src/common/bsdf_t.c

#ifndef lint
static const char RCSid[] = "$Id: bsdf_t.c,v 3.53 2021/12/15 01:38:50 greg Exp $";
#endif
/*
 *  bsdf_t.c
 *  
 *  Definitions for variable-resolution BSDF trees
 *
 *  Created by Greg Ward on 2/2/11.
 *
 */

#define _USE_MATH_DEFINES
#include "rtio.h"
#include <stdlib.h>
#include <math.h>
#include <ctype.h>
#include "ezxml.h"
#include "bsdf.h"
#include "bsdf_t.h"
#include "hilbert.h"

/* Callback function type for SDtraverseTre() */
typedef int     SDtreCallback(float val, const double *cmin, double csiz,
                                                void *cptr);
                                        /* reference width maximum (1.0) */
static const unsigned   iwbits = sizeof(unsigned)*4;
static const unsigned   iwmax = 1<<(sizeof(unsigned)*4);
                                        /* maximum cumulative value */
static const unsigned   cumlmax = ~0;
                                        /* constant z-vector */
static const FVECT      zvec = {.0, .0, 1.};
                                        /* quantization value */
static double           quantum = 1./256.;
                                        /* our RGB primaries */
static C_COLOR          tt_RGB_prim[3];
static float            tt_RGB_coef[3];

static const double     czero[SD_MAXDIM];

enum {tt_Y, tt_u, tt_v};                /* tree components (tt_Y==0) */

/* Struct used for our distribution-building callback */
typedef struct {
        short           nic;            /* number of input coordinates */
        short           rev;            /* reversing query */
        unsigned        alen;           /* current array length */
        unsigned        nall;           /* number of allocated entries */
        unsigned        wmin;           /* minimum square size so far */
        unsigned        wmax;           /* maximum square size */
        struct outdir_s {
                unsigned        hent;           /* entering Hilbert index */
                int             wid;            /* this square size */
                float           bsdf;           /* BSDF for this square */
        }               *darr;          /* output direction array */
} SDdistScaffold;

/* Allocate a new scattering distribution node */
static SDNode *
SDnewNode(int nd, int lg)
{
        SDNode  *st;
        
        if (nd <= 0) {
                strcpy(SDerrorDetail, "Zero dimension BSDF node request");
                return NULL;
        }
        if (nd > SD_MAXDIM) {
                sprintf(SDerrorDetail, "Illegal BSDF dimension (%d > %d)",
                                nd, SD_MAXDIM);
                return NULL;
        }
        if (lg < 0) {
                st = (SDNode *)malloc(sizeof(SDNode) +
                                sizeof(st->u.t[0])*((1<<nd) - 1));
                if (st == NULL) {
                        sprintf(SDerrorDetail,
                                "Cannot allocate %d branch BSDF tree", 1<<nd);
                        return NULL;
                }
                memset(st->u.t, 0, sizeof(st->u.t[0])<<nd);
        } else {
                st = (SDNode *)malloc(sizeof(SDNode) +
                                sizeof(st->u.v[0])*((1 << nd*lg) - 1));         
                if (st == NULL) {
                        sprintf(SDerrorDetail,
                                "Cannot allocate %d BSDF leaves", 1 << nd*lg);
                        return NULL;
                }
        }
        st->ndim = nd;
        st->log2GR = lg;
        return st;
}

/* Free an SD tree */
static void
SDfreeTre(SDNode *st)
{
        int     n;

        if (st == NULL)
                return;
        for (n = (st->log2GR < 0) << st->ndim; n--; )
                SDfreeTre(st->u.t[n]);
        free(st);
}

/* Free a variable-resolution BSDF */
static void
SDFreeBTre(void *p)
{
        SDTre   *sdt = (SDTre *)p;

        if (sdt == NULL)
                return;
        SDfreeTre(sdt->stc[tt_Y]);
        SDfreeTre(sdt->stc[tt_u]);
        SDfreeTre(sdt->stc[tt_v]);
        free(sdt);
}

/* Fill branch's worth of grid values from subtree */
static void
fill_grid_branch(float *dptr, const float *sptr, int nd, int shft)
{
        unsigned        n = 1 << (shft-1);

        if (!--nd) {                    /* end on the line */
                memcpy(dptr, sptr, sizeof(*dptr)*n);
                return;
        }
        while (n--)                     /* recurse on each slice */
                fill_grid_branch(dptr + (n << shft*nd),
                                sptr + (n << (shft-1)*nd), nd, shft);
}

/* Get pointer at appropriate offset for the given branch */
static float *
grid_branch_start(SDNode *st, int n)
{
        unsigned        skipsiz = 1 << (st->log2GR - 1);
        float           *vptr = st->u.v;
        int             i;

        for (i = st->ndim; i--; skipsiz <<= st->log2GR)
                if (1<<i & n)
                        vptr += skipsiz;
        return vptr;
}

/* Simplify (consolidate) a tree by flattening uniform depth regions */
static SDNode *
SDsimplifyTre(SDNode *st)
{
        int             match, n;

        if (st == NULL)                 /* check for invalid tree */
                return NULL;
        if (st->log2GR >= 0)            /* grid just returns unaltered */
                return st;
        match = 1;                      /* check if grids below match */
        for (n = 0; n < 1<<st->ndim; n++) {
                if ((st->u.t[n] = SDsimplifyTre(st->u.t[n])) == NULL)
                        return NULL;    /* propogate error up call stack */
                match &= (st->u.t[n]->log2GR == st->u.t[0]->log2GR);
        }
        if (match && (match = st->u.t[0]->log2GR) >= 0) {
                SDNode  *stn = SDnewNode(st->ndim, match + 1);
                if (stn == NULL)        /* out of memory? */
                        return st;
                                        /* transfer values to new grid */
                for (n = 1 << st->ndim; n--; )
                        fill_grid_branch(grid_branch_start(stn, n),
                                        st->u.t[n]->u.v, stn->ndim, stn->log2GR);
                SDfreeTre(st);          /* free old tree */
                st = stn;               /* return new one */
        }
        return st;
}

