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source.c

#ifndef lint
static const char RCSid[] = "$Id: source.c,v 2.56 2007/07/25 04:12:36 greg Exp $";
#endif
/*
 *  source.c - routines dealing with illumination sources.
 *
 *  External symbols declared in source.h
 */

#include  "ray.h"
#include  "otypes.h"
#include  "rtotypes.h"
#include  "source.h"
#include  "random.h"

extern double  ssampdist;           /* scatter sampling distance */

#ifndef MAXSSAMP
#define MAXSSAMP  16          /* maximum samples per ray */
#endif

/*
 * Structures used by direct()
 */

typedef struct {
      int  sno;         /* source number */
      FVECT  dir;       /* source direction */
      COLOR  coef;            /* material coefficient */
      COLOR  val;       /* contribution */
}  CONTRIB;       /* direct contribution */

typedef struct {
      int  sndx;        /* source index (to CONTRIB array) */
      float  brt;       /* brightness (for comparison) */
}  CNTPTR;        /* contribution pointer */

static CONTRIB  *srccnt;            /* source contributions in direct() */
static CNTPTR  *cntord;             /* source ordering in direct() */
static int  maxcntr = 0;            /* size of contribution arrays */

static int cntcmp(const void *p1, const void *p2);


extern OBJREC *               /* find an object's actual material */
findmaterial(register OBJREC *o)
{
      while (!ismaterial(o->otype)) {
            if (o->otype == MOD_ALIAS && o->oargs.nsargs) {
                  OBJECT  aobj;
                  OBJREC  *ao;
                  aobj = lastmod(objndx(o), o->oargs.sarg[0]);
                  if (aobj < 0)
                        objerror(o, USER, "bad reference");
                  ao = objptr(aobj);
                  if (ismaterial(ao->otype))
                        return(ao);
                  if (ao->otype == MOD_ALIAS) {
                        o = ao;
                        continue;
                  }
            }
            if (o->omod == OVOID)
                  return(NULL);
            o = objptr(o->omod);
      }
      return(o);        /* mixtures will return NULL */
}


extern void
marksources(void)             /* find and mark source objects */
{
      int  foundsource = 0;
      int  i;
      register OBJREC  *o, *m;
      register int  ns;
                              /* initialize dispatch table */
      initstypes();
                              /* find direct sources */
      for (i = 0; i < nsceneobjs; i++) {
      
            o = objptr(i);

            if (!issurface(o->otype) || o->omod == OVOID)
                  continue;
                              /* find material */
            m = findmaterial(objptr(o->omod));
            if (m == NULL)
                  continue;
            if (m->otype == MAT_CLIP) {
                  markclip(m);      /* special case for antimatter */
                  continue;
            }
            if (!islight(m->otype))
                  continue;   /* not source modifier */
      
            if (m->oargs.nfargs != (m->otype == MAT_GLOW ? 4 :
                        m->otype == MAT_SPOT ? 7 : 3))
                  objerror(m, USER, "bad # arguments");

            if (m->otype == MAT_GLOW &&
                        o->otype != OBJ_SOURCE &&
                        m->oargs.farg[3] <= FTINY)
                  continue;               /* don't bother */
            if (m->oargs.farg[0] <= FTINY && m->oargs.farg[1] <= FTINY &&
                        m->oargs.farg[2] <= FTINY)
                  continue;               /* don't bother */

            if (sfun[o->otype].of == NULL ||
                        sfun[o->otype].of->setsrc == NULL)
                  objerror(o, USER, "illegal material");

            if ((ns = newsource()) < 0)
                  goto memerr;

            setsource(&source[ns], o);

