src/rt/m_bsdf.c

#ifndef lint
static const char RCSid[] = "$Id: m_bsdf.c,v 2.30 2015/09/02 18:59:01 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 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   rdiff;          /* diffuse reflection */
        COLOR   tdiff;          /* 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);
        }
        if (ambRayInPmap(np->pr))
                return;         /* specular already in photon map */
        /*
         *  Compute scattering coefficient using BSDF.
         */
        if (!direct_bsdf_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 reflection coefficient using BSDF.
         */
        if (!direct_bsdf_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 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->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 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);
        }
        nd.mp = m;
        nd.pr = r;
                                                /* get BSDF data */
        nd.sd = loadBSDF(m->oargs.sarg[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)
                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 */
        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:	2.31
Committed:	Fri Feb 17 23:24:56 2017 UTC (7 years, 3 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.30:	+31 -57 lines
Log Message:	Simplified handling of diffuse components
#	User	Rev	Content
1	greg	2.1	#ifndef lint
2	greg	2.31	static const char RCSid[] = "$Id: m_bsdf.c,v 2.30 2015/09/02 18:59:01 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	greg	2.30	#include "pmapmat.h"
17	greg	2.1
18			/*
19			* Arguments to this material include optional diffuse colors.
20			* String arguments include the BSDF and function files.
21	greg	2.5	* A non-zero thickness causes the strange but useful behavior
22			* of translating transmitted rays this distance beneath the surface
23			* (opposite the surface normal) to bypass any intervening geometry.
24			* Translation only affects scattered, non-source-directed samples.
25			* A non-zero thickness has the further side-effect that an unscattered
26	greg	2.1	* (view) ray will pass right through our material if it has any
27	greg	2.5	* non-diffuse transmission, making the BSDF surface invisible. This
28			* shows the proxied geometry instead. Thickness has the further
29			* effect of turning off reflection on the hidden side so that rays
30			* heading in the opposite direction pass unimpeded through the BSDF
31			* surface. A paired surface may be placed on the opposide side of
32			* the detail geometry, less than this thickness away, if a two-way
33			* proxy is desired. Note that the sign of the thickness is important.
34			* A positive thickness hides geometry behind the BSDF surface and uses
35			* front reflectance and transmission properties. A negative thickness
36			* hides geometry in front of the surface when rays hit from behind,
37			* and applies only the transmission and backside reflectance properties.
38			* Reflection is ignored on the hidden side, as those rays pass through.
39	greg	2.1	* The "up" vector for the BSDF is given by three variables, defined
40			* (along with the thickness) by the named function file, or '.' if none.
41			* Together with the surface normal, this defines the local coordinate
42			* system for the BSDF.
43			* We do not reorient the surface, so if the BSDF has no back-side
44	greg	2.5	* reflectance and none is given in the real arguments, a BSDF surface
45			* with zero thickness will appear black when viewed from behind
46			* unless backface visibility is off.
47			* The diffuse arguments are added to components in the BSDF file,
48	greg	2.1	* not multiplied. However, patterns affect this material as a multiplier
49			* on everything except non-diffuse reflection.
50			*
51			* Arguments for MAT_BSDF are:
52			* 6+ thick BSDFfile ux uy uz funcfile transform
53			* 0
54	greg	2.8	* 0\|3\|6\|9 rdf gdf bdf
55	greg	2.1	* rdb gdb bdb
56			* rdt gdt bdt
57			*/
58
59	greg	2.4	/*
60			* Note that our reverse ray-tracing process means that the positions
61			* of incoming and outgoing vectors may be reversed in our calls
62			* to the BSDF library. This is fine, since the bidirectional nature
63			* of the BSDF (that's what the 'B' stands for) means it all works out.
