod > 0) ?
                        ((ndp->sd->tf != NULL) ? ndp->sd->tf : ndp->sd->tb) :
                        ((ndp->sd->tb != NULL) ? ndp->sd->tb : ndp->sd->tf) ;

                if (dx*dx + dy*dy <= (2.5*4./PI)*(omega + dfp->minProjSA +
                                                2.*sqrt(omega*dfp->minProjSA))) {
                        if (bright(ndp->cthru_surr) <= FTINY)
                                return(0);
                        copycolor(cval, ndp->cthru_surr);
                        return(1);      /* return non-zero surround BTDF */
                }
        }
        ec = SDsizeBSDF(&tomega, ndp->vray, vsrc, SDqueryMin, ndp->sd);
        if (ec)
                goto baderror;
                                        /* 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);
#if 0
                if (sf < 2.5*tsr) {     /* weight by BSDF for small sources */
                        scalecolor(csmp, sv.cieY);
                        wtot += sv.cieY;
                } else
#endif
                wtot += 1.;
                addcolor(cval, csmp);
        }
        if (wtot <= FTINY)              /* no valid specular samples? */
                return(0);

        sf = 1./wtot;                   /* weighted 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 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 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 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 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 xmit)
{
        const int       hasthru = (xmit &&
                                        !(ndp->pr->crtype & (SPECULAR|AMBIENT))
                                        && bright(ndp->cthru) > FTINY);
        int             nstarget = 1;
        int             nsent = 0;
        int             n;
        SDError         ec;
        SDValue         bsv;
        double          xrand;
        FVECT           vsmp, vinc;
        RAY             sr;
                                                /* multiple samples? */
        if (specjitter > 1.5) {
                nstarget = specjitter*ndp->pr->rweight + .5;
                nstarget += !nstarget;
        }
                                                /* run through our samples */
        for (n = 0; n < nstarget; n++) {
                if (nstarget == 1) {            /* stratify random variable */
                        xrand = urand(ilhash(dimlist,ndims)+samplendx);
                        if (specjitter < 1.)
                                xrand = .5 + specjitter*(xrand-.5);
                } else {
                        xrand = (n + frandom())/(double)nstarget;
                }
                SDerrorDetail[0] = '\0';        /* sample direction & coef. */
                bsdf_jitter(vsmp, ndp, ndp->sr_vpsa[0]);
                VCOPY(vinc, vsmp);              /* to compare after */
                ec = SDsampComponent(&bsv, vsmp, xrand, dcp);
                if (ec)
                        objerror(ndp->mp, USER, transSDError(ec));
                if (bsv.cieY <= FTINY)          /* zero component? */
                        break;
                if (hasthru) {                  /* check for view ray */
                        double  dx = vinc[0] + vsmp[0];
                        double  dy = vinc[1] + vsmp[1];
                        if (dx*dx + dy*dy <= ndp->sr_vpsa[0]*ndp->sr_vpsa[0])
                                continue;       /* exclude view sample */
                }
                                                /* map non-view sample->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 (xmit)                       /* apply pattern on transmit */
                        multcolor(sr.rcoef, ndp->pr->pcol);
                if (rayorigin(&sr, SPECULAR, ndp->pr, sr.rcoef) < 0) {
                        if (!n & (nstarget > 1)) {
                                n = nstarget;   /* avoid infinitue loop */
                                nstarget = nstarget*sr.rweight/minweight;
                                if (n == nstarget) break;
                                n = -1;         /* moved target */
                        }
                        continue;               /* try again */
                }
                if (xmit && ndp->thick != 0)    /* need to offset origin? */
                        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);
                ++nsent;
        }
        return(nsent);
}