            if (m->otype == MAT_GLOW) {
                  source[ns].sflags |= SPROX;
                  source[ns].sl.prox = m->oargs.farg[3];
                  if (source[ns].sflags & SDISTANT)
                        source[ns].sflags |= SSKIP;
            } else if (m->otype == MAT_SPOT) {
                  source[ns].sflags |= SSPOT;
                  if ((source[ns].sl.s = makespot(m)) == NULL)
                        goto memerr;
                  if (source[ns].sflags & SFLAT &&
                        !checkspot(source[ns].sl.s,source[ns].snorm)) {
                        objerror(o, WARNING,
                              "invalid spotlight direction");
                        source[ns].sflags |= SSKIP;
                  }
            }
#if  SHADCACHE
            initobscache(ns);
#endif
            if (!(source[ns].sflags & SSKIP))
                  foundsource++;
      }
      if (!foundsource) {
            error(WARNING, "no light sources found");
            return;
      }
      markvirtuals();               /* find and add virtual sources */
                        /* allocate our contribution arrays */
      maxcntr = nsources + MAXSPART;      /* start with this many */
      srccnt = (CONTRIB *)malloc(maxcntr*sizeof(CONTRIB));
      cntord = (CNTPTR *)malloc(maxcntr*sizeof(CNTPTR));
      if ((srccnt == NULL) | (cntord == NULL))
            goto memerr;
      return;
memerr:
      error(SYSTEM, "out of memory in marksources");
}


extern void
freesources(void)             /* free all source structures */
{
      if (nsources > 0) {
#if SHADCACHE
            while (nsources--)
                  freeobscache(&source[nsources]);
#endif
            free((void *)source);
            source = NULL;
            nsources = 0;
      }
      if (maxcntr <= 0)
            return;
      free((void *)srccnt);
      srccnt = NULL;
      free((void *)cntord);
      cntord = NULL;
      maxcntr = 0;
}


extern int
srcray(                       /* send a ray to a source, return domega */
      register RAY  *sr,            /* returned source ray */
      RAY  *r,                /* ray which hit object */
      SRCINDEX  *si                 /* source sample index */
)
{
    double  d;                      /* distance to source */
    register SRCREC  *srcp;

    rayorigin(sr, SHADOW, r, NULL);       /* ignore limits */

    while ((d = nextssamp(sr, si)) != 0.0) {
      sr->rsrc = si->sn;                  /* remember source */
      srcp = source + si->sn;
      if (srcp->sflags & SDISTANT) {
            if (srcp->sflags & SSPOT && spotout(sr, srcp->sl.s))
                  continue;
            return(1);        /* sample OK */
      }
                        /* local source */
                                    /* check proximity */
      if (srcp->sflags & SPROX && d > srcp->sl.prox)
            continue;
                                    /* check angle */
      if (srcp->sflags & SSPOT) {
            if (spotout(sr, srcp->sl.s))
                  continue;
                              /* adjust solid angle */
            si->dom *= d*d;
            d += srcp->sl.s->flen;
            si->dom /= d*d;
      }
      return(1);              /* sample OK */
    }
    return(0);                /* no more samples */
}


extern void
srcvalue(               /* punch ray to source and compute value */
      register RAY  *r
)
{
      register SRCREC  *sp;

      sp = &source[r->rsrc];
      if (sp->sflags & SVIRTUAL) {  /* virtual source */
                              /* check intersection */
            if (!(*ofun[sp->so->otype].funp)(sp->so, r))
                  return;
            if (!rayshade(r, r->ro->omod))      /* compute contribution */
                  goto nomat;
            rayparticipate(r);
            return;
      }
                              /* compute intersection */
      if (sp->sflags & SDISTANT ? sourcehit(r) :
                  (*ofun[sp->so->otype].funp)(sp->so, r)) {
            if (sp->sa.success >= 0)
                  sp->sa.success++;
            if (!rayshade(r, r->ro->omod))      /* compute contribution */
                  goto nomat;
            rayparticipate(r);
            return;
      }
                              /* we missed our mark! */
      if (sp->sa.success < 0)
            return;                 /* bitched already */
      sp->sa.success -= AIMREQT;
      if (sp->sa.success >= 0)
            return;                 /* leniency */
      sprintf(errmsg, "aiming failure for light source \"%s\"",
                  sp->so->oname);
      error(WARNING, errmsg);       /* issue warning */
      return;
nomat:
      objerror(r->ro, USER, "material not found");
}


