src/rt/raytrace.c

#ifndef lint
static const char RCSid[] = "$Id: raytrace.c,v 1.2 2014/12/01 17:32:36 taschreg Exp taschreg $";
#endif
/*
 *  raytrace.c - routines for tracing and shading rays.
 *
 *  External symbols declared in ray.h
 */

#include "copyright.h"

#include  "ray.h"
#include  "source.h"
#include  "otypes.h"
#include  "otspecial.h"
#include  "random.h"
#include  "pmap.h"

#define  MAXCSET        ((MAXSET+1)*2-1)        /* maximum check set size */

RNUMBER  raynum = 0;            /* next unique ray number */
RNUMBER  nrays = 0;             /* number of calls to localhit */

static RREAL  Lambfa[5] = {PI, PI, PI, 0.0, 0.0};
OBJREC  Lamb = {
        OVOID, MAT_PLASTIC, "Lambertian",
        {NULL, Lambfa, 0, 5}, NULL
};                                      /* a Lambertian surface */

OBJREC  Aftplane;                       /* aft clipping plane object */

#define  RAYHIT         (-1)            /* return value for intercepted ray */

static int raymove(FVECT  pos, OBJECT  *cxs, int  dirf, RAY  *r, CUBE  *cu);
static int checkhit(RAY  *r, CUBE  *cu, OBJECT  *cxs);
static void checkset(OBJECT  *os, OBJECT  *cs);


int
rayorigin(              /* start new ray from old one */
        RAY  *r,
        int  rt,
        const RAY  *ro,
        const COLOR rc
)
{
        double  rw, re;
                                                /* assign coefficient/weight */
        if (rc == NULL) {
                rw = 1.0;
                setcolor(r->rcoef, 1., 1., 1.);
        } else {
                rw = intens(rc);
                if (rc != r->rcoef)
                        copycolor(r->rcoef, rc);
        }
        if ((r->parent = ro) == NULL) {         /* primary ray */
                r->rlvl = 0;
                r->rweight = rw;
                r->crtype = r->rtype = rt;
                r->rsrc = -1;
                r->clipset = NULL;
                r->revf = raytrace;
                copycolor(r->cext, cextinction);
                copycolor(r->albedo, salbedo);
                r->gecc = seccg;
                r->slights = NULL;
        } else {                                /* spawned ray */
                if (ro->rot >= FHUGE) {
                        memset(r, 0, sizeof(RAY));
                        return(-1);             /* illegal continuation */
                }
                r->rlvl = ro->rlvl;
                if (rt & RAYREFL) {
                        r->rlvl++;
                        r->rsrc = -1;
                        r->clipset = ro->clipset;
                        r->rmax = 0.0;
                } else {
                        r->rsrc = ro->rsrc;
                        r->clipset = ro->newcset;
                        r->rmax = ro->rmax <= FTINY ? 0.0 : ro->rmax - ro->rot;
                }
                r->revf = ro->revf;
                copycolor(r->cext, ro->cext);
                copycolor(r->albedo, ro->albedo);
                r->gecc = ro->gecc;
                r->slights = ro->slights;
                r->crtype = ro->crtype | (r->rtype = rt);
                VCOPY(r->rorg, ro->rop);
                r->rweight = ro->rweight * rw;
                                                /* estimate extinction */
                re = colval(ro->cext,RED) < colval(ro->cext,GRN) ?
                                colval(ro->cext,RED) : colval(ro->cext,GRN);
                if (colval(ro->cext,BLU) < re) re = colval(ro->cext,BLU);
                re *= ro->rot;
                if (re > 0.1) {
                        if (re > 92.) {
                                r->rweight = 0.0;
                        } else {
                                r->rweight *= exp(-re);
                        }
                }
        }
        rayclear(r);
        if (r->rweight <= 0.0)                  /* check for expiration */
                return(-1);
        if (r->crtype & SHADOW)                 /* shadow commitment */
                return(0);
        if (maxdepth <= 0 && rc != NULL) {      /* Russian roulette */
                if (minweight <= 0.0)
                        error(USER, "zero ray weight in Russian roulette");
                if (maxdepth < 0 && r->rlvl > -maxdepth)
                        return(-1);             /* upper reflection limit */
                if (r->rweight >= minweight)
                        return(0);
                if (frandom() > r->rweight/minweight)
                        return(-1);
                rw = minweight/r->rweight;      /* promote survivor */
                scalecolor(r->rcoef, rw);
                r->rweight = minweight;
                return(0);
        }
        return(r->rweight >= minweight && r->rlvl <= abs(maxdepth) ? 0 : -1);
}


