src/common/bsdf.c

#ifndef lint
static const char RCSid[] = "$Id: bsdf.c,v 2.60 2021/04/28 00:59:10 greg Exp $";
#endif
/*
 *  bsdf.c
 *  
 *  Definitions for bidirectional scattering distribution functions.
 *
 *  Created by Greg Ward on 1/10/11.
 *
 */

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

/* English ASCII strings corresponding to ennumerated errors */
const char              *SDerrorEnglish[] = {
                                "No error",
                                "Memory error",
                                "File input/output error",
                                "File format error",
                                "Illegal argument",
                                "Invalid data",
                                "Unsupported feature",
                                "Internal program error",
                                "Unknown error"
                        };

/* Pointer to error list in preferred language */
const char              **SDerrorList = SDerrorEnglish;

/* Additional information on last error (ASCII English) */
char                    SDerrorDetail[256];

/* Empty distribution for getCDist() calls that fail for some reason */
const SDCDst            SDemptyCD;

/* Cache of loaded BSDFs */
struct SDCache_s        *SDcacheList = NULL;

/* Retain BSDFs in cache list? */
int                     SDretainSet = SDretainNone;

/* Maximum cache size for any given BSDF? */
unsigned long           SDmaxCache = 0;         /* 0 == unlimited */

/* Report any error to the indicated stream */
SDError
SDreportError(SDError ec, FILE *fp)
{
        if (!ec)
                return SDEnone;
        if ((ec < SDEnone) | (ec > SDEunknown)) {
                SDerrorDetail[0] = '\0';
                ec = SDEunknown;
        }
        if (fp == NULL)
                return ec;
        fputs(SDerrorList[ec], fp);
        if (SDerrorDetail[0]) {
                fputs(": ", fp);
                fputs(SDerrorDetail, fp);
        }
        fputc('\n', fp);
        if (fp != stderr)
                fflush(fp);
        return ec;
}

static double
to_meters(              /* return factor to convert given unit to meters */
        const char *unit
)
{
        if (unit == NULL) return(1.);           /* safe assumption? */
        if (!strcasecmp(unit, "Meter")) return(1.);
        if (!strcasecmp(unit, "Foot")) return(.3048);
        if (!strcasecmp(unit, "Inch")) return(.0254);
        if (!strcasecmp(unit, "Centimeter")) return(.01);
        if (!strcasecmp(unit, "Millimeter")) return(.001);
        sprintf(SDerrorDetail, "Unknown dimensional unit '%s'", unit);
        return(-1.);
}

/* Load geometric dimensions and description (if any) */
static SDError
SDloadGeometry(SDData *sd, ezxml_t wtl)
{
        ezxml_t         node, matl, geom;
        double          cfact;
        const char      *fmt = NULL, *mgfstr;