/* Assign the given voxel in tree (produces no grid nodes) */
static SDNode *
SDsetVoxel(SDNode *sroot, int nd, const double *tmin, const double tsiz, float val)
{
        double  ctrk[SD_MAXDIM];
        double  csiz = 1.;
        SDNode  *st;
        int     i, n;
                                        /* check arguments */
        for (i = nd; i-- > 0; )
                if ((tmin[i] < .0) | (tmin[i] >= 1.-FTINY))
                        break;
        if ((i >= 0) | (nd <= 0) | (tsiz <= FTINY) | (tsiz > 1.+FTINY) |
                        (sroot != NULL && sroot->ndim != nd)) {
                SDfreeTre(sroot);
                return NULL;
        }
        if (tsiz >= 1.-FTINY) {         /* special case when tree is a leaf */
                SDfreeTre(sroot);
                if ((sroot = SDnewNode(nd, 0)) != NULL)
                        sroot->u.v[0] = val;
                return sroot;
        }
                                        /* make sure we have branching root */
        if (sroot != NULL && sroot->log2GR >= 0) {
                SDfreeTre(sroot); sroot = NULL;
        }
        if (sroot == NULL && (sroot = SDnewNode(nd, -1)) == NULL)
                return NULL;
        st = sroot;                     /* climb/grow tree */
        memset(ctrk, 0, sizeof(ctrk));
        for ( ; ; ) {
                csiz *= .5;             /* find appropriate branch */
                n = 0;
                for (i = nd; i--; )
                        if (ctrk[i]+csiz <= tmin[i]+FTINY) {
                                ctrk[i] += csiz;
                                n |= 1 << i;
                        }
                                        /* reached desired voxel? */
                if (csiz <= tsiz+FTINY) {
                        SDfreeTre(st->u.t[n]);
                        st = st->u.t[n] = SDnewNode(nd, 0);
                        break;
                }
                                        /* else grow tree as needed */
                if (st->u.t[n] != NULL && st->u.t[n]->log2GR >= 0) {
                        SDfreeTre(st->u.t[n]); st->u.t[n] = NULL;
                }
                if (st->u.t[n] == NULL)
                        st->u.t[n] = SDnewNode(nd, -1);
                if ((st = st->u.t[n]) == NULL)
                        break;
        }
        if (st == NULL) {
                SDfreeTre(sroot);
                return NULL;
        }
        st->u.v[0] = val;               /* assign leaf and return root */
        return sroot;
}

/* Find smallest leaf in tree */
static double
SDsmallestLeaf(const SDNode *st)
{
        if (st->log2GR < 0) {           /* tree branches */
                double  lmin = 1.;
                int     n;
                for (n = 1<<st->ndim; n--; ) {
                        double  lsiz = SDsmallestLeaf(st->u.t[n]);
                        if (lsiz < lmin)
                                lmin = lsiz;
                }
                return .5*lmin;
        }
                                        /* leaf grid width */
        return 1. / (double)(1 << st->log2GR);
}

/* Add up N-dimensional hypercube array values over the given box */
static double
SDiterSum(const float *va, int nd, int shft, const int *imin, const int *imax)
{
        const unsigned  skipsiz = 1 << --nd*shft;
        double          sum = .0;
        int             i;

        va += *imin * skipsiz;

        if (skipsiz == 1)
                for (i = *imin; i < *imax; i++)
                        sum += *va++;
        else
                for (i = *imin; i < *imax; i++, va += skipsiz)
                        sum += SDiterSum(va, nd, shft, imin+1, imax+1);
        return sum;
}

/* Average BSDF leaves over an orthotope defined by the unit hypercube */
static double
SDavgTreBox(const SDNode *st, const double *bmin, const double *bmax)
{
        unsigned        n;
        int             i;

        if (!st)
                return .0;
                                        /* check box limits */
        for (i = st->ndim; i--; ) {
                if (bmin[i] >= 1.)
                        return .0;
                if (bmax[i] <= 0)
                        return .0;
                if (bmin[i] >= bmax[i])
                        return .0;
        }
        if (st->log2GR < 0) {           /* iterate on subtree */
                double          sum = .0, wsum = 1e-20;
                double          sbmin[SD_MAXDIM], sbmax[SD_MAXDIM], w;
                for (n = 1 << st->ndim; n--; ) {
                        w = 1.;
                        for (i = st->ndim; i--; ) {
                                sbmin[i] = 2.*bmin[i];
                                sbmax[i] = 2.*bmax[i];
                                if (n & 1<<i) {
                                        sbmin[i] -= 1.;
                                        sbmax[i] -= 1.;
                                }
                                if (sbmin[i] < .0) sbmin[i] = .0;
                                if (sbmax[i] > 1.) sbmax[i] = 1.;
                                if (sbmin[i] >= sbmax[i]) {
                                        w = .0;
                                        break;
                                }
                                w *= sbmax[i] - sbmin[i];
                        }
                        if (w > 1e-10) {
                                sum += w * SDavgTreBox(st->u.t[n], sbmin, sbmax);
                                wsum += w;
                        }
                }
                return sum / wsum;
        } else {                        /* iterate over leaves */
                int             imin[SD_MAXDIM], imax[SD_MAXDIM];

                n = 1;
                for (i = st->ndim; i--; ) {
                        imin[i] = (bmin[i] <= 0) ? 0 :
                                        (int)((1 << st->log2GR)*bmin[i]);
                        imax[i] = (bmax[i] >= 1.) ? (1 << st->log2GR) :
                                (int)((1 << st->log2GR)*bmax[i] + .999999);
                        n *= imax[i] - imin[i];
                }
                if (n)
                        return SDiterSum(st->u.v, st->ndim,
                                        st->log2GR, imin, imax) / (double)n;
        }
        return .0;
}

/* Recursive call for SDtraverseTre() */
static int
SDdotravTre(const SDNode *st, const double *pos, int cmask,
                                SDtreCallback *cf, void *cptr,
                                const double *cmin, double csiz)
{
        int     rv, rval = 0;
        double  bmin[SD_MAXDIM];
        int     i, n;
                                        /* paranoia */
        if (st == NULL)
                return 0;
                                        /* in branches? */
        if (st->log2GR < 0) {
                unsigned        skipmask = 0;
                csiz *= .5;
                for (i = st->ndim; i--; )
                        if (1<<i & cmask) {
                                if (pos[i] < cmin[i] + csiz)
                                        for (n = 1 << st->ndim; n--; ) {
                                                if (n & 1<<i)
                                                        skipmask |= 1<<n;
                                        }
                                else
                                        for (n = 1 << st->ndim; n--; ) {
                                                if (!(n & 1<<i))
                                                        skipmask |= 1<<n;
                                        }
                        }
                for (n = 1 << st->ndim; n--; ) {
                        if (1<<n & skipmask)
                                continue;
                        for (i = st->ndim; i--; )
                                if (1<<i & n)
                                        bmin[i] = cmin[i] + csiz;
                                else
                                        bmin[i] = cmin[i];

                        rval += rv = SDdotravTre(st->u.t[n], pos, cmask,
                                                        cf, cptr, bmin, csiz);
                        if (rv < 0)
                                return rv;
                }
        } else {                        /* else traverse leaves */
                int     clim[SD_MAXDIM][2];
                int     cpos[SD_MAXDIM];

                if (st->log2GR == 0)    /* short cut */
                        return (*cf)(st->u.v[0], cmin, csiz, cptr);