void
rayclear(                       /* clear a ray for (re)evaluation */
        RAY  *r
)
{
        r->rno = raynum++;
        r->newcset = r->clipset;
        r->hitf = rayhit;
        r->robj = OVOID;
        r->ro = NULL;
        r->rox = NULL;
        r->rt = r->rot = FHUGE;
        r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
        r->uv[0] = r->uv[1] = 0.0;
        setcolor(r->pcol, 1.0, 1.0, 1.0);
        setcolor(r->rcol, 0.0, 0.0, 0.0);
}


void
raytrace(                       /* trace a ray and compute its value */
        RAY  *r
)
{
        if (localhit(r, &thescene))
                raycont(r);             /* hit local surface, evaluate */
        else if (r->ro == &Aftplane) {
                r->ro = NULL;           /* hit aft clipping plane */
                r->rot = FHUGE;
        } else if (sourcehit(r))
                rayshade(r, r->ro->omod);       /* distant source */

        if (trace != NULL)
                (*trace)(r);            /* trace execution */

        rayparticipate(r);              /* for participating medium */
}


void
raycont(                        /* check for clipped object and continue */
        RAY  *r
)
{
        if ((r->clipset != NULL && inset(r->clipset, r->ro->omod)) ||
                        !rayshade(r, r->ro->omod))
                raytrans(r);
}


void
raytrans(                       /* transmit ray as is */
        RAY  *r
)
{
        RAY  tr;

        if (rayorigin(&tr, TRANS, r, NULL) == 0) {
                VCOPY(tr.rdir, r->rdir);
                rayvalue(&tr);
                copycolor(r->rcol, tr.rcol);
                r->rt = r->rot + tr.rt;
        }
}


int
rayshade(               /* shade ray r with material mod */
        RAY  *r,
        int  mod
)
{
        OBJREC  *m;

        r->rt = r->rot;                 /* set effective ray length */
        for ( ; mod != OVOID; mod = m->omod) {
                m = objptr(mod);
                /****** unnecessary test since modifier() is always called
                if (!ismodifier(m->otype)) {
                        sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
                        error(USER, errmsg);
                }
                ******/
                                        /* hack for irradiance calculation */
                if (do_irrad && !(r->crtype & ~(PRIMARY|TRANS)) &&
                                m->otype != MAT_CLIP &&
                                (ofun[m->otype].flags & (T_M|T_X))) {
                        if (irr_ignore(m->otype)) {
                                raytrans(r);
                                return(1);
                        }
                        if (!islight(m->otype))
                                m = &Lamb;
                }
                if ((*ofun[m->otype].funp)(m, r))
                        return(1);      /* materials call raytexture() */
        }
        return(0);                      /* no material! */
}


void
rayparticipate(                 /* compute ray medium participation */
        RAY  *r
)
{
        COLOR   ce, ca;
        double  re, ge, be;

        if (intens(r->cext) <= 1./FHUGE)
                return;                         /* no medium */
        re = r->rot*colval(r->cext,RED);
        ge = r->rot*colval(r->cext,GRN);
        be = r->rot*colval(r->cext,BLU);
        if (r->crtype & SHADOW) {               /* no scattering for sources */
                re *= 1. - colval(r->albedo,RED);
                ge *= 1. - colval(r->albedo,GRN);
                be *= 1. - colval(r->albedo,BLU);
        }
        setcolor(ce,    re<=FTINY ? 1. : re>92. ? 0. : exp(-re),
                        ge<=FTINY ? 1. : ge>92. ? 0. : exp(-ge),
                        be<=FTINY ? 1. : be>92. ? 0. : exp(-be));
        multcolor(r->rcol, ce);                 /* path extinction */
        if (r->crtype & SHADOW || intens(r->albedo) <= FTINY)
                return;                         /* no scattering */
        