/* Sample non-diffuse components of BSDF */
static int
sample_sdf(BSDFDAT *ndp, int sflags)
{
        int             hasthru = (sflags == SDsampSpT &&
                                        !(ndp->pr->crtype & (SPECULAR|AMBIENT))
                                        && bright(ndp->cthru) > FTINY);
        int             n, ntotal = 0;
        double          b = 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;
        } else /* sflags == SDsampSpR */ {
                unsc = ndp->runsamp;
                if (ndp->pr->rod > 0)
                        dfp = ndp->sd->rf;
                else
                        dfp = ndp->sd->rb;
        }
        setcolor(unsc,  0, 0, 0);
        if (dfp == NULL)                        /* no specular component? */
                return(0);

        if (hasthru) {                          /* separate view sample? */
                RAY     tr;
                if (rayorigin(&tr, TRANS, ndp->pr, ndp->cthru) == 0) {
                        VCOPY(tr.rdir, ndp->pr->rdir);
                        rayvalue(&tr);
                        multcolor(tr.rcol, tr.rcoef);
                        addcolor(ndp->pr->rcol, tr.rcol);
                        ndp->pr->rxt = ndp->pr->rot + raydistance(&tr);
                        ++ntotal;
                        b = bright(ndp->cthru);
                } else
                        hasthru = 0;
        }
        if (dfp->maxHemi - b <= FTINY) {        /* have specular to sample? */
                b = 0;
        } else {
                FVECT   vjit;
                bsdf_jitter(vjit, ndp, ndp->sr_vpsa[1]);
                b = SDdirectHemi(vjit, sflags, ndp->sd) - b;
                if (b < 0) b = 0;
        }
        if (b <= specthresh+FTINY) {            /* below sampling threshold? */
                if (b > FTINY) {                /* XXX no color from BSDF */
                        if (sflags == SDsampSpT) {
                                copycolor(unsc, ndp->pr->pcol);
                                scalecolor(unsc, b);
                        } else                  /* no pattern on reflection */
                                setcolor(unsc, b, b, b);
                }
                return(ntotal);
        }
        dimlist[ndims] = (int)(size_t)ndp->mp;  /* else sample specular */
        ndims += 2;
        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     hasthick = (m->otype == MAT_BSDF);
        int     hitfront;
        COLOR   ctmp;
        SDError ec;
        FVECT   upvec, vtmp;
        MFUNC   *mf;
        BSDFDAT nd;
                                                /* check arguments */
        if ((m->oargs.nsargs < hasthick+5) | (m->oargs.nfargs > 9) |
                                (m->oargs.nfargs % 3))
                objerror(m, USER, "bad # arguments");
                                                /* record surface struck */
        hitfront = (r->rod > 0);
                                                /* load cal file */
        mf = hasthick   ? getfunc(m, 5, 0x1d, 1)
                        : getfunc(m, 4, 0xe, 1) ;
        setfunc(m, r);
        nd.thick = 0;                           /* set thickness */
        if (hasthick) {
                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);
        }
        if (hasthick && r->crtype & SHADOW)     /* early shadow check #1 */
                return(1);
        nd.mp = m;
        nd.pr = r;
                                                /* get BSDF data */
        nd.sd = loadBSDF(m->oargs.sarg[hasthick]);
                                                /* early shadow check #2 */
        if (r->crtype & SHADOW && (nd.sd->tf == NULL) & (nd.sd->tb == NULL)) {
                SDfreeCache(nd.sd);
                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, hitfront ? &nd.sd->tLambFront : &nd.sd->tLambBack);
        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[hasthick+0]);
        upvec[1] = evalue(mf->ep[hasthick+1]);
        upvec[2] = evalue(mf->ep[hasthick+2]);
                                                /* 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");
                SDfreeCache(nd.sd);
                return(1);
        }
        setcolor(nd.cthru, 0, 0, 0);            /* consider through component */
        setcolor(nd.cthru_surr, 0, 0, 0);
        if (m->otype == MAT_ABSDF) {
                compute_through(&nd);
                if (r->crtype & SHADOW) {
                        RAY     tr;             /* attempt to pass shadow ray */
                        SDfreeCache(nd.sd);
                        if (rayorigin(&tr, TRANS, r, nd.cthru) < 0)
                                return(1);      /* no through component */
                        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 */
        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:	2.62
Committed:	Sat Mar 27 17:50:18 2021 UTC (4 years, 1 month ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.61:	+11 -5 lines
Log Message:	fix: Allow different front/back diffuse reflectance in BSDF library