                csiz /= (double)(1 << st->log2GR);
                                        /* assign coord. ranges */
                for (i = st->ndim; i--; )
                        if (1<<i & cmask) {
                                clim[i][0] = (pos[i] - cmin[i])/csiz;
                                        /* check overflow from f.p. error */
                                clim[i][0] -= clim[i][0] >> st->log2GR;
                                clim[i][1] = clim[i][0] + 1;
                        } else {
                                clim[i][0] = 0;
                                clim[i][1] = 1 << st->log2GR;
                        }
#if (SD_MAXDIM == 4)
                bmin[0] = cmin[0] + csiz*clim[0][0];
                for (cpos[0] = clim[0][0]; cpos[0] < clim[0][1]; cpos[0]++) {
                    bmin[1] = cmin[1] + csiz*clim[1][0];
                    for (cpos[1] = clim[1][0]; cpos[1] < clim[1][1]; cpos[1]++) {
                        bmin[2] = cmin[2] + csiz*clim[2][0];
                        if (st->ndim == 3) {
                            cpos[2] = clim[2][0];
                            n = cpos[0];
                            for (i = 1; i < 3; i++)
                                n = (n << st->log2GR) + cpos[i];
                            for ( ; cpos[2] < clim[2][1]; cpos[2]++) {
                                rval += rv = (*cf)(st->u.v[n++], bmin, csiz, cptr);
                                if (rv < 0)
                                    return rv;
                                bmin[2] += csiz;
                            }
                        } else {
                            for (cpos[2] = clim[2][0]; cpos[2] < clim[2][1]; cpos[2]++) {
                                bmin[3] = cmin[3] + csiz*(cpos[3] = clim[3][0]);
                                n = cpos[0];
                                for (i = 1; i < 4; i++)
                                    n = (n << st->log2GR) + cpos[i];
                                for ( ; cpos[3] < clim[3][1]; cpos[3]++) {
                                    rval += rv = (*cf)(st->u.v[n++], bmin, csiz, cptr);
                                    if (rv < 0)
                                        return rv;
                                    bmin[3] += csiz;
                                }
                                bmin[2] += csiz;
                            }
                        }
                        bmin[1] += csiz;
                    }
                    bmin[0] += csiz;
                }
#else
        _!_ "broken code segment!"
#endif
        }
        return rval;
}

/* Traverse a tree, visiting nodes in a slice that fits partial position */
static int
SDtraverseTre(const SDNode *st, const double *pos, int cmask,
                                SDtreCallback *cf, void *cptr)
{
        int             i;
                                        /* check arguments */
        if ((st == NULL) | (cf == NULL))
                return -1;
        for (i = st->ndim; i--; )
                if (1<<i & cmask && (pos[i] < 0) | (pos[i] >= 1.))
                        return -1;

        return SDdotravTre(st, pos, cmask, cf, cptr, czero, 1.);
}

/* Look up tree value at the given grid position */
static float
SDlookupTre(const SDNode *st, const double *pos, double *hcube)
{
        double  spos[SD_MAXDIM];
        int     i, n, t;
                                        /* initialize voxel return */
        if (hcube) {
                hcube[i = st->ndim] = 1.;
                while (i--)
                        hcube[i] = .0;
        }
                                        /* climb the tree */
        while (st != NULL && st->log2GR < 0) {
                n = 0;                  /* move to appropriate branch */
                if (hcube) hcube[st->ndim] *= .5;
                for (i = st->ndim; i--; ) {
                        spos[i] = 2.*pos[i];
                        t = (spos[i] >= 1.);
                        n |= t<<i;
                        spos[i] -= (double)t;
                        if (hcube) hcube[i] += (double)t * hcube[st->ndim];
                }
                st = st->u.t[n];        /* avoids tail recursion */
                pos = spos;
        }
        if (st == NULL)                 /* should never happen? */
                return .0;
        if (st->log2GR == 0)            /* short cut */
                return st->u.v[0];
        n = t = 0;                      /* find grid array index */
        for (i = st->ndim; i--; ) {
                n += (int)((1<<st->log2GR)*pos[i]) << t;
                t += st->log2GR;
        }
        if (hcube) {                    /* compute final hypercube */
                hcube[st->ndim] /= (double)(1<<st->log2GR);
                for (i = st->ndim; i--; )
                        hcube[i] += floor((1<<st->log2GR)*pos[i])*hcube[st->ndim];
        }
        return st->u.v[n];              /* no interpolation */
}

/* Convert CIE (Y,u',v') color to our RGB */
static void
SDyuv2rgb(double yval, double uprime, double vprime, float rgb[3])
{
        const double    dfact = 1./(6.*uprime - 16.*vprime + 12.);
        C_COLOR         cxy;

        c_cset(&cxy, 9.*uprime*dfact, 4.*vprime*dfact);
        c_toSharpRGB(&cxy, yval, rgb);
}

static double
pfrac(double x)
{
        return( x - (int)x );
}

/* Query BSDF value and sample hypercube for the given vectors */
static int
SDqueryTre(const SDTre *sdt, float *coef,
                const FVECT inVec, const FVECT outVec, double *hc)
{
        const RREAL     *vtmp;
        double          hcube[SD_MAXDIM+1];
        float           yval;
        FVECT           rOutVec;
        RREAL           gridPos[4];
        double          d;
        int             i;

        if (sdt->stc[tt_Y] == NULL)     /* paranoia, I hope */
                return 0;

        switch (sdt->sidef) {           /* whose side are you on? */
        case SD_FREFL:
                if ((outVec[2] < 0) | (inVec[2] < 0))
                        return 0;
                break;
        case SD_BREFL:
                if ((outVec[2] > 0) | (inVec[2] > 0))
                        return 0;
                break;
        case SD_FXMIT:
                if (outVec[2] > 0) {
                        if (inVec[2] > 0)
                                return 0;
                        vtmp = outVec; outVec = inVec; inVec = vtmp;
                } else if (inVec[2] < 0)
                        return 0;
                break;
        case SD_BXMIT:
                if (inVec[2] > 0) {
                        if (outVec[2] > 0)
                                return 0;
                        vtmp = outVec; outVec = inVec; inVec = vtmp;
                } else if (outVec[2] < 0)
                        return 0;
                break;
        default:
                return 0;
        }
                                        /* convert vector coordinates */
        if (sdt->stc[tt_Y]->ndim == 3) {
                spinvector(rOutVec, outVec, zvec, -atan2(-inVec[1],-inVec[0]));
                gridPos[0] = (.5-FTINY) -
                                .5*sqrt(inVec[0]*inVec[0] + inVec[1]*inVec[1]);
                disk2square(gridPos+1, rOutVec[0], rOutVec[1]);
        } else if (sdt->stc[tt_Y]->ndim == 4) {
                disk2square(gridPos, -inVec[0], -inVec[1]);
                disk2square(gridPos+2, outVec[0], outVec[1]);
        } else
                return 0;               /* should be internal error */

        if (hc == NULL) hc = hcube;     /* get BSDF value */
        yval = SDlookupTre(sdt->stc[tt_Y], gridPos, hc);
        if (coef == NULL)               /* just getting hypercube? */
                return 1;
        d = 0;                          /* position-specific perturbation */
        for (i = sdt->stc[tt_Y]->ndim; i--; )
                d += pfrac((2<<i)/(hc[i]+.01687)) - .5;
        yval *= 1. + 1e-4*d;            /* assumes tolerance is > 0.04% */
        if (sdt->stc[tt_u] == NULL || sdt->stc[tt_v] == NULL) {
                *coef = yval;
                return 1;               /* no color */
        }
                                        /* else decode color */
        SDyuv2rgb(yval, SDlookupTre(sdt->stc[tt_u], gridPos, NULL),
                        SDlookupTre(sdt->stc[tt_v], gridPos, NULL), coef);
        coef[0] *= tt_RGB_coef[0];
        coef[1] *= tt_RGB_coef[1];
        coef[2] *= tt_RGB_coef[2];
        return 3;
}