        /* PMAP: indirect inscattering accounted for by volume photons? */
        if (!volumePhotonMapping) {
                setcolor(ca,
                        colval(r->albedo,RED)*colval(ambval,RED)*(1.-colval(ce,RED)),
                        colval(r->albedo,GRN)*colval(ambval,GRN)*(1.-colval(ce,GRN)),
                        colval(r->albedo,BLU)*colval(ambval,BLU)*(1.-colval(ce,BLU)));
                addcolor(r->rcol, ca);                  /* ambient in scattering */
        }
        
        srcscatter(r);                          /* source in scattering */
}


void
raytexture(                     /* get material modifiers */
        RAY  *r,
        OBJECT  mod
)
{
        OBJREC  *m;
                                        /* execute textures and patterns */
        for ( ; mod != OVOID; mod = m->omod) {
                m = objptr(mod);
                /****** unnecessary test since modifier() is always called
                if (!ismodifier(m->otype)) {
                        sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
                        error(USER, errmsg);
                }
                ******/
                if ((*ofun[m->otype].funp)(m, r)) {
                        sprintf(errmsg, "conflicting material \"%s\"",
                                        m->oname);
                        objerror(r->ro, USER, errmsg);
                }
        }
}


int
raymixture(             /* mix modifiers */
        RAY  *r,
        OBJECT  fore,
        OBJECT  back,
        double  coef
)
{
        RAY  fr, br;
        int  foremat, backmat;
        int  i;
                                        /* bound coefficient */
        if (coef > 1.0)
                coef = 1.0;
        else if (coef < 0.0)
                coef = 0.0;
                                        /* compute foreground and background */
        foremat = backmat = 0;
                                        /* foreground */
        fr = *r;
        if (coef > FTINY) {
                fr.rweight *= coef;
                scalecolor(fr.rcoef, coef);
                foremat = rayshade(&fr, fore);
        }
                                        /* background */
        br = *r;
        if (coef < 1.0-FTINY) {
                br.rweight *= 1.0-coef;
                scalecolor(br.rcoef, 1.0-coef);
                backmat = rayshade(&br, back);
        }
                                        /* check for transparency */
        if (backmat ^ foremat) {
                if (backmat && coef > FTINY)
                        raytrans(&fr);
                else if (foremat && coef < 1.0-FTINY)
                        raytrans(&br);
        }
                                        /* mix perturbations */
        for (i = 0; i < 3; i++)
                r->pert[i] = coef*fr.pert[i] + (1.0-coef)*br.pert[i];
                                        /* mix pattern colors */
        scalecolor(fr.pcol, coef);
        scalecolor(br.pcol, 1.0-coef);
        copycolor(r->pcol, fr.pcol);
        addcolor(r->pcol, br.pcol);
                                        /* return value tells if material */
        if (!foremat & !backmat)
                return(0);
                                        /* mix returned ray values */
        scalecolor(fr.rcol, coef);
        scalecolor(br.rcol, 1.0-coef);
        copycolor(r->rcol, fr.rcol);
        addcolor(r->rcol, br.rcol);
        r->rt = bright(fr.rcol) > bright(br.rcol) ? fr.rt : br.rt;
        return(1);
}


double
raydist(                /* compute (cumulative) ray distance */
        const RAY  *r,
        int  flags
)
{
        double  sum = 0.0;

        while (r != NULL && r->crtype&flags) {
                sum += r->rot;
                r = r->parent;
        }
        return(sum);
}


void
raycontrib(             /* compute (cumulative) ray contribution */
        RREAL  rc[3],
        const RAY  *r,
        int  flags
)
{
        double  eext[3];
        int     i;

        eext[0] = eext[1] = eext[2] = 0.;
        rc[0] = rc[1] = rc[2] = 1.;

        while (r != NULL && r->crtype&flags) {
                for (i = 3; i--; ) {
                        rc[i] *= colval(r->rcoef,i);
                        eext[i] += r->rot * colval(r->cext,i);
                }
                r = r->parent;
        }
        for (i = 3; i--; )
                rc[i] *= (eext[i] <= FTINY) ? 1. :
                                (eext[i] > 92.) ? 0. : exp(-eext[i]);
}


double
raynormal(              /* compute perturbed normal for ray */
        FVECT  norm,
        RAY  *r
)
{
        double  newdot;
        int  i;

        /*      The perturbation is added