        SDerrorDetail[0] = '\0';
        sd->matn[0] = '\0'; sd->makr[0] = '\0';
        sd->dim[0] = sd->dim[1] = sd->dim[2] = 0;
        matl = ezxml_child(wtl, "Material");
        if (matl != NULL) {                     /* get material info. */
                if ((node = ezxml_child(matl, "Name")) != NULL) {
                        strncpy(sd->matn, ezxml_txt(node), SDnameLn);
                        if (sd->matn[SDnameLn-1])
                                strcpy(sd->matn+(SDnameLn-4), "...");
                }
                if ((node = ezxml_child(matl, "Manufacturer")) != NULL) {
                        strncpy(sd->makr, ezxml_txt(node), SDnameLn);
                        if (sd->makr[SDnameLn-1])
                                strcpy(sd->makr+(SDnameLn-4), "...");
                }
                if ((node = ezxml_child(matl, "Width")) != NULL)
                        sd->dim[0] = atof(ezxml_txt(node)) *
                                        to_meters(ezxml_attr(node, "unit"));
                if ((node = ezxml_child(matl, "Height")) != NULL)
                        sd->dim[1] = atof(ezxml_txt(node)) *
                                        to_meters(ezxml_attr(node, "unit"));
                if ((node = ezxml_child(matl, "Thickness")) != NULL)
                        sd->dim[2] = atof(ezxml_txt(node)) *
                                        to_meters(ezxml_attr(node, "unit"));
                if ((sd->dim[0] < 0) | (sd->dim[1] < 0) | (sd->dim[2] < 0)) {
                        if (!SDerrorDetail[0])
                                sprintf(SDerrorDetail, "Negative dimension in \"%s\"",
                                                        sd->name);
                        return SDEdata;
                }
        }
        sd->mgf = NULL;
        geom = ezxml_child(wtl, "Geometry");
        if (geom == NULL)                       /* no actual geometry? */
                return SDEnone;
        fmt = ezxml_attr(geom, "format");
        if (fmt != NULL && strcasecmp(fmt, "MGF")) {
                sprintf(SDerrorDetail,
                        "Unrecognized geometry format '%s' in \"%s\"",
                                        fmt, sd->name);
                return SDEsupport;
        }
        if ((node = ezxml_child(geom, "MGFblock")) == NULL ||
                        (mgfstr = ezxml_txt(node)) == NULL)
                return SDEnone;
        while (isspace(*mgfstr))
                ++mgfstr;
        if (!*mgfstr)
                return SDEnone;
        cfact = to_meters(ezxml_attr(node, "unit"));
        if (cfact <= 0)
                return SDEformat;
        sd->mgf = (char *)malloc(strlen(mgfstr)+32);
        if (sd->mgf == NULL) {
                strcpy(SDerrorDetail, "Out of memory in SDloadGeometry");
                return SDEmemory;
        }
        if (cfact < 0.99 || cfact > 1.01)
                sprintf(sd->mgf, "xf -s %.5f\n%s\nxf\n", cfact, mgfstr);
        else
                strcpy(sd->mgf, mgfstr);
        return SDEnone;
}

/* Load a BSDF struct from the given file (free first and keep name) */
SDError
SDloadFile(SDData *sd, const char *fname)
{
        SDError         lastErr;
        ezxml_t         fl, wtl;

        if ((sd == NULL) | (fname == NULL || !*fname))
                return SDEargument;
                                /* free old data, keeping name */
        SDfreeBSDF(sd);
                                /* parse XML file */
        fl = ezxml_parse_file(fname);
        if (fl == NULL) {
                sprintf(SDerrorDetail, "Cannot open BSDF \"%s\"", fname);
                return SDEfile;
        }
        if (ezxml_error(fl)[0]) {
                sprintf(SDerrorDetail, "BSDF \"%s\" %s", fname, ezxml_error(fl));
                ezxml_free(fl);
                return SDEformat;
        }
        if (strcmp(ezxml_name(fl), "WindowElement")) {
                sprintf(SDerrorDetail,
                        "BSDF \"%s\": top level node not 'WindowElement'",
                                sd->name);
                ezxml_free(fl);
                return SDEformat;
        }
        wtl = ezxml_child(fl, "FileType");
        if (wtl != NULL && strcmp(ezxml_txt(wtl), "BSDF")) {
                sprintf(SDerrorDetail,
                        "XML \"%s\": wrong FileType (must be 'BSDF')",
                                sd->name);
                ezxml_free(fl);
                return SDEformat;
        }
        wtl = ezxml_child(ezxml_child(fl, "Optical"), "Layer");
        if (wtl == NULL) {
                sprintf(SDerrorDetail, "BSDF \"%s\": no optical layers",
                                sd->name);
                ezxml_free(fl);
                return SDEformat;
        }
                                /* load geometry if present */
        lastErr = SDloadGeometry(sd, wtl);
        if (lastErr) {
                ezxml_free(fl);
                return lastErr;
        }
                                /* try loading variable resolution data */
        lastErr = SDloadTre(sd, wtl);
                                /* check our result */
        if (lastErr == SDEsupport)      /* try matrix BSDF if not tree data */
                lastErr = SDloadMtx(sd, wtl);
                
                                /* done with XML file */
        ezxml_free(fl);
        
        if (lastErr) {          /* was there a load error? */
                SDfreeBSDF(sd);
                return lastErr;
        }
                                /* remove any insignificant components */
        if (sd->rf != NULL && sd->rf->maxHemi <= .001) {
                SDfreeSpectralDF(sd->rf); sd->rf = NULL;
        }
        if (sd->rb != NULL && sd->rb->maxHemi <= .001) {
                SDfreeSpectralDF(sd->rb); sd->rb = NULL;
        }
        if (sd->tf != NULL && sd->tf->maxHemi <= .001) {
                SDfreeSpectralDF(sd->tf); sd->tf = NULL;
        }
        if (sd->tb != NULL && sd->tb->maxHemi <= .001) {
                SDfreeSpectralDF(sd->tb); sd->tb = NULL;
        }
                                /* return success */
        return SDEnone;
}