/* Compute non-diffuse component for variable-resolution BSDF */
static int
SDgetTreBSDF(float coef[SDmaxCh], const FVECT outVec,
                                const FVECT inVec, SDComponent *sdc)
{
                                        /* check arguments */
        if ((coef == NULL) | (outVec == NULL) | (inVec == NULL) | (sdc == NULL)
                                || sdc->dist == NULL)
                return 0;
                                        /* get nearest BSDF value */
        return SDqueryTre((SDTre *)sdc->dist, coef, outVec, inVec, NULL);
}

/* Callback to build cumulative distribution using SDtraverseTre() */
static int
build_scaffold(float val, const double *cmin, double csiz, void *cptr)
{
        SDdistScaffold  *sp = (SDdistScaffold *)cptr;
        int             wid = csiz*(double)iwmax + .5;
        double          revcmin[2];
        bitmask_t       bmin[2], bmax[2];

        if (sp->rev) {                  /* need to reverse sense? */
                revcmin[0] = 1. - cmin[0] - csiz;
                revcmin[1] = 1. - cmin[1] - csiz;
                cmin = revcmin;
        } else {
                cmin += sp->nic;        /* else skip to output coords */
        }
        if (wid < sp->wmin)             /* new minimum width? */
                sp->wmin = wid;
        if (wid > sp->wmax)             /* new maximum? */
                sp->wmax = wid;
        if (sp->alen >= sp->nall) {     /* need more space? */
                struct outdir_s *ndarr;
                sp->nall = (int)(1.5*sp->nall) + 256;
                ndarr = (struct outdir_s *)realloc(sp->darr,
                                        sizeof(struct outdir_s)*sp->nall);
                if (ndarr == NULL) {
                        sprintf(SDerrorDetail,
                                "Cannot grow scaffold to %u entries", sp->nall);
                        return -1;      /* abort build */
                }
                sp->darr = ndarr;
        }
                                        /* find Hilbert entry index */
        bmin[0] = cmin[0]*(double)iwmax + .5;
        bmin[1] = cmin[1]*(double)iwmax + .5;
        bmax[0] = bmin[0] + wid-1;
        bmax[1] = bmin[1] + wid-1;
        hilbert_box_vtx(2, sizeof(bitmask_t), iwbits, 1, bmin, bmax);
        sp->darr[sp->alen].hent = hilbert_c2i(2, iwbits, bmin);
        sp->darr[sp->alen].wid = wid;
        sp->darr[sp->alen].bsdf = val;
        sp->alen++;                     /* on to the next entry */
        return 0;
}

/* Scaffold comparison function for qsort -- ascending Hilbert index */
static int
sscmp(const void *p1, const void *p2)
{
        unsigned        h1 = (*(const struct outdir_s *)p1).hent;
        unsigned        h2 = (*(const struct outdir_s *)p2).hent;

        if (h1 > h2)
                return 1;
        if (h1 < h2)
                return -1;
        return 0;
}

/* Create a new cumulative distribution for the given input direction */
static SDTreCDst *
make_cdist(const SDTre *sdt, const double *invec, int rev)
{
        SDdistScaffold  myScaffold;
        double          pos[4];
        int             cmask;
        SDTreCDst       *cd;
        struct outdir_s *sp;
        double          scale, cursum;
        int             i;
                                        /* initialize scaffold */
        myScaffold.wmin = iwmax;
        myScaffold.wmax = 0;
        myScaffold.nic = sdt->stc[tt_Y]->ndim - 2;
        myScaffold.rev = rev;
        myScaffold.alen = 0;
        myScaffold.nall = 512;
        myScaffold.darr = (struct outdir_s *)malloc(sizeof(struct outdir_s) *
                                                        myScaffold.nall);
        if (myScaffold.darr == NULL)
                return NULL;
                                        /* set up traversal */
        cmask = (1<<myScaffold.nic) - 1;
        for (i = myScaffold.nic; i--; )
                        pos[i+2*rev] = invec[i];
        cmask <<= 2*rev;
                                        /* grow the distribution */
        if (SDtraverseTre(sdt->stc[tt_Y], pos, cmask,
                                build_scaffold, &myScaffold) < 0) {
                free(myScaffold.darr);
                return NULL;
        }
                                        /* allocate result holder */
        cd = (SDTreCDst *)malloc(sizeof(SDTreCDst) +
                                sizeof(cd->carr[0])*myScaffold.alen);
        if (cd == NULL) {
                sprintf(SDerrorDetail,
                        "Cannot allocate %u entry cumulative distribution",
                                myScaffold.alen);
                free(myScaffold.darr);
                return NULL;
        }
        cd->isodist = (myScaffold.nic == 1);
                                        /* sort the distribution */
        qsort(myScaffold.darr, cd->calen = myScaffold.alen,
                                sizeof(struct outdir_s), sscmp);

                                        /* record input range */
        scale = myScaffold.wmin / (double)iwmax;
        for (i = myScaffold.nic; i--; ) {
                cd->clim[i][0] = floor(pos[i+2*rev]/scale) * scale;
                cd->clim[i][1] = cd->clim[i][0] + scale;
        }
        if (cd->isodist) {              /* avoid issue in SDqueryTreProjSA() */
                cd->clim[1][0] = cd->clim[0][0];
                cd->clim[1][1] = cd->clim[0][1];
        }
        cd->max_psa = myScaffold.wmax / (double)iwmax;
        cd->max_psa *= cd->max_psa * M_PI;
        if (rev)
                cd->sidef = (sdt->sidef==SD_BXMIT) ? SD_FXMIT : SD_BXMIT;
        else
                cd->sidef = sdt->sidef;
        cd->cTotal = 1e-20;             /* compute directional total */
        sp = myScaffold.darr;
        for (i = myScaffold.alen; i--; sp++)
                cd->cTotal += sp->bsdf * (double)sp->wid * sp->wid;
        cursum = .0;                    /* go back and get cumulative values */
        scale = (double)cumlmax / cd->cTotal;
        sp = myScaffold.darr;
        for (i = 0; i < cd->calen; i++, sp++) {
                cd->carr[i].hndx = sp->hent;
                cd->carr[i].cuml = scale*cursum + .5;
                cursum += sp->bsdf * (double)sp->wid * sp->wid;
        }
        cd->carr[i].hndx = ~0;          /* make final entry */
        cd->carr[i].cuml = cumlmax;
        cd->cTotal *= M_PI/(double)iwmax/iwmax;
                                        /* all done, clean up and return */
        free(myScaffold.darr);
        return cd;
}