static int
transillum(             /* check if material is transparent illum */
      OBJECT      obj
)
{
      OBJREC *m = findmaterial(objptr(obj));
      
      if (m == NULL)
            return(1);
      if (m->otype != MAT_ILLUM)
            return(0);
      return(!m->oargs.nsargs || !strcmp(m->oargs.sarg[0], VOIDID));
}


extern int
sourcehit(              /* check to see if ray hit distant source */
      register RAY  *r
)
{
      int  glowsrc = -1;
      int  transrc = -1;
      int  first, last;
      register int  i;

      if (r->rsrc >= 0) {           /* check only one if aimed */
            first = last = r->rsrc;
      } else {                /* otherwise check all */
            first = 0; last = nsources-1;
      }
      for (i = first; i <= last; i++) {
            if ((source[i].sflags & (SDISTANT|SVIRTUAL)) != SDISTANT)
                  continue;
            /*
             * Check to see if ray is within
             * solid angle of source.
             */
            if (2.*PI*(1. - DOT(source[i].sloc,r->rdir)) > source[i].ss2)
                  continue;
                              /* is it the only possibility? */
            if (first == last) {
                  r->ro = source[i].so;
                  break;
            }
            /*
             * If it's a glow or transparent illum, just remember it.
             */
            if (source[i].sflags & SSKIP) {
                  glowsrc = i;
                  continue;
            }
            if (transillum(source[i].so->omod)) {
                  transrc = i;
                  continue;
            }
            r->ro = source[i].so;   /* otherwise, use first hit */
            break;
      }
      /*
       * Do we need fallback?
       */
      if (r->ro == NULL) {
            if (transrc >= 0 && r->crtype & (AMBIENT|SPECULAR))
                  return(0);  /* avoid overcounting */
            if (glowsrc >= 0)
                  r->ro = source[glowsrc].so;
            else
                  return(0);  /* nothing usable */
      }
      /*
       * Make assignments.
       */
      r->robj = objndx(r->ro);
      for (i = 0; i < 3; i++)
            r->ron[i] = -r->rdir[i];
      r->rod = 1.0;
      r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
      r->uv[0] = r->uv[1] = 0.0;
      r->rox = NULL;
      return(1);
}


static int
cntcmp(                       /* contribution compare (descending) */
      const void *p1,
      const void *p2
)
{
      register const CNTPTR  *sc1 = (const CNTPTR *)p1;
      register const CNTPTR  *sc2 = (const CNTPTR *)p2;

      if (sc1->brt > sc2->brt)
            return(-1);
      if (sc1->brt < sc2->brt)
            return(1);
      return(0);
}


extern void
direct(                             /* add direct component */
      RAY  *r,                /* ray that hit surface */
      srcdirf_t *f,                 /* direct component coefficient function */
      void  *p                /* data for f */
)
{
      register int  sn;
      register CONTRIB  *scp;
      SRCINDEX  si;
      int  nshadcheck, ncnts;
      int  nhits;
      double  prob, ourthresh, hwt;
      RAY  sr;
                  /* NOTE: srccnt and cntord global so no recursion */
      if (nsources <= 0)
            return;           /* no sources?! */
                                    /* potential contributions */
      initsrcindex(&si);
      for (sn = 0; srcray(&sr, r, &si); sn++) {
            if (sn >= maxcntr) {
                  maxcntr = sn + MAXSPART;
                  srccnt = (CONTRIB *)realloc((void *)srccnt,
                              maxcntr*sizeof(CONTRIB));
                  cntord = (CNTPTR *)realloc((void *)cntord,
                              maxcntr*sizeof(CNTPTR));
                  if ((srccnt == NULL) | (cntord == NULL))
                        error(SYSTEM, "out of memory in direct");
            }
            cntord[sn].sndx = sn;
            scp = srccnt + sn;
            scp->sno = sr.rsrc;
                                    /* compute coefficient */
            (*f)(scp->coef, p, sr.rdir, si.dom);
            cntord[sn].brt = intens(scp->coef);
            if (cntord[sn].brt <= 0.0)
                  continue;
#if SHADCACHE
                                    /* check shadow cache */
            if (si.np == 1 && srcblocked(&sr)) {
                  cntord[sn].brt = 0.0;
                  continue;
            }
#endif
            VCOPY(scp->dir, sr.rdir);
            copycolor(sr.rcoef, scp->coef);
                                    /* compute potential */
            sr.revf = srcvalue;
            rayvalue(&sr);
            multcolor(sr.rcol, sr.rcoef);
            copycolor(scp->val, sr.rcol);
            cntord[sn].brt = intens(sr.rcol);
      }
                                    /* sort contributions */
      qsort(cntord, sn, sizeof(CNTPTR), cntcmp);
      {                             /* find last */
            register int  l, m;