64			*/
65
66	greg	2.1	typedef struct {
67			OBJREC mp; / material pointer */
68			RAY pr; / intersected ray */
69			FVECT pnorm; /* perturbed surface normal */
70	greg	2.4	FVECT vray; /* local outgoing (return) vector */
71	greg	2.9	double sr_vpsa[2]; /* sqrt of BSDF projected solid angle extrema */
72	greg	2.1	RREAL toloc[3][3]; /* world to local BSDF coords */
73			RREAL fromloc[3][3]; /* local BSDF coords to world */
74			double thick; /* surface thickness */
75			SDData sd; / loaded BSDF data */
76	greg	2.31	COLOR rdiff; /* diffuse reflection */
77			COLOR tdiff; /* diffuse transmission */
78	greg	2.1	} BSDFDAT; /* BSDF material data */
79
80			#define cvt_sdcolor(cv, svp) ccy2rgb(&(svp)->spec, (svp)->cieY, cv)
81
82	greg	2.4	/* Jitter ray sample according to projected solid angle and specjitter */
83			static void
84	greg	2.15	bsdf_jitter(FVECT vres, BSDFDAT *ndp, double sr_psa)
85	greg	2.4	{
86			VCOPY(vres, ndp->vray);
87			if (specjitter < 1.)
88			sr_psa *= specjitter;
89			if (sr_psa <= FTINY)
90			return;
91			vres[0] += sr_psa*(.5 - frandom());
92			vres[1] += sr_psa*(.5 - frandom());
93			normalize(vres);
94			}
95
96	greg	2.7	/* Evaluate BSDF for direct component, returning true if OK to proceed */
97			static int
98	greg	2.13	direct_bsdf_OK(COLOR cval, FVECT ldir, double omega, BSDFDAT *ndp)
99	greg	2.7	{
100	greg	2.15	int nsamp, ok = 0;
101	greg	2.13	FVECT vsrc, vsmp, vjit;
102			double tomega;
103	greg	2.15	double sf, tsr, sd[2];
104	greg	2.13	COLOR csmp;
105	greg	2.7	SDValue sv;
106			SDError ec;
107	greg	2.13	int i;
108	greg	2.7	/* transform source direction */
109			if (SDmapDir(vsrc, ndp->toloc, ldir) != SDEnone)
110			return(0);
111	greg	2.16	/* assign number of samples */
112			ec = SDsizeBSDF(&tomega, ndp->vray, vsrc, SDqueryMin, ndp->sd);
113			if (ec)
114			goto baderror;
115	greg	2.13	/* check indirect over-counting */
116			if (ndp->thick != 0 && ndp->pr->crtype & (SPECULAR\|AMBIENT)
117			&& vsrc[2] > 0 ^ ndp->vray[2] > 0) {
118			double dx = vsrc[0] + ndp->vray[0];
119			double dy = vsrc[1] + ndp->vray[1];
120	greg	2.16	if (dxdx + dydy <= omega+tomega)
121	greg	2.7	return(0);
122			}
123	greg	2.15	sf = specjitter * ndp->pr->rweight;
124	greg	2.24	if (tomega <= .0)
125			nsamp = 1;
126			else if (25.*tomega <= omega)
127	greg	2.15	nsamp = 100.*sf + .5;
128			else
129			nsamp = 4.sfomega/tomega + .5;
130			nsamp += !nsamp;
131			setcolor(cval, .0, .0, .0); /* sample our source area */
132	greg	2.13	sf = sqrt(omega);
133	greg	2.15	tsr = sqrt(tomega);
134	greg	2.13	for (i = nsamp; i--; ) {
135			VCOPY(vsmp, vsrc); /* jitter query directions */
136			if (nsamp > 1) {
137			multisamp(sd, 2, (i + frandom())/(double)nsamp);
138			vsmp[0] += (sd[0] - .5)*sf;
139			vsmp[1] += (sd[1] - .5)*sf;
140			if (normalize(vsmp) == 0) {
141			--nsamp;
142			continue;
143			}
144			}
145	greg	2.15	bsdf_jitter(vjit, ndp, tsr);
146	greg	2.13	/* compute BSDF */
147			ec = SDevalBSDF(&sv, vjit, vsmp, ndp->sd);