/* Find or allocate a cumulative distribution for the given incoming vector */
const SDCDst *
SDgetTreCDist(const FVECT inVec, SDComponent *sdc)
{
        unsigned long   cacheLeft = SDmaxCache;
        const SDTre     *sdt;
        RREAL           inCoord[2];
        int             i;
        int             mode;
        SDTreCDst       *cd, *cdlast, *cdlimit;
                                        /* check arguments */
        if ((inVec == NULL) | (sdc == NULL) ||
                        (sdt = (SDTre *)sdc->dist) == NULL)
                return NULL;
        switch (mode = sdt->sidef) {    /* check direction */
        case SD_FREFL:
                if (inVec[2] < 0)
                        return NULL;
                break;
        case SD_BREFL:
                if (inVec[2] > 0)
                        return NULL;
                break;
        case SD_FXMIT:
                if (inVec[2] < 0)
                        mode = SD_BXMIT;
                break;
        case SD_BXMIT:
                if (inVec[2] > 0)
                        mode = SD_FXMIT;
                break;
        default:
                return NULL;
        }
        if (sdt->stc[tt_Y]->ndim == 3) {        /* isotropic BSDF? */
                if (mode != sdt->sidef) /* XXX unhandled reciprocity */
                        return &SDemptyCD;
                inCoord[0] = (.5-FTINY) -
                                .5*sqrt(inVec[0]*inVec[0] + inVec[1]*inVec[1]);
        } else if (sdt->stc[tt_Y]->ndim == 4) {
                if (mode != sdt->sidef) /* use reciprocity? */
                        disk2square(inCoord, inVec[0], inVec[1]);
                else
                        disk2square(inCoord, -inVec[0], -inVec[1]);
        } else
                return NULL;            /* should be internal error */
                                        /* quantize to avoid f.p. errors */
        for (i = sdt->stc[tt_Y]->ndim - 2; i--; )
                inCoord[i] = floor(inCoord[i]/quantum)*quantum + .5*quantum;
        cdlast = cdlimit = NULL;        /* check for direction in cache list */
        /* PLACE MUTEX LOCK HERE FOR THREAD-SAFE */
        for (cd = (SDTreCDst *)sdc->cdList; cd != NULL;
                                        cdlast = cd, cd = cd->next) {
                if (cacheLeft) {        /* check cache size limit */
                        long    csiz = sizeof(SDTreCDst) +
                                        sizeof(cd->carr[0])*cd->calen;
                        if (cacheLeft > csiz)
                                cacheLeft -= csiz;
                        else {
                                cdlimit = cdlast;
                                cacheLeft = 0;
                        }
                }
                if (cd->sidef != mode)
                        continue;
                for (i = sdt->stc[tt_Y]->ndim - 2; i--; )
                        if ((cd->clim[i][0] > inCoord[i]) |
                                        (inCoord[i] >= cd->clim[i][1]))
                                break;
                if (i < 0)
                        break;          /* means we have a match */
        }
        if (cd == NULL) {               /* need to create new entry? */
                if (cdlimit != NULL)    /* exceeded cache size limit? */
                        while ((cd = cdlimit->next) != NULL) {
                                cdlimit->next = cd->next;
                                free(cd);
                        }
                cdlast = cd = make_cdist(sdt, inCoord, mode != sdt->sidef);
        }
        if (cdlast != NULL) {           /* move entry to head of cache list */
                cdlast->next = cd->next;
                cd->next = (SDTreCDst *)sdc->cdList;
                sdc->cdList = (SDCDst *)cd;
        }
        /* END MUTEX LOCK */
        return (SDCDst *)cd;            /* ready to go */
}

/* Query solid angle for vector(s) */
static SDError
SDqueryTreProjSA(double *psa, const FVECT v1, const RREAL *v2,
                                        int qflags, SDComponent *sdc)
{
        double          myPSA[2];
                                        /* check arguments */
        if ((psa == NULL) | (v1 == NULL) | (sdc == NULL) ||
                                sdc->dist == NULL)
                return SDEargument;
                                        /* get projected solid angle(s) */
        if (v2 != NULL) {
                const SDTre     *sdt = (SDTre *)sdc->dist;
                double          hcube[SD_MAXDIM+1];
                if (!SDqueryTre(sdt, NULL, v1, v2, hcube)) {
                        strcpy(SDerrorDetail, "Bad call to SDqueryTreProjSA");
                        return SDEinternal;
                }
                myPSA[0] = hcube[sdt->stc[tt_Y]->ndim];
                myPSA[1] = myPSA[0] *= myPSA[0] * M_PI;
        } else {
                const SDTreCDst *cd = (const SDTreCDst *)SDgetTreCDist(v1, sdc);
                if (cd == NULL)
                        myPSA[0] = myPSA[1] = 0;
                else {
                        myPSA[0] = M_PI * (cd->clim[0][1] - cd->clim[0][0]) *
                                        (cd->clim[1][1] - cd->clim[1][0]);
                        myPSA[1] = cd->max_psa;
                }
        }
        switch (qflags) {               /* record based on flag settings */
        case SDqueryVal:
                *psa = myPSA[0];
                break;
        case SDqueryMax:
                if (myPSA[1] > *psa)
                        *psa = myPSA[1];
                break;
        case SDqueryMin+SDqueryMax:
                if (myPSA[1] > psa[1])
                        psa[1] = myPSA[1];
                /* fall through */
        case SDqueryMin:
                if ((myPSA[0] > 0) & (myPSA[0] < psa[0]))
                        psa[0] = myPSA[0];
                break;
        }
        return SDEnone;
}

/* Sample cumulative distribution */
static SDError
SDsampTreCDist(FVECT ioVec, double randX, const SDCDst *cdp)
{
        const unsigned  nBitsC = 4*sizeof(bitmask_t);
        const unsigned  nExtraBits = 8*(sizeof(bitmask_t)-sizeof(unsigned));
        const SDTreCDst *cd = (const SDTreCDst *)cdp;
        const unsigned  target = randX*cumlmax;
        bitmask_t       hndx, hcoord[2];
        FVECT           gpos;
        double          rotangle;
        int             i, iupper, ilower;
                                        /* check arguments */
        if ((ioVec == NULL) | (cd == NULL))
                return SDEargument;
        if (!cd->sidef)
                return SDEnone;         /* XXX should never happen */
        if (ioVec[2] > 0) {
                if ((cd->sidef != SD_FREFL) & (cd->sidef != SD_FXMIT))
                        return SDEargument;
        } else if ((cd->sidef != SD_BREFL) & (cd->sidef != SD_BXMIT))
                return SDEargument;
                                        /* binary search to find position */
        ilower = 0; iupper = cd->calen;
        while ((i = (iupper + ilower) >> 1) != ilower)
                if (target >= cd->carr[i].cuml)
                        ilower = i;
                else
                        iupper = i;
                                        /* localize random position */
        randX = (randX*cumlmax - cd->carr[ilower].cuml) /
                    (double)(cd->carr[iupper].cuml - cd->carr[ilower].cuml);
                                        /* index in longer Hilbert curve */
        hndx = (randX*cd->carr[iupper].hndx + (1.-randX)*cd->carr[ilower].hndx)
                                * (double)((bitmask_t)1 << nExtraBits);
                                        /* convert Hilbert index to vector */
        hilbert_i2c(2, nBitsC, hndx, hcoord);
        for (i = 2; i--; )
                gpos[i] = ((double)hcoord[i] + rand()*(1./(RAND_MAX+.5))) /
                                (double)((bitmask_t)1 << nBitsC);
        square2disk(gpos, gpos[0], gpos[1]);
                                        /* compute Z-coordinate */
        gpos[2] = 1. - gpos[0]*gpos[0] - gpos[1]*gpos[1];
        gpos[2] = sqrt(gpos[2]*(gpos[2]>0));
                                        /* emit from back? */
        if ((cd->sidef == SD_BREFL) | (cd->sidef == SD_FXMIT))
                gpos[2] = -gpos[2];
        if (cd->isodist) {              /* rotate isotropic sample */
                rotangle = atan2(-ioVec[1],-ioVec[0]);
                spinvector(ioVec, gpos, zvec, rotangle);
        } else
                VCOPY(ioVec, gpos);
        return SDEnone;
}