/* Allocate new spectral distribution function */
SDSpectralDF *
SDnewSpectralDF(int nc)
{
        SDSpectralDF    *df;
        
        if (nc <= 0) {
                strcpy(SDerrorDetail, "Zero component spectral DF request");
                return NULL;
        }
        df = (SDSpectralDF *)malloc(sizeof(SDSpectralDF) +
                                        (nc-1)*sizeof(SDComponent));
        if (df == NULL) {
                sprintf(SDerrorDetail,
                                "Cannot allocate %d component spectral DF", nc);
                return NULL;
        }
        df->minProjSA = .0;
        df->maxHemi = .0;
        df->ncomp = nc;
        memset(df->comp, 0, nc*sizeof(SDComponent));
        return df;
}

/* Add component(s) to spectral distribution function */
SDSpectralDF *
SDaddComponent(SDSpectralDF *odf, int nadd)
{
        SDSpectralDF    *df;

        if (odf == NULL)
                return SDnewSpectralDF(nadd);
        if (nadd <= 0)
                return odf;
        df = (SDSpectralDF *)realloc(odf, sizeof(SDSpectralDF) +
                                (odf->ncomp+nadd-1)*sizeof(SDComponent));
        if (df == NULL) {
                sprintf(SDerrorDetail,
                        "Cannot add %d component(s) to spectral DF", nadd);
                SDfreeSpectralDF(odf);
                return NULL;
        }
        memset(df->comp+df->ncomp, 0, nadd*sizeof(SDComponent));
        df->ncomp += nadd;
        return df;
}

/* Free cached cumulative distributions for BSDF component */
void
SDfreeCumulativeCache(SDSpectralDF *df)
{
        int     n;
        SDCDst  *cdp;

        if (df == NULL)
                return;
        for (n = df->ncomp; n-- > 0; )
                while ((cdp = df->comp[n].cdList) != NULL) {
                        df->comp[n].cdList = cdp->next;
                        free(cdp);
                }
}

/* Free a spectral distribution function */
void
SDfreeSpectralDF(SDSpectralDF *df)
{
        int     n;

        if (df == NULL)
                return;
        SDfreeCumulativeCache(df);
        for (n = df->ncomp; n-- > 0; )
                if (df->comp[n].dist != NULL)
                        (*df->comp[n].func->freeSC)(df->comp[n].dist);
        free(df);
}

/* Shorten file path to useable BSDF name, removing suffix */
void
SDclipName(char *res, const char *fname)
{
        const char      *cp, *dot = NULL;
        
        for (cp = fname; *cp; cp++)
                if (*cp == '.')
                        dot = cp;
                else if (*cp == '/')
                        dot = NULL;
        if ((dot == NULL) | (dot < fname+2))
                dot = cp;
        if (dot - fname >= SDnameLn)
                fname = dot - SDnameLn + 1;
        while (fname < dot)
                *res++ = *fname++;
        *res = '\0';
}

/* Initialize an unused BSDF struct (simply clears to zeroes) */
void
SDclearBSDF(SDData *sd, const char *fname)
{
        if (sd == NULL)
                return;
        memset(sd, 0, sizeof(SDData));
        if (fname == NULL)
                return;
        SDclipName(sd->name, fname);
}

/* Free data associated with BSDF struct */
void
SDfreeBSDF(SDData *sd)
{
        if (sd == NULL)
                return;
        if (sd->mgf != NULL) {
                free(sd->mgf);
                sd->mgf = NULL;
        }
        if (sd->rf != NULL) {
                SDfreeSpectralDF(sd->rf);
                sd->rf = NULL;
        }
        if (sd->rb != NULL) {
                SDfreeSpectralDF(sd->rb);
                sd->rb = NULL;
        }
        if (sd->tf != NULL) {
                SDfreeSpectralDF(sd->tf);
                sd->tf = NULL;
        }
        if (sd->tb != NULL) {
                SDfreeSpectralDF(sd->tb);
                sd->tb = NULL;
        }
        sd->rLambFront.cieY = .0;
        sd->rLambFront.spec.flags = 0;
        sd->rLambBack.cieY = .0;
        sd->rLambBack.spec.flags = 0;
        sd->tLambFront.cieY = .0;
        sd->tLambFront.spec.flags = 0;
        sd->tLambBack.cieY = .0;
        sd->tLambBack.spec.flags = 0;
}