            ncnts = l = sn;
            sn = 0;
            while ((m = (sn + ncnts) >> 1) != l) {
                  if (cntord[m].brt > 0.0)
                        sn = m;
                  else
                        ncnts = m;
                  l = m;
            }
      }
      if (ncnts == 0)
            return;           /* no contributions! */
                                                /* accumulate tail */
        for (sn = ncnts-1; sn > 0; sn--)
                cntord[sn-1].brt += cntord[sn].brt;
                                    /* compute number to check */
      nshadcheck = pow((double)ncnts, shadcert) + .5;
                                    /* modify threshold */
      ourthresh = shadthresh / r->rweight;
                                    /* test for shadows */
      for (nhits = 0, hwt = 0.0, sn = 0; sn < ncnts;
                  hwt += (double)source[scp->sno].nhits /
                        (double)source[scp->sno].ntests,
                  sn++) {
                                    /* check threshold */
            if ((sn+nshadcheck>=ncnts ? cntord[sn].brt :
                        cntord[sn].brt-cntord[sn+nshadcheck].brt)
                        < ourthresh*bright(r->rcol))
                  break;
            scp = srccnt + cntord[sn].sndx;
                                    /* test for hit */
            rayorigin(&sr, SHADOW, r, NULL);
            copycolor(sr.rcoef, scp->coef);
            VCOPY(sr.rdir, scp->dir);
            sr.rsrc = scp->sno;
                                    /* keep statistics */
            if (source[scp->sno].ntests++ > 0xfffffff0) {
                  source[scp->sno].ntests >>= 1;
                  source[scp->sno].nhits >>= 1;
            }
            if (localhit(&sr, &thescene) &&
                        ( sr.ro != source[scp->sno].so ||
                        source[scp->sno].sflags & SFOLLOW )) {
                                    /* follow entire path */
                  raycont(&sr);
                  if (trace != NULL)
                        (*trace)(&sr);    /* trace execution */
                  if (bright(sr.rcol) <= FTINY) {
#if SHADCACHE
                        if ((scp <= srccnt || scp[-1].sno != scp->sno)
                                    && (scp >= srccnt+ncnts-1 ||
                                        scp[1].sno != scp->sno))
                              srcblocker(&sr);
#endif
                        continue;   /* missed! */
                  }
                  rayparticipate(&sr);
                  multcolor(sr.rcol, sr.rcoef);
                  copycolor(scp->val, sr.rcol);
            } else if (trace != NULL &&
                  (source[scp->sno].sflags & (SDISTANT|SVIRTUAL|SFOLLOW))
                                    == (SDISTANT|SFOLLOW) &&
                        sourcehit(&sr) && rayshade(&sr, sr.ro->omod)) {
                  (*trace)(&sr);          /* trace execution */
                  /* skip call to rayparticipate() & scp->val update */
            }
                                    /* add contribution if hit */
            addcolor(r->rcol, scp->val);
            nhits++;
            source[scp->sno].nhits++;
      }
                              /* source hit rate */
      if (hwt > FTINY)
            hwt = (double)nhits / hwt;
      else
            hwt = 0.5;
#ifdef DEBUG
      sprintf(errmsg, "%d tested, %d untested, %f conditional hit rate\n",
                  sn, ncnts-sn, hwt);
      eputs(errmsg);
#endif
                              /* add in untested sources */
      for ( ; sn < ncnts; sn++) {
            scp = srccnt + cntord[sn].sndx;
            prob = hwt * (double)source[scp->sno].nhits /
                        (double)source[scp->sno].ntests;
            if (prob < 1.0)
                  scalecolor(scp->val, prob);
            addcolor(r->rcol, scp->val);
      }
}