148			if (ec)
149			goto baderror;
150			if (sv.cieY <= FTINY) /* worth using? */
151			continue;
152			cvt_sdcolor(csmp, &sv);
153			addcolor(cval, csmp); /* average it in */
154			++ok;
155			}
156			sf = 1./(double)nsamp;
157			scalecolor(cval, sf);
158			return(ok);
159			baderror:
160			objerror(ndp->mp, USER, transSDError(ec));
161	greg	2.17	return(0); /* gratis return */
162	greg	2.7	}
163
164	greg	2.5	/* Compute source contribution for BSDF (reflected & transmitted) */
165	greg	2.1	static void
166	greg	2.5	dir_bsdf(
167	greg	2.1	COLOR cval, /* returned coefficient */
168			void nnp, / material data */
169			FVECT ldir, /* light source direction */
170			double omega /* light source size */
171			)
172			{
173	greg	2.3	BSDFDAT np = (BSDFDAT )nnp;
174	greg	2.1	double ldot;
175			double dtmp;
176			COLOR ctmp;
177
178			setcolor(cval, .0, .0, .0);
179
180			ldot = DOT(np->pnorm, ldir);
181			if ((-FTINY <= ldot) & (ldot <= FTINY))
182			return;
183
184	greg	2.9	if (ldot > 0 && bright(np->rdiff) > FTINY) {
185	greg	2.1	/*
186			* Compute added diffuse reflected component.
187			*/
188			copycolor(ctmp, np->rdiff);
189			dtmp = ldot * omega * (1./PI);
190			scalecolor(ctmp, dtmp);
191			addcolor(cval, ctmp);
192			}
193	greg	2.9	if (ldot < 0 && bright(np->tdiff) > FTINY) {
194	greg	2.1	/*
195			* Compute added diffuse transmission.
196			*/
197			copycolor(ctmp, np->tdiff);
198			dtmp = -ldot * omega * (1.0/PI);
199			scalecolor(ctmp, dtmp);
200			addcolor(cval, ctmp);
201			}
202	greg	2.30	if (ambRayInPmap(np->pr))
203			return; /* specular already in photon map */
204	greg	2.1	/*
205			* Compute scattering coefficient using BSDF.
206			*/
207	greg	2.13	if (!direct_bsdf_OK(ctmp, ldir, omega, np))
208	greg	2.1	return;
209	greg	2.31	if (ldot < 0) { /* pattern for specular transmission */
210	greg	2.1	multcolor(ctmp, np->pr->pcol);
211			dtmp = -ldot * omega;
212	greg	2.31	} else
213			dtmp = ldot * omega;
214	greg	2.1	scalecolor(ctmp, dtmp);
215			addcolor(cval, ctmp);
216			}
217
218	greg	2.5	/* Compute source contribution for BSDF (reflected only) */
219			static void
220			dir_brdf(
221			COLOR cval, /* returned coefficient */
222			void nnp, / material data */
223			FVECT ldir, /* light source direction */
224			double omega /* light source size */
225			)
226			{
227			BSDFDAT np = (BSDFDAT )nnp;
228			double ldot;
229			double dtmp;
230			COLOR ctmp, ctmp1, ctmp2;
231
232			setcolor(cval, .0, .0, .0);
233
234			ldot = DOT(np->pnorm, ldir);
235
236			if (ldot <= FTINY)
237			return;
238
239			if (bright(np->rdiff) > FTINY) {
240			/*
241			* Compute added diffuse reflected component.
242			*/
243			copycolor(ctmp, np->rdiff);
244			dtmp = ldot * omega * (1./PI);
245			scalecolor(ctmp, dtmp);
246			addcolor(cval, ctmp);
247			}
248	greg	2.30	if (ambRayInPmap(np->pr))
249			return; /* specular already in photon map */
250	greg	2.5	/*
251			* Compute reflection coefficient using BSDF.