/* Find writeable BSDF by name, or allocate new cache entry if absent */
SDData *
SDgetCache(const char *bname)
{
        struct SDCache_s        *sdl;
        char                    sdnam[SDnameLn];

        if (bname == NULL)
                return NULL;

        SDclipName(sdnam, bname);
        for (sdl = SDcacheList; sdl != NULL; sdl = sdl->next)
                if (!strcmp(sdl->bsdf.name, sdnam)) {
                        sdl->refcnt++;
                        return &sdl->bsdf;
                }

        sdl = (struct SDCache_s *)calloc(1, sizeof(struct SDCache_s));
        if (sdl == NULL)
                return NULL;

        strcpy(sdl->bsdf.name, sdnam);
        sdl->next = SDcacheList;
        SDcacheList = sdl;

        sdl->refcnt = 1;
        return &sdl->bsdf;
}

/* Get loaded BSDF from cache (or load and cache it on first call) */
/* Report any problem to stderr and return NULL on failure */
const SDData *
SDcacheFile(const char *fname)
{
        SDData          *sd;
        SDError         ec;
        
        if (fname == NULL || !*fname)
                return NULL;
        SDerrorDetail[0] = '\0';
        /* PLACE MUTEX LOCK HERE FOR THREAD-SAFE */
        if ((sd = SDgetCache(fname)) == NULL) {
                SDreportError(SDEmemory, stderr);
                return NULL;
        }
        if (!SDisLoaded(sd) && (ec = SDloadFile(sd, fname))) {
                SDreportError(ec, stderr);
                SDfreeCache(sd);
                sd = NULL;
        }
        /* END MUTEX LOCK */
        return sd;
}

/* Free a BSDF from our cache (clear all if NULL) */
void
SDfreeCache(const SDData *sd)
{
        struct SDCache_s        *sdl, *sdLast = NULL;

        if (sd == NULL) {               /* free entire list */
                while ((sdl = SDcacheList) != NULL) {
                        SDcacheList = sdl->next;
                        SDfreeBSDF(&sdl->bsdf);
                        free(sdl);
                }
                return;
        }
        for (sdl = SDcacheList; sdl != NULL; sdl = (sdLast=sdl)->next)
                if (&sdl->bsdf == sd)
                        break;
        if (sdl == NULL || (sdl->refcnt -= (sdl->refcnt > 0)))
                return;                 /* missing or still in use */
                                        /* keep unreferenced data? */
        if (SDisLoaded(sd) && SDretainSet) {
                if (SDretainSet == SDretainAll)
                        return;         /* keep everything */
                                        /* else free cumulative data */
                SDfreeCumulativeCache(sd->rf);
                SDfreeCumulativeCache(sd->rb);
                SDfreeCumulativeCache(sd->tf);
                SDfreeCumulativeCache(sd->tb);
                return;
        }
                                        /* remove from list and free */
        if (sdLast == NULL)
                SDcacheList = sdl->next;
        else
                sdLast->next = sdl->next;
        SDfreeBSDF(&sdl->bsdf);
        free(sdl);
}

/* Sample an individual BSDF component */
SDError
SDsampComponent(SDValue *sv, FVECT ioVec, double randX, SDComponent *sdc)
{
        float           coef[SDmaxCh];
        SDError         ec;
        FVECT           inVec;
        const SDCDst    *cd;
        double          d;
        int             n;
                                        /* check arguments */
        if ((sv == NULL) | (ioVec == NULL) | (sdc == NULL))
                return SDEargument;
                                        /* get cumulative distribution */
        VCOPY(inVec, ioVec);
        sv->cieY = 0;
        cd = (*sdc->func->getCDist)(inVec, sdc);
        if (cd != NULL)
                sv->cieY = cd->cTotal;
        if (sv->cieY <= 1e-6) {         /* nothing to sample? */
                sv->spec = c_dfcolor;
                memset(ioVec, 0, sizeof(FVECT));
                return SDEnone;
        }
                                        /* compute sample direction */
        ec = (*sdc->func->sampCDist)(ioVec, randX, cd);
        if (ec)
                return ec;
                                        /* get BSDF color */
        n = (*sdc->func->getBSDFs)(coef, inVec, ioVec, sdc);
        if (n <= 0) {
                strcpy(SDerrorDetail, "BSDF sample value error");
                return SDEinternal;
        }
        sv->spec = sdc->cspec[0];
        d = coef[0];
        while (--n) {
                c_cmix(&sv->spec, d, &sv->spec, coef[n], &sdc->cspec[n]);
                d += coef[n];
        }
        c_ccvt(&sv->spec, C_CSXY);      /* make sure (x,y) is set */
        return SDEnone;
}