extern void
srcscatter(             /* compute source scattering into ray */
      register RAY  *r
)
{
      int  oldsampndx;
      int  nsamps;
      RAY  sr;
      SRCINDEX  si;
      double  t, d;
      double  re, ge, be;
      COLOR  cvext;
      int  i, j;

      if (r->slights == NULL || r->slights[0] == 0
                  || r->gecc >= 1.-FTINY || r->rot >= FHUGE)
            return;
      if (ssampdist <= FTINY || (nsamps = r->rot/ssampdist + .5) < 1)
            nsamps = 1;
#if MAXSSAMP
      else if (nsamps > MAXSSAMP)
            nsamps = MAXSSAMP;
#endif
      oldsampndx = samplendx;
      samplendx = random()&0x7fff;        /* randomize */
      for (i = r->slights[0]; i > 0; i--) {     /* for each source */
            for (j = 0; j < nsamps; j++) {      /* for each sample position */
                  samplendx++;
                  t = r->rot * (j+frandom())/nsamps;
                                          /* extinction */
                  re = t*colval(r->cext,RED);
                  ge = t*colval(r->cext,GRN);
                  be = t*colval(r->cext,BLU);
                  setcolor(cvext,   re > 92. ? 0. : exp(-re),
                              ge > 92. ? 0. : exp(-ge),
                              be > 92. ? 0. : exp(-be));
                  if (intens(cvext) <= FTINY)
                        break;                  /* too far away */
                  sr.rorg[0] = r->rorg[0] + r->rdir[0]*t;
                  sr.rorg[1] = r->rorg[1] + r->rdir[1]*t;
                  sr.rorg[2] = r->rorg[2] + r->rdir[2]*t;
                  sr.rmax = 0.;
                  initsrcindex(&si);      /* sample ray to this source */
                  si.sn = r->slights[i];
                  nopart(&si, &sr);
                  if (!srcray(&sr, NULL, &si) ||
                              sr.rsrc != r->slights[i])
                        continue;         /* no path */
#if SHADCACHE
                  if (srcblocked(&sr))          /* check shadow cache */
                        continue;
#endif
                  copycolor(sr.cext, r->cext);
                  copycolor(sr.albedo, r->albedo);
                  sr.gecc = r->gecc;
                  sr.slights = r->slights;
                  rayvalue(&sr);                /* eval. source ray */
                  if (bright(sr.rcol) <= FTINY) {
#if SHADCACHE
                        srcblocker(&sr);  /* add blocker to cache */
#endif
                        continue;
                  }
                  if (r->gecc <= FTINY)         /* compute P(theta) */
                        d = 1.;
                  else {
                        d = DOT(r->rdir, sr.rdir);
                        d = 1. + r->gecc*r->gecc - 2.*r->gecc*d;
                        d = (1. - r->gecc*r->gecc) / (d*sqrt(d));
                  }
                                          /* other factors */
                  d *= si.dom * r->rot / (4.*PI*nsamps);
                  multcolor(sr.rcol, r->cext);
                  multcolor(sr.rcol, r->albedo);
                  scalecolor(sr.rcol, d);
                  multcolor(sr.rcol, cvext);
                  addcolor(r->rcol, sr.rcol);   /* add it in */
            }
      }
      samplendx = oldsampndx;
}


/****************************************************************
 * The following macros were separated from the m_light() routine
 * because they are very nasty and difficult to understand.
 */