252			*/
253	greg	2.13	if (!direct_bsdf_OK(ctmp, ldir, omega, np))
254	greg	2.5	return;
255			dtmp = ldot * omega;
256			scalecolor(ctmp, dtmp);
257			addcolor(cval, ctmp);
258			}
259
260			/* Compute source contribution for BSDF (transmitted only) */
261			static void
262			dir_btdf(
263			COLOR cval, /* returned coefficient */
264			void nnp, / material data */
265			FVECT ldir, /* light source direction */
266			double omega /* light source size */
267			)
268			{
269			BSDFDAT np = (BSDFDAT )nnp;
270			double ldot;
271			double dtmp;
272			COLOR ctmp;
273
274			setcolor(cval, .0, .0, .0);
275
276			ldot = DOT(np->pnorm, ldir);
277
278			if (ldot >= -FTINY)
279			return;
280
281			if (bright(np->tdiff) > FTINY) {
282			/*
283			* Compute added diffuse transmission.
284			*/
285			copycolor(ctmp, np->tdiff);
286			dtmp = -ldot * omega * (1.0/PI);
287			scalecolor(ctmp, dtmp);
288			addcolor(cval, ctmp);
289			}
290	greg	2.30	if (ambRayInPmap(np->pr))
291			return; /* specular already in photon map */
292	greg	2.5	/*
293			* Compute scattering coefficient using BSDF.
294			*/
295	greg	2.13	if (!direct_bsdf_OK(ctmp, ldir, omega, np))
296	greg	2.5	return;
297			/* full pattern on transmission */
298			multcolor(ctmp, np->pr->pcol);
299			dtmp = -ldot * omega;
300			scalecolor(ctmp, dtmp);
301			addcolor(cval, ctmp);
302			}
303
304	greg	2.1	/* Sample separate BSDF component */
305			static int
306			sample_sdcomp(BSDFDAT ndp, SDComponent dcp, int usepat)
307			{
308			int nstarget = 1;
309	greg	2.11	int nsent;
310	greg	2.1	SDError ec;
311			SDValue bsv;
312	greg	2.11	double xrand;
313	greg	2.10	FVECT vsmp;
314	greg	2.1	RAY sr;
315			/* multiple samples? */
316			if (specjitter > 1.5) {
317			nstarget = specjitter*ndp->pr->rweight + .5;
318	greg	2.14	nstarget += !nstarget;
319	greg	2.1	}
320	greg	2.11	/* run through our samples */
321			for (nsent = 0; nsent < nstarget; nsent++) {
322	greg	2.15	if (nstarget == 1) { /* stratify random variable */
323	greg	2.11	xrand = urand(ilhash(dimlist,ndims)+samplendx);
324	greg	2.15	if (specjitter < 1.)