#define MS_MAXDIM       15

/* Convert 1-dimensional random variable to N-dimensional */
void
SDmultiSamp(double t[], int n, double randX)
{
        unsigned        nBits;
        double          scale;
        bitmask_t       ndx, coord[MS_MAXDIM];

        if (n <= 0)                     /* check corner cases */
                return;
        if (randX < 0) randX = 0;
        else if (randX >= 1.) randX = 0.999999999999999;
        if (n == 1) {
                t[0] = randX;
                return;
        }
        while (n > MS_MAXDIM)           /* punt for higher dimensions */
                t[--n] = rand()*(1./(RAND_MAX+.5));
        nBits = (8*sizeof(bitmask_t) - 1) / n;
        ndx = randX * (double)((bitmask_t)1 << (nBits*n));
                                        /* get coordinate on Hilbert curve */
        hilbert_i2c(n, nBits, ndx, coord);
                                        /* convert back to [0,1) range */
        scale = 1. / (double)((bitmask_t)1 << nBits);
        while (n--)
                t[n] = scale * ((double)coord[n] + rand()*(1./(RAND_MAX+.5)));
}

#undef MS_MAXDIM

/* Generate diffuse hemispherical sample */
static void
SDdiffuseSamp(FVECT ioVec, int outFront, double randX)
{
                                        /* convert to position on hemisphere */
        SDmultiSamp(ioVec, 2, randX);
        SDsquare2disk(ioVec, ioVec[0], ioVec[1]);
        ioVec[2] = 1. - ioVec[0]*ioVec[0] - ioVec[1]*ioVec[1];
        ioVec[2] = sqrt(ioVec[2]*(ioVec[2]>0));
        if (!outFront)                  /* going out back? */
                ioVec[2] = -ioVec[2];
}

/* Query projected solid angle coverage for non-diffuse BSDF direction */
SDError
SDsizeBSDF(double *projSA, const FVECT v1, const RREAL *v2,
                                int qflags, const SDData *sd)
{
        SDSpectralDF    *rdf, *tdf;
        SDError         ec;
        int             i;
                                        /* check arguments */
        if ((projSA == NULL) | (v1 == NULL) | (sd == NULL))
                return SDEargument;
                                        /* initialize extrema */
        switch (qflags) {
        case SDqueryMax:
                projSA[0] = .0;
                break;
        case SDqueryMin+SDqueryMax:
                projSA[1] = .0;
                /* fall through */
        case SDqueryMin:
                projSA[0] = 10.;
                break;
        case 0:
                return SDEargument;
        }
        if (v1[2] > 0) {                /* front surface query? */
                rdf = sd->rf;
                tdf = (sd->tf != NULL) ? sd->tf : sd->tb;
        } else {
                rdf = sd->rb;
                tdf = (sd->tb != NULL) ? sd->tb : sd->tf;
        }
        if (v2 != NULL) {               /* bidirectional? */
                if (v1[2] > 0 ^ v2[2] > 0)
                        rdf = NULL;
                else
                        tdf = NULL;
        }
        ec = SDEdata;                   /* run through components */
        for (i = (rdf==NULL) ? 0 : rdf->ncomp; i--; ) {
                ec = (*rdf->comp[i].func->queryProjSA)(projSA, v1, v2,
                                                qflags, &rdf->comp[i]);
                if (ec)
                        return ec;
        }
        for (i = (tdf==NULL) ? 0 : tdf->ncomp; i--; ) {
                ec = (*tdf->comp[i].func->queryProjSA)(projSA, v1, v2,
                                                qflags, &tdf->comp[i]);
                if (ec)
                        return ec;
        }
        if (ec) {                       /* all diffuse? */
                projSA[0] = M_PI;
                if (qflags == SDqueryMin+SDqueryMax)
                        projSA[1] = M_PI;
        } else if (qflags == SDqueryMin+SDqueryMax && projSA[0] > projSA[1])
                projSA[0] = projSA[1];
        return SDEnone;
}