/* Advance pointer to the next non-white character in the string (or nul) */
static int
next_token(char **spp)
{
        while (isspace(**spp))
                ++*spp;
        return **spp;
}

/* Advance pointer past matching token (or any token if c==0) */
#define eat_token(spp,c)        ((next_token(spp)==(c)) ^ !(c) ? *(*(spp))++ : 0)

/* Count words from this point in string to '}' */
static int
count_values(char *cp)
{
        int     n = 0;

        while (next_token(&cp) != '}' && *cp) {
                while (!isspace(*cp) & (*cp != ',') & (*cp != '}'))
                        if (!*++cp)
                                break;
                ++n;
                eat_token(&cp, ',');
        }
        return n;
}

/* Load an array of real numbers, returning total */
static int
load_values(char **spp, float *va, int n)
{
        float   *v = va;
        char    *svnext;

        while (n-- > 0 && (svnext = fskip(*spp)) != NULL) {
                if ((*v++ = atof(*spp)) < 0)
                        v[-1] = 0;
                *spp = svnext;
                eat_token(spp, ',');
        }
        return v - va;
}

/* Load BSDF tree data */
static SDNode *
load_tree_data(char **spp, int nd)
{
        SDNode  *st;
        int     n;

        if (!eat_token(spp, '{')) {
                strcpy(SDerrorDetail, "Missing '{' in tensor tree");
                return NULL;
        }
        if (next_token(spp) == '{') {   /* tree branches */
                st = SDnewNode(nd, -1);
                if (st == NULL)
                        return NULL;
                for (n = 0; n < 1<<nd; n++)
                        if ((st->u.t[n] = load_tree_data(spp, nd)) == NULL) {
                                SDfreeTre(st);
                                return NULL;
                        }
        } else {                        /* else load value grid */
                int     bsiz;
                n = count_values(*spp); /* see how big the grid is */
                for (bsiz = 0; bsiz < 8*sizeof(size_t); bsiz += nd)
                        if (1<<bsiz == n)
                                break;
                if (bsiz >= 8*sizeof(size_t)) {
                        strcpy(SDerrorDetail, "Illegal value count in tensor tree");
                        return NULL;
                }
                st = SDnewNode(nd, bsiz/nd);
                if (st == NULL)
                        return NULL;
                if (load_values(spp, st->u.v, n) != n) {
                        strcpy(SDerrorDetail, "Real format error in tensor tree");
                        SDfreeTre(st);
                        return NULL;
                }
        }
        if (!eat_token(spp, '}')) {
                strcpy(SDerrorDetail, "Missing '}' in tensor tree");
                SDfreeTre(st);
                return NULL;
        }
        eat_token(spp, ',');
        return st;
}

/* Compute min. proj. solid angle and max. direct hemispherical scattering */
static SDError
get_extrema(SDSpectralDF *df)
{
        SDNode  *st = (*(SDTre *)df->comp[0].dist).stc[tt_Y];
        double  stepWidth, dhemi, bmin[4], bmax[4];

        stepWidth = SDsmallestLeaf(st);
        if (quantum > stepWidth)        /* adjust quantization factor */
                quantum = stepWidth;
        df->minProjSA = M_PI*stepWidth*stepWidth;
        if (stepWidth < .03125)
                stepWidth = .03125;     /* 1/32 resolution good enough */
        df->maxHemi = .0;
        if (st->ndim == 3) {            /* isotropic BSDF */
                bmin[1] = bmin[2] = .0;
                bmax[1] = bmax[2] = 1.;
                for (bmin[0] = .0; bmin[0] < .5-FTINY; bmin[0] += stepWidth) {
                        bmax[0] = bmin[0] + stepWidth;
                        dhemi = SDavgTreBox(st, bmin, bmax);
                        if (dhemi > df->maxHemi)
                                df->maxHemi = dhemi;
                }
        } else if (st->ndim == 4) {     /* anisotropic BSDF */
                bmin[2] = bmin[3] = .0;
                bmax[2] = bmax[3] = 1.;
                for (bmin[0] = .0; bmin[0] < 1.-FTINY; bmin[0] += stepWidth) {
                        bmax[0] = bmin[0] + stepWidth;
                        for (bmin[1] = .0; bmin[1] < 1.-FTINY; bmin[1] += stepWidth) {
                                bmax[1] = bmin[1] + stepWidth;
                                dhemi = SDavgTreBox(st, bmin, bmax);
                                if (dhemi > df->maxHemi)
                                        df->maxHemi = dhemi;
                        }
                }
        } else
                return SDEinternal;
                                        /* correct hemispherical value */
        df->maxHemi *= M_PI;
        return SDEnone;
}

/* Load BSDF distribution for this wavelength */
static SDError
load_bsdf_data(SDData *sd, ezxml_t wdb, int ct, int ndim)
{
        SDSpectralDF    *df;
        SDTre           *sdt;
        char            *sdata;
                                        /* allocate BSDF component */
        sdata = ezxml_txt(ezxml_child(wdb, "WavelengthDataDirection"));
        if (!sdata)
                return SDEnone;
        /*
         * Remember that front and back are reversed from WINDOW 6 orientations
         */
        if (!strcasecmp(sdata, "Transmission Front")) {
                if (sd->tb == NULL && (sd->tb = SDnewSpectralDF(1)) == NULL)
                        return SDEmemory;
                df = sd->tb;
        } else if (!strcasecmp(sdata, "Transmission Back")) {
                if (sd->tf == NULL && (sd->tf = SDnewSpectralDF(1)) == NULL)
                        return SDEmemory;
                df = sd->tf;
        } else if (!strcasecmp(sdata, "Reflection Front")) {
                if (sd->rb == NULL && (sd->rb = SDnewSpectralDF(1)) == NULL)
                        return SDEmemory;
                df = sd->rb;
        } else if (!strcasecmp(sdata, "Reflection Back")) {
                if (sd->rf == NULL && (sd->rf = SDnewSpectralDF(1)) == NULL)
                        return SDEmemory;
                df = sd->rf;
        } else
                return SDEnone;
                                        /* get angle bases */
        sdata = ezxml_txt(ezxml_child(wdb,"AngleBasis"));
        if (!sdata || strcasecmp(sdata, "LBNL/Shirley-Chiu")) {
                sprintf(SDerrorDetail, "%s angle basis for BSDF '%s'",
                                !sdata ? "Missing" : "Unsupported", sd->name);
                return !sdata ? SDEformat : SDEsupport;
        }
        if (df->comp[0].dist == NULL) { /* need to allocate BSDF tree? */
                sdt = (SDTre *)malloc(sizeof(SDTre));
                if (sdt == NULL)
                        return SDEmemory;
                if (df == sd->rf)
                        sdt->sidef = SD_FREFL;
                else if (df == sd->rb)
                        sdt->sidef = SD_BREFL;
                else if (df == sd->tf)
                        sdt->sidef = SD_FXMIT;
                else /* df == sd->tb */
                        sdt->sidef = SD_BXMIT;
                sdt->stc[tt_Y] = sdt->stc[tt_u] = sdt->stc[tt_v] = NULL;
                df->comp[0].dist = sdt;
                df->comp[0].func = &SDhandleTre;
        } else {
                sdt = (SDTre *)df->comp[0].dist;
                if (sdt->stc[ct] != NULL) {
                        SDfreeTre(sdt->stc[ct]);
                        sdt->stc[ct] = NULL;
                }
        }
                                        /* read BSDF data */
        sdata = ezxml_txt(ezxml_child(wdb, "ScatteringData"));
        if (!sdata || !next_token(&sdata)) {
                sprintf(SDerrorDetail, "Missing BSDF ScatteringData in '%s'",
                                sd->name);
                return SDEformat;
        }
        sdt->stc[ct] = load_tree_data(&sdata, ndim);
        if (sdt->stc[ct] == NULL)
                return SDEformat;
        if (next_token(&sdata)) {       /* check for unconsumed characters */
                sprintf(SDerrorDetail,
                        "Extra characters at end of ScatteringData in '%s'",
                                sd->name);
                return SDEformat;
        }
                                        /* flatten branches where possible */
        sdt->stc[ct] = SDsimplifyTre(sdt->stc[ct]);
        if (sdt->stc[ct] == NULL)
                return SDEinternal;
                                        /* compute global quantities for Y */
        return (ct == tt_Y) ? get_extrema(df) : SDEnone;
}