325			xrand = .5 + specjitter*(xrand-.5);
326			} else {
327	greg	2.11	xrand = (nsent + frandom())/(double)nstarget;
328	greg	2.15	}
329	greg	2.11	SDerrorDetail[0] = '\0'; /* sample direction & coef. */
330	greg	2.15	bsdf_jitter(vsmp, ndp, ndp->sr_vpsa[0]);
331	greg	2.11	ec = SDsampComponent(&bsv, vsmp, xrand, dcp);
332	greg	2.1	if (ec)
333	greg	2.2	objerror(ndp->mp, USER, transSDError(ec));
334	greg	2.11	if (bsv.cieY <= FTINY) /* zero component? */
335	greg	2.1	break;
336			/* map vector to world */
337	greg	2.4	if (SDmapDir(sr.rdir, ndp->fromloc, vsmp) != SDEnone)
338	greg	2.1	break;
339			/* spawn a specular ray */
340			if (nstarget > 1)
341			bsv.cieY /= (double)nstarget;
342	greg	2.11	cvt_sdcolor(sr.rcoef, &bsv); /* use sample color */
343			if (usepat) /* apply pattern? */
344	greg	2.1	multcolor(sr.rcoef, ndp->pr->pcol);
345			if (rayorigin(&sr, SPECULAR, ndp->pr, sr.rcoef) < 0) {
346	greg	2.11	if (maxdepth > 0)
347	greg	2.1	break;
348	greg	2.11	continue; /* Russian roulette victim */
349	greg	2.1	}
350	greg	2.5	/* need to offset origin? */
351	greg	2.9	if (ndp->thick != 0 && ndp->pr->rod > 0 ^ vsmp[2] > 0)
352	greg	2.5	VSUM(sr.rorg, sr.rorg, ndp->pr->ron, -ndp->thick);
353	greg	2.1	rayvalue(&sr); /* send & evaluate sample */
354			multcolor(sr.rcol, sr.rcoef);
355			addcolor(ndp->pr->rcol, sr.rcol);
356			}
357			return(nsent);
358			}
359
360			/* Sample non-diffuse components of BSDF */
361			static int
362			sample_sdf(BSDFDAT *ndp, int sflags)
363			{
364			int n, ntotal = 0;
365			SDSpectralDF *dfp;
366			COLORV *unsc;
367
368			if (sflags == SDsampSpT) {
369	greg	2.31	unsc = ndp->tdiff;
370	greg	2.22	if (ndp->pr->rod > 0)
371			dfp = (ndp->sd->tf != NULL) ? ndp->sd->tf : ndp->sd->tb;
372			else
373			dfp = (ndp->sd->tb != NULL) ? ndp->sd->tb : ndp->sd->tf;
374	greg	2.1	} else /* sflags == SDsampSpR */ {
375	greg	2.31	unsc = ndp->rdiff;
376			if (ndp->pr->rod > 0)
377	greg	2.1	dfp = ndp->sd->rf;
378	greg	2.31	else
379	greg	2.1	dfp = ndp->sd->rb;
380			}
381			if (dfp == NULL) /* no specular component? */
382			return(0);
383			/* below sampling threshold? */
384			if (dfp->maxHemi <= specthresh+FTINY) {
385	greg	2.3	if (dfp->maxHemi > FTINY) { /* XXX no color from BSDF */
386	greg	2.4	FVECT vjit;
387			double d;
388	greg	2.1	COLOR ctmp;
389	greg	2.15	bsdf_jitter(vjit, ndp, ndp->sr_vpsa[1]);
390	greg	2.4	d = SDdirectHemi(vjit, sflags, ndp->sd);
391	greg	2.1	if (sflags == SDsampSpT) {
392			copycolor(ctmp, ndp->pr->pcol);
393			scalecolor(ctmp, d);
394			} else /* no pattern on reflection */
395			setcolor(ctmp, d, d, d);
396			addcolor(unsc, ctmp);
397			}
398			return(0);
399			}
400			/* else need to sample */
401			dimlist[ndims++] = (int)(size_t)ndp->mp;
402			ndims++;
403			for (n = dfp->ncomp; n--; ) { /* loop over components */
404			dimlist[ndims-1] = n + 9438;