/* Return BSDF for the given incident and scattered ray vectors */
SDError
SDevalBSDF(SDValue *sv, const FVECT inVec, const FVECT outVec, const SDData *sd)
{
        int             inFront, outFront;
        SDSpectralDF    *sdf;
        float           coef[SDmaxCh];
        int             nch, i;
                                        /* check arguments */
        if ((sv == NULL) | (outVec == NULL) | (inVec == NULL) | (sd == NULL))
                return SDEargument;
                                        /* whose side are we on? */
        inFront = (inVec[2] > 0);
        outFront = (outVec[2] > 0);
                                        /* start with diffuse portion */
        if (inFront & outFront) {
                *sv = sd->rLambFront;
                sdf = sd->rf;
        } else if (!(inFront | outFront)) {
                *sv = sd->rLambBack;
                sdf = sd->rb;
        } else if (inFront) {
                *sv = sd->tLambFront;
                sdf = (sd->tf != NULL) ? sd->tf : sd->tb;
        } else /* outFront & !inFront */ {
                *sv = sd->tLambBack;
                sdf = (sd->tb != NULL) ? sd->tb : sd->tf;
        }
        sv->cieY *= 1./M_PI;
                                        /* add non-diffuse components */
        i = (sdf != NULL) ? sdf->ncomp : 0;
        while (i-- > 0) {
                nch = (*sdf->comp[i].func->getBSDFs)(coef, inVec, outVec,
                                                        &sdf->comp[i]);
                while (nch-- > 0) {
                        c_cmix(&sv->spec, sv->cieY, &sv->spec,
                                        coef[nch], &sdf->comp[i].cspec[nch]);
                        sv->cieY += coef[nch];
                }
        }
        c_ccvt(&sv->spec, C_CSXY);      /* make sure (x,y) is set */
        return SDEnone;
}

/* Compute directional hemispherical scattering at this incident angle */
double
SDdirectHemi(const FVECT inVec, int sflags, const SDData *sd)
{
        double          hsum;
        SDSpectralDF    *rdf, *tdf;
        const SDCDst    *cd;
        int             i;
                                        /* check arguments */
        if ((inVec == NULL) | (sd == NULL))
                return .0;
                                        /* gather diffuse components */
        if (inVec[2] > 0) {
                hsum = sd->rLambFront.cieY;
                rdf = sd->rf;
                tdf = (sd->tf != NULL) ? sd->tf : sd->tb;
        } else /* !inFront */ {
                hsum = sd->rLambBack.cieY;
                rdf = sd->rb;
                tdf = (sd->tb != NULL) ? sd->tb : sd->tf;
        }
        if ((sflags & SDsampDf+SDsampR) != SDsampDf+SDsampR)
                hsum = .0;
        if ((sflags & SDsampDf+SDsampT) == SDsampDf+SDsampT)
                hsum += (inVec[2] > 0) ?
                                sd->tLambFront.cieY : sd->tLambBack.cieY;
                                        /* gather non-diffuse components */
        i = (((sflags & SDsampSp+SDsampR) == SDsampSp+SDsampR) &
                        (rdf != NULL)) ? rdf->ncomp : 0;
        while (i-- > 0) {               /* non-diffuse reflection */
                cd = (*rdf->comp[i].func->getCDist)(inVec, &rdf->comp[i]);
                if (cd != NULL)
                        hsum += cd->cTotal;
        }
        i = (((sflags & SDsampSp+SDsampT) == SDsampSp+SDsampT) &
                        (tdf != NULL)) ? tdf->ncomp : 0;
        while (i-- > 0) {               /* non-diffuse transmission */
                cd = (*tdf->comp[i].func->getCDist)(inVec, &tdf->comp[i]);
                if (cd != NULL)
                        hsum += cd->cTotal;
        }
        return hsum;
}