/* Find minimum value in tree */
static float
SDgetTreMin(const SDNode *st)
{
        float   vmin = FHUGE;
        int     n;

        if (st->log2GR < 0) {
                for (n = 1<<st->ndim; n--; ) {
                        float   v = SDgetTreMin(st->u.t[n]);
                        if (v < vmin)
                                vmin = v;
                }
        } else {
                for (n = 1<<(st->ndim*st->log2GR); n--; )
                        if (st->u.v[n] < vmin)
                                vmin = st->u.v[n];
        }
        return vmin;
}

/* Subtract the given value from all tree nodes */
static void
SDsubtractTreVal(SDNode *st, float val)
{
        int     n;

        if (st->log2GR < 0) {
                for (n = 1<<st->ndim; n--; )
                        SDsubtractTreVal(st->u.t[n], val);
        } else {
                for (n = 1<<(st->ndim*st->log2GR); n--; )
                        if ((st->u.v[n] -= val) < 0)
                                st->u.v[n] = .0f;
        }
}

/* Subtract minimum Y value from BSDF */
static double
subtract_min_Y(SDNode *st)
{
        const float     vmaxmin = 1.5/M_PI;
        float           vmin;
                                        /* be sure to skip unused portion */
        if (st->ndim == 3) {
                int     n;
                vmin = vmaxmin;
                if (st->log2GR < 0) {
                        for (n = 0; n < 8; n += 2) {
                                float   v = SDgetTreMin(st->u.t[n]);
                                if (v < vmin)
                                        vmin = v;
                        }
                } else if (st->log2GR) {
                        for (n = 1 << (3*st->log2GR - 1); n--; )
                                if (st->u.v[n] < vmin)
                                        vmin = st->u.v[n];
                } else
                        vmin = st->u.v[0];
        } else                          /* anisotropic covers entire tree */
                vmin = SDgetTreMin(st);

        if ((vmin >= vmaxmin) | (vmin <= .01/M_PI))
                return .0;              /* not worth bothering about */

        SDsubtractTreVal(st, vmin);

        return M_PI * vmin;             /* return hemispherical value */
}

/* Struct used in callback to find RGB extrema */
typedef struct {
        SDNode  **stc;                  /* original Y, u' & v' trees */
        float   rgb[3];                 /* RGB value */
        SDNode  *new_stu, *new_stv;     /* replacement u' & v' trees */
} SDextRGBs;

/* Callback to find minimum RGB from Y value plus CIE (u',v') trees */
static int
get_min_RGB(float yval, const double *cmin, double csiz, void *cptr)
{
        SDextRGBs       *mp = (SDextRGBs *)cptr;
        double          cmax[SD_MAXDIM];
        float           rgb[3];

        if (mp->stc[tt_Y]->ndim == 3) {
                if (cmin[0] + .5*csiz >= .5)
                        return 0;       /* ignore dead half of isotropic */
        } else
                cmax[3] = cmin[3] + csiz;
        cmax[0] = cmin[0] + csiz;
        cmax[1] = cmin[1] + csiz;
        cmax[2] = cmin[2] + csiz;
                                        /* average RGB color over voxel */
        SDyuv2rgb(yval, SDavgTreBox(mp->stc[tt_u], cmin, cmax),
                        SDavgTreBox(mp->stc[tt_v], cmin, cmax), rgb);
                                        /* track smallest components */
        if (rgb[0] < mp->rgb[0]) mp->rgb[0] = rgb[0];
        if (rgb[1] < mp->rgb[1]) mp->rgb[1] = rgb[1];
        if (rgb[2] < mp->rgb[2]) mp->rgb[2] = rgb[2];
        return 0;
}

/* Callback to build adjusted u' tree */
static int
adjust_utree(float uprime, const double *cmin, double csiz, void *cptr)
{
        SDextRGBs       *mp = (SDextRGBs *)cptr;
        double          cmax[SD_MAXDIM];
        double          yval;
        float           rgb[3];
        C_COLOR         clr;

        if (mp->stc[tt_Y]->ndim == 3) {
                if (cmin[0] + .5*csiz >= .5)
                        return 0;       /* ignore dead half of isotropic */
        } else
                cmax[3] = cmin[3] + csiz;
        cmax[0] = cmin[0] + csiz;
        cmax[1] = cmin[1] + csiz;
        cmax[2] = cmin[2] + csiz;
                                        /* average RGB color over voxel */
        SDyuv2rgb(yval=SDavgTreBox(mp->stc[tt_Y], cmin, cmax), uprime,
                        SDavgTreBox(mp->stc[tt_v], cmin, cmax), rgb);
                                        /* subtract minimum (& clamp) */
        if ((rgb[0] -= mp->rgb[0]) < 1e-5*yval) rgb[0] = 1e-5*yval;
        if ((rgb[1] -= mp->rgb[1]) < 1e-5*yval) rgb[1] = 1e-5*yval;
        if ((rgb[2] -= mp->rgb[2]) < 1e-5*yval) rgb[2] = 1e-5*yval;
        c_fromSharpRGB(rgb, &clr);      /* compute new u' for adj. RGB */
        uprime = 4.*clr.cx/(-2.*clr.cx + 12.*clr.cy + 3.);
                                        /* assign in new u' tree */
        mp->new_stu = SDsetVoxel(mp->new_stu, mp->stc[tt_Y]->ndim,
                                        cmin, csiz, uprime);
        return -(mp->new_stu == NULL);
}