/* illumblock *
 *
 * We cannot allow an illum to pass to another illum, because that
 * would almost certainly constitute overcounting.
 * However, we do allow an illum to pass to another illum
 * that is actually going to relay to a virtual light source.
 * We also prevent an illum from passing to a glow; this provides a
 * convenient mechanism for defining detailed light source
 * geometry behind (or inside) an effective radiator.
 */

static int
weaksrcmat(OBJECT obj)        /* identify material */
{
      OBJREC *m = findmaterial(objptr(obj));
      
      if (m == NULL) return(0);
      return((m->otype==MAT_ILLUM) | (m->otype==MAT_GLOW));
}

#define  illumblock(m, r)     (!(source[r->rsrc].sflags&SVIRTUAL) && \
                        r->rod > 0.0 && \
                        weaksrcmat(source[r->rsrc].so->omod))

/* wrongsource *
 *
 * This source is the wrong source (ie. overcounted) if we are
 * aimed to a different source than the one we hit and the one
 * we hit is not an illum that should be passed.
 */

#define  wrongsource(m, r)    (r->rsrc>=0 && source[r->rsrc].so!=r->ro && \
                        (m->otype!=MAT_ILLUM || illumblock(m,r)))

/* distglow *
 *
 * A distant glow is an object that sometimes acts as a light source,
 * but is too far away from the test point to be one in this case.
 * (Glows with negative radii should NEVER participate in illumination.)
 */

#define  distglow(m, r, d)    (m->otype==MAT_GLOW && \
                        m->oargs.farg[3] >= -FTINY && \
                        d > m->oargs.farg[3])

/* badcomponent *
 *
 * We must avoid counting light sources in the ambient calculation,
 * since the direct component is handled separately.  Therefore, any
 * ambient ray which hits an active light source must be discarded.
 * The same is true for stray specular samples, since the specular
 * contribution from light sources is calculated separately.
 */

#define  badcomponent(m, r)   (r->crtype&(AMBIENT|SPECULAR) && \
                        !(r->crtype&SHADOW || r->rod < 0.0 || \
            /* not 100% correct */  distglow(m, r, r->rot)))

/* passillum *
 *
 * An illum passes to another material type when we didn't hit it
 * on purpose (as part of a direct calculation), or it is relaying
 * a virtual light source.
 */

#define  passillum(m, r)      (m->otype==MAT_ILLUM && \
                        (r->rsrc<0 || source[r->rsrc].so!=r->ro || \
                        source[r->rsrc].sflags&SVIRTUAL))

/* srcignore *
 *
 * The -dv flag is normally on for sources to be visible.
 */

#define  srcignore(m, r)      !(directvis || r->crtype&SHADOW || \
                        distglow(m, r, raydist(r,PRIMARY)))


extern int
m_light(                      /* ray hit a light source */
      register OBJREC  *m,
      register RAY  *r
)
{
                                    /* check for over-counting */
      if (badcomponent(m, r)) {
            setcolor(r->rcoef, 0.0, 0.0, 0.0);
            return(1);
      }
      if (wrongsource(m, r)) {
            setcolor(r->rcoef, 0.0, 0.0, 0.0);
            return(1);
      }
                                    /* check for passed illum */
      if (passillum(m, r)) {
            if (m->oargs.nsargs && strcmp(m->oargs.sarg[0], VOIDID))
                  return(rayshade(r,lastmod(objndx(m),m->oargs.sarg[0])));
            raytrans(r);
            return(1);
      }
                                    /* check for invisibility */
      if (srcignore(m, r)) {
            setcolor(r->rcoef, 0.0, 0.0, 0.0);
            return(1);
      }
                              /* otherwise treat as source */
                                    /* check for behind */
      if (r->rod < 0.0)
            return(1);
                                    /* check for outside spot */
      if (m->otype==MAT_SPOT && spotout(r, makespot(m)))
            return(1);
                                    /* get distribution pattern */
      raytexture(r, m->omod);
                                    /* get source color */
      setcolor(r->rcol, m->oargs.farg[0],
                    m->oargs.farg[1],
                    m->oargs.farg[2]);
                                    /* modify value */
      multcolor(r->rcol, r->pcol);
      return(1);
}

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