/* Sample BSDF direction based on the given random variable */
SDError
SDsampBSDF(SDValue *sv, FVECT ioVec, double randX, int sflags, const SDData *sd)
{
        SDError         ec;
        FVECT           inVec;
        int             inFront;
        SDSpectralDF    *rdf, *tdf;
        double          rdiff;
        float           coef[SDmaxCh];
        int             i, j, n, nr;
        SDComponent     *sdc;
        const SDCDst    **cdarr = NULL;
                                        /* check arguments */
        if ((sv == NULL) | (ioVec == NULL) | (sd == NULL) |
                        (randX < 0) | (randX >= 1.))
                return SDEargument;
                                        /* whose side are we on? */
        VCOPY(inVec, ioVec);
        inFront = (inVec[2] > 0);
                                        /* remember diffuse portions */
        if (inFront) {
                *sv = sd->rLambFront;
                rdf = sd->rf;
                tdf = (sd->tf != NULL) ? sd->tf : sd->tb;
        } else /* !inFront */ {
                *sv = sd->rLambBack;
                rdf = sd->rb;
                tdf = (sd->tb != NULL) ? sd->tb : sd->tf;
        }
        if ((sflags & SDsampDf+SDsampR) != SDsampDf+SDsampR)
                sv->cieY = .0;
        rdiff = sv->cieY;
        if ((sflags & SDsampDf+SDsampT) == SDsampDf+SDsampT)
                sv->cieY += inFront ? sd->tLambFront.cieY : sd->tLambBack.cieY;
                                        /* gather non-diffuse components */
        i = nr = (((sflags & SDsampSp+SDsampR) == SDsampSp+SDsampR) &
                        (rdf != NULL)) ? rdf->ncomp : 0;
        j = (((sflags & SDsampSp+SDsampT) == SDsampSp+SDsampT) &
                        (tdf != NULL)) ? tdf->ncomp : 0;
        n = i + j;
        if (n > 0 && (cdarr = (const SDCDst **)malloc(n*sizeof(SDCDst *))) == NULL)
                return SDEmemory;
        while (j-- > 0) {               /* non-diffuse transmission */
                cdarr[i+j] = (*tdf->comp[j].func->getCDist)(inVec, &tdf->comp[j]);
                if (cdarr[i+j] == NULL)
                        cdarr[i+j] = &SDemptyCD;
                sv->cieY += cdarr[i+j]->cTotal;
        }
        while (i-- > 0) {               /* non-diffuse reflection */
                cdarr[i] = (*rdf->comp[i].func->getCDist)(inVec, &rdf->comp[i]);
                if (cdarr[i] == NULL)
                        cdarr[i] = &SDemptyCD;
                sv->cieY += cdarr[i]->cTotal;
        }
        if (sv->cieY <= 1e-6) {         /* anything to sample? */
                sv->cieY = .0;
                memset(ioVec, 0, sizeof(FVECT));
                return SDEnone;
        }
                                        /* scale random variable */
        randX *= sv->cieY;
                                        /* diffuse reflection? */
        if (randX < rdiff) {
                SDdiffuseSamp(ioVec, inFront, randX/rdiff);
                goto done;
        }
        randX -= rdiff;
                                        /* diffuse transmission? */
        if ((sflags & SDsampDf+SDsampT) == SDsampDf+SDsampT) {
                const SDValue   *sdt = inFront ? &sd->tLambFront : &sd->tLambBack;
                if (randX < sdt->cieY) {
                        sv->spec = sdt->spec;
                        SDdiffuseSamp(ioVec, !inFront, randX/sdt->cieY);
                        goto done;
                }
                randX -= sdt->cieY;
        }
                                        /* else one of cumulative dist. */
        for (i = 0; i < n && randX >= cdarr[i]->cTotal; i++)
                randX -= cdarr[i]->cTotal;
        if (i >= n)
                return SDEinternal;
                                        /* compute sample direction */
        sdc = (i < nr) ? &rdf->comp[i] : &tdf->comp[i-nr];
        ec = (*sdc->func->sampCDist)(ioVec, randX/cdarr[i]->cTotal, cdarr[i]);
        if (ec)
                return ec;
                                        /* compute color */
        j = (*sdc->func->getBSDFs)(coef, inVec, ioVec, sdc);
        if (j <= 0) {
                sprintf(SDerrorDetail, "BSDF \"%s\" sampling value error",
                                sd->name);
                return SDEinternal;
        }
        sv->spec = sdc->cspec[0];
        rdiff = coef[0];
        while (--j) {
                c_cmix(&sv->spec, rdiff, &sv->spec, coef[j], &sdc->cspec[j]);
                rdiff += coef[j];
        }
done:
        if (cdarr != NULL)
                free(cdarr);
        c_ccvt(&sv->spec, C_CSXY);      /* make sure (x,y) is set */
        return SDEnone;
}