/* Callback to build adjusted v' tree */
static int
adjust_vtree(float vprime, const double *cmin, double csiz, void *cptr)
{
        SDextRGBs       *mp = (SDextRGBs *)cptr;
        double          cmax[SD_MAXDIM];
        double          yval;
        float           rgb[3];
        C_COLOR         clr;

        if (mp->stc[tt_Y]->ndim == 3) {
                if (cmin[0] + .5*csiz >= .5)
                        return 0;       /* ignore dead half of isotropic */
        } else
                cmax[3] = cmin[3] + csiz;
        cmax[0] = cmin[0] + csiz;
        cmax[1] = cmin[1] + csiz;
        cmax[2] = cmin[2] + csiz;
                                        /* average RGB color over voxel */
        SDyuv2rgb(yval=SDavgTreBox(mp->stc[tt_Y], cmin, cmax),
                        SDavgTreBox(mp->stc[tt_u], cmin, cmax),
                        vprime, rgb);
                                        /* subtract minimum (& clamp) */
        if ((rgb[0] -= mp->rgb[0]) < 1e-5*yval) rgb[0] = 1e-5*yval;
        if ((rgb[1] -= mp->rgb[1]) < 1e-5*yval) rgb[1] = 1e-5*yval;
        if ((rgb[2] -= mp->rgb[2]) < 1e-5*yval) rgb[2] = 1e-5*yval;
        c_fromSharpRGB(rgb, &clr);      /* compute new v' for adj. RGB */
        vprime = 9.*clr.cy/(-2.*clr.cx + 12.*clr.cy + 3.);
                                        /* assign in new v' tree */
        mp->new_stv = SDsetVoxel(mp->new_stv, mp->stc[tt_Y]->ndim,
                                        cmin, csiz, vprime);
        return -(mp->new_stv == NULL);
}

/* Subtract minimum (diffuse) color and return luminance & CIE (x,y) */
static double
subtract_min_RGB(C_COLOR *cs, SDNode *stc[])
{
        SDextRGBs       my_min;
        double          ymin;

        my_min.stc = stc;
        my_min.rgb[0] = my_min.rgb[1] = my_min.rgb[2] = FHUGE;
        my_min.new_stu = my_min.new_stv = NULL;
                                        /* get minimum RGB value */
        SDtraverseTre(stc[tt_Y], NULL, 0, get_min_RGB, &my_min);
                                        /* convert to C_COLOR */
        ymin =  c_fromSharpRGB(my_min.rgb, cs);
        if ((ymin >= .5*FHUGE) | (ymin <= .01/M_PI))
                return .0;              /* close to zero or no tree */
                                        /* adjust u' & v' trees */
        SDtraverseTre(stc[tt_u], NULL, 0, adjust_utree, &my_min);
        SDtraverseTre(stc[tt_v], NULL, 0, adjust_vtree, &my_min);
        SDfreeTre(stc[tt_u]); SDfreeTre(stc[tt_v]);
        stc[tt_u] = SDsimplifyTre(my_min.new_stu);
        stc[tt_v] = SDsimplifyTre(my_min.new_stv);
                                        /* subtract Y & return hemispherical */
        SDsubtractTreVal(stc[tt_Y], ymin);

        return M_PI * ymin;
}

/* Extract and separate diffuse portion of BSDF */
static void
extract_diffuse(SDValue *dv, SDSpectralDF *df)
{
        int     n;
        SDTre   *sdt;

        if (df == NULL || df->ncomp <= 0) {
                dv->spec = c_dfcolor;
                dv->cieY = .0;
                return;
        }
        sdt = (SDTre *)df->comp[0].dist;
                                        /* subtract minimum color/grayscale */
        if (sdt->stc[tt_u] != NULL && sdt->stc[tt_v] != NULL) {
                int     i = 3*(tt_RGB_coef[1] < .001);
                while (i--) {           /* initialize on first call */
                        float   rgb[3];
                        rgb[0] = rgb[1] = rgb[2] = .0f; rgb[i] = 1.f;
                        tt_RGB_coef[i] = c_fromSharpRGB(rgb, &tt_RGB_prim[i]);
                }
                memcpy(df->comp[0].cspec, tt_RGB_prim, sizeof(tt_RGB_prim));
                dv->cieY = subtract_min_RGB(&dv->spec, sdt->stc);
        } else {
                df->comp[0].cspec[0] = dv->spec = c_dfcolor;
                dv->cieY = subtract_min_Y(sdt->stc[tt_Y]);
        }
        df->maxHemi -= dv->cieY;        /* adjust maximum hemispherical */
                                
        c_ccvt(&dv->spec, C_CSXY);      /* make sure (x,y) is set */
}

/* Load a variable-resolution BSDF tree from an open XML file */
SDError
SDloadTre(SDData *sd, ezxml_t wtl)
{
        SDError         ec;
        ezxml_t         wld, wdb;
        int             rank;
        char            *txt;
                                        /* basic checks and tensor rank */
        txt = ezxml_txt(ezxml_child(ezxml_child(wtl,
                        "DataDefinition"), "IncidentDataStructure"));
        if (txt == NULL || !*txt) {
                sprintf(SDerrorDetail,
                        "BSDF \"%s\": missing IncidentDataStructure",
                                sd->name);
                return SDEformat;
        }
        if (!strcasecmp(txt, "TensorTree3"))
                rank = 3;
        else if (!strcasecmp(txt, "TensorTree4"))
                rank = 4;
        else {
                sprintf(SDerrorDetail,
                        "BSDF \"%s\": unsupported IncidentDataStructure",
                                sd->name);
                return SDEsupport;
        }
                                        /* load BSDF components */
        for (wld = ezxml_child(wtl, "WavelengthData");
                                wld != NULL; wld = wld->next) {
                const char      *cnm = ezxml_txt(ezxml_child(wld,"Wavelength"));
                int             ct = -1;
                if (!strcasecmp(cnm, "Visible"))
                        ct = tt_Y;
                else if (!strcasecmp(cnm, "CIE-u"))
                        ct = tt_u;
                else if (!strcasecmp(cnm, "CIE-v"))
                        ct = tt_v;
                else
                        continue;
                for (wdb = ezxml_child(wld, "WavelengthDataBlock");
                                        wdb != NULL; wdb = wdb->next)
                        if ((ec = load_bsdf_data(sd, wdb, ct, rank)) != SDEnone)
                                return ec;
        }
                                        /* separate diffuse components */
        extract_diffuse(&sd->rLambFront, sd->rf);
        extract_diffuse(&sd->rLambBack, sd->rb);
        extract_diffuse(&sd->tLambFront, sd->tf);
        if (sd->tb != NULL) {
                extract_diffuse(&sd->tLambBack, sd->tb);
                if (sd->tf == NULL)
                        sd->tLambFront = sd->tLambBack;
        } else if (sd->tf != NULL)
                sd->tLambBack = sd->tLambFront;
                                        /* return success */
        return SDEnone;
}

/* Variable resolution BSDF methods */
const SDFunc SDhandleTre = {
        &SDgetTreBSDF,
        &SDqueryTreProjSA,
        &SDgetTreCDist,
        &SDsampTreCDist,
        &SDFreeBTre,
};
Revision:	3.54
Committed:	Tue Jan 25 01:34:20 2022 UTC (2 years, 3 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad5R4, HEAD
Changes since 3.53:	+16 -2 lines
Log Message:	fix: added position-based BSDF value perturbation for reliable peak extraction