405			ntotal += sample_sdcomp(ndp, &dfp->comp[n], sflags==SDsampSpT);
406			}
407			ndims -= 2;
408			return(ntotal);
409			}
410
411			/* Color a ray that hit a BSDF material */
412			int
413			m_bsdf(OBJREC m, RAY r)
414			{
415	greg	2.6	int hitfront;
416	greg	2.1	COLOR ctmp;
417			SDError ec;
418	greg	2.5	FVECT upvec, vtmp;
419	greg	2.1	MFUNC *mf;
420			BSDFDAT nd;
421			/* check arguments */
422			if ((m->oargs.nsargs < 6) \| (m->oargs.nfargs > 9) \|
423			(m->oargs.nfargs % 3))
424			objerror(m, USER, "bad # arguments");
425	greg	2.6	/* record surface struck */
426	greg	2.9	hitfront = (r->rod > 0);
427	greg	2.1	/* load cal file */
428			mf = getfunc(m, 5, 0x1d, 1);
429	greg	2.25	setfunc(m, r);
430	greg	2.1	/* get thickness */
431			nd.thick = evalue(mf->ep[0]);
432	greg	2.5	if ((-FTINY <= nd.thick) & (nd.thick <= FTINY))
433	greg	2.1	nd.thick = .0;
434			/* check shadow */
435			if (r->crtype & SHADOW) {
436	greg	2.9	if (nd.thick != 0)
437	greg	2.3	raytrans(r); /* pass-through */
438	greg	2.5	return(1); /* or shadow */
439	greg	2.1	}
440	greg	2.26	/* check backface visibility */
441			if (!hitfront & !backvis) {
442			raytrans(r);
443			return(1);
444			}
445	greg	2.5	/* check other rays to pass */
446	greg	2.9	if (nd.thick != 0 && (!(r->crtype & (SPECULAR\|AMBIENT)) \|\|
447	greg	2.29	(nd.thick > 0) ^ hitfront)) {
448	greg	2.5	raytrans(r); /* hide our proxy */
449	greg	2.1	return(1);
450			}
451	greg	2.31	nd.mp = m;
452			nd.pr = r;
453	greg	2.5	/* get BSDF data */
454			nd.sd = loadBSDF(m->oargs.sarg[1]);
455	greg	2.1	/* diffuse reflectance */
456	greg	2.6	if (hitfront) {
457	greg	2.31	cvt_sdcolor(nd.rdiff, &nd.sd->rLambFront);
458			if (m->oargs.nfargs >= 3) {
459			setcolor(ctmp, m->oargs.farg[0],
460	greg	2.1	m->oargs.farg[1],
461			m->oargs.farg[2]);
462	greg	2.31	addcolor(nd.rdiff, ctmp);
463			}
464	greg	2.1	} else {
465	greg	2.31	cvt_sdcolor(nd.rdiff, &nd.sd->rLambBack);
466			if (m->oargs.nfargs >= 6) {
467			setcolor(ctmp, m->oargs.farg[3],
468	greg	2.1	m->oargs.farg[4],
469			m->oargs.farg[5]);
470	greg	2.31	addcolor(nd.rdiff, ctmp);
471			}
472	greg	2.1	}
473			/* diffuse transmittance */
474	greg	2.31	cvt_sdcolor(nd.tdiff, &nd.sd->tLamb);
475			if (m->oargs.nfargs >= 9) {
476			setcolor(ctmp, m->oargs.farg[6],
477	greg	2.1	m->oargs.farg[7],
478			m->oargs.farg[8]);
479	greg	2.31	addcolor(nd.tdiff, ctmp);
480			}
481	greg	2.1	/* get modifiers */
482			raytexture(r, m->omod);
483			/* modify diffuse values */
484			multcolor(nd.rdiff, r->pcol);
485			multcolor(nd.tdiff, r->pcol);
486			/* get up vector */
487			upvec[0] = evalue(mf->ep[1]);
488			upvec[1] = evalue(mf->ep[2]);
489			upvec[2] = evalue(mf->ep[3]);
490			/* return to world coords */
491	greg	2.21	if (mf->fxp != &unitxf) {
492			multv3(upvec, upvec, mf->fxp->xfm);
493			nd.thick *= mf->fxp->sca;
494	greg	2.1	}
495	greg	2.23	if (r->rox != NULL) {