/* Compute World->BSDF transform from surface normal and up (Y) vector */
SDError 
SDcompXform(RREAL vMtx[3][3], const FVECT sNrm, const FVECT uVec)
{
        if ((vMtx == NULL) | (sNrm == NULL) | (uVec == NULL))
                return SDEargument;
        VCOPY(vMtx[2], sNrm);
        if (normalize(vMtx[2]) == 0)
                return SDEargument;
        fcross(vMtx[0], uVec, vMtx[2]);
        if (normalize(vMtx[0]) == 0)
                return SDEargument;
        fcross(vMtx[1], vMtx[2], vMtx[0]);
        return SDEnone;
}

/* Compute inverse transform */
SDError 
SDinvXform(RREAL iMtx[3][3], RREAL vMtx[3][3])
{
        RREAL   mTmp[3][3];
        double  d;

        if ((iMtx == NULL) | (vMtx == NULL))
                return SDEargument;
                                        /* compute determinant */
        mTmp[0][0] = vMtx[2][2]*vMtx[1][1] - vMtx[2][1]*vMtx[1][2];
        mTmp[0][1] = vMtx[2][1]*vMtx[0][2] - vMtx[2][2]*vMtx[0][1];
        mTmp[0][2] = vMtx[1][2]*vMtx[0][1] - vMtx[1][1]*vMtx[0][2];
        d = vMtx[0][0]*mTmp[0][0] + vMtx[1][0]*mTmp[0][1] + vMtx[2][0]*mTmp[0][2];
        if (d == 0) {
                strcpy(SDerrorDetail, "Zero determinant in matrix inversion");
                return SDEargument;
        }
        d = 1./d;                       /* invert matrix */
        mTmp[0][0] *= d; mTmp[0][1] *= d; mTmp[0][2] *= d;
        mTmp[1][0] = d*(vMtx[2][0]*vMtx[1][2] - vMtx[2][2]*vMtx[1][0]);
        mTmp[1][1] = d*(vMtx[2][2]*vMtx[0][0] - vMtx[2][0]*vMtx[0][2]);
        mTmp[1][2] = d*(vMtx[1][0]*vMtx[0][2] - vMtx[1][2]*vMtx[0][0]);
        mTmp[2][0] = d*(vMtx[2][1]*vMtx[1][0] - vMtx[2][0]*vMtx[1][1]);
        mTmp[2][1] = d*(vMtx[2][0]*vMtx[0][1] - vMtx[2][1]*vMtx[0][0]);
        mTmp[2][2] = d*(vMtx[1][1]*vMtx[0][0] - vMtx[1][0]*vMtx[0][1]);
        memcpy(iMtx, mTmp, sizeof(mTmp));
        return SDEnone;
}

/* Transform and normalize direction (column) vector */
SDError
SDmapDir(FVECT resVec, RREAL vMtx[3][3], const FVECT inpVec)
{
        FVECT   vTmp;

        if ((resVec == NULL) | (inpVec == NULL))
                return SDEargument;
        if (vMtx == NULL) {             /* assume they just want to normalize */
                if (resVec != inpVec)
                        VCOPY(resVec, inpVec);
                return (normalize(resVec) > 0) ? SDEnone : SDEargument;
        }
        vTmp[0] = DOT(vMtx[0], inpVec);
        vTmp[1] = DOT(vMtx[1], inpVec);
        vTmp[2] = DOT(vMtx[2], inpVec);
        if (normalize(vTmp) == 0)
                return SDEargument;
        VCOPY(resVec, vTmp);
        return SDEnone;
}
Revision:	2.61
Committed:	Tue Dec 7 23:49:50 2021 UTC (2 years, 5 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.60:	+11 -11 lines
Log Message:	fix: Repaired issue with reciprocity and BSDF sampling, thanks to Jon Sargent