496			multv3(upvec, upvec, r->rox->f.xfm);
497			nd.thick *= r->rox->f.sca;
498			}
499	greg	2.1	raynormal(nd.pnorm, r);
500			/* compute local BSDF xform */
501			ec = SDcompXform(nd.toloc, nd.pnorm, upvec);
502			if (!ec) {
503	greg	2.4	nd.vray[0] = -r->rdir[0];
504			nd.vray[1] = -r->rdir[1];
505			nd.vray[2] = -r->rdir[2];
506			ec = SDmapDir(nd.vray, nd.toloc, nd.vray);
507	greg	2.20	}
508			if (!ec)
509			ec = SDinvXform(nd.fromloc, nd.toloc);
510	greg	2.19	if (ec) {
511			objerror(m, WARNING, "Illegal orientation vector");
512			return(1);
513	greg	2.1	}
514	greg	2.4	/* determine BSDF resolution */
515	greg	2.20	ec = SDsizeBSDF(nd.sr_vpsa, nd.vray, NULL, SDqueryMin+SDqueryMax, nd.sd);
516			if (ec)
517			objerror(m, USER, transSDError(ec));
518
519	greg	2.9	nd.sr_vpsa[0] = sqrt(nd.sr_vpsa[0]);
520			nd.sr_vpsa[1] = sqrt(nd.sr_vpsa[1]);
521	greg	2.6	if (!hitfront) { /* perturb normal towards hit */
522	greg	2.1	nd.pnorm[0] = -nd.pnorm[0];
523			nd.pnorm[1] = -nd.pnorm[1];
524			nd.pnorm[2] = -nd.pnorm[2];
525			}
526			/* sample reflection */
527			sample_sdf(&nd, SDsampSpR);
528			/* sample transmission */
529			sample_sdf(&nd, SDsampSpT);
530			/* compute indirect diffuse */
531	greg	2.31	if (bright(nd.rdiff) > FTINY) { /* ambient from reflection */
532	greg	2.6	if (!hitfront)
533	greg	2.1	flipsurface(r);
534	greg	2.31	copycolor(ctmp, nd.rdiff);
535	greg	2.1	multambient(ctmp, r, nd.pnorm);
536			addcolor(r->rcol, ctmp);
537	greg	2.6	if (!hitfront)
538	greg	2.1	flipsurface(r);
539			}
540	greg	2.31	if (bright(nd.tdiff) > FTINY) { /* ambient from other side */
541	greg	2.1	FVECT bnorm;
542	greg	2.6	if (hitfront)
543	greg	2.1	flipsurface(r);
544			bnorm[0] = -nd.pnorm[0];
545			bnorm[1] = -nd.pnorm[1];
546			bnorm[2] = -nd.pnorm[2];
547	greg	2.31	copycolor(ctmp, nd.tdiff);
548	greg	2.9	if (nd.thick != 0) { /* proxy with offset? */
549	greg	2.5	VCOPY(vtmp, r->rop);
550	greg	2.18	VSUM(r->rop, vtmp, r->ron, nd.thick);
551	greg	2.5	multambient(ctmp, r, bnorm);
552			VCOPY(r->rop, vtmp);
553			} else
554			multambient(ctmp, r, bnorm);
555	greg	2.1	addcolor(r->rcol, ctmp);
556	greg	2.6	if (hitfront)
557	greg	2.1	flipsurface(r);
558			}
559			/* add direct component */
560	greg	2.22	if ((bright(nd.tdiff) <= FTINY) & (nd.sd->tf == NULL) &
561			(nd.sd->tb == NULL)) {
562	greg	2.5	direct(r, dir_brdf, &nd); /* reflection only */
563	greg	2.9	} else if (nd.thick == 0) {
564	greg	2.5	direct(r, dir_bsdf, &nd); /* thin surface scattering */
565			} else {
566			direct(r, dir_brdf, &nd); /* reflection first */
567			VCOPY(vtmp, r->rop); /* offset for transmitted */
568			VSUM(r->rop, vtmp, r->ron, -nd.thick);
569	greg	2.6	direct(r, dir_btdf, &nd); /* separate transmission */
570	greg	2.5	VCOPY(r->rop, vtmp);
571			}
572	greg	2.1	/* clean up */
573			SDfreeCache(nd.sd);
574			return(1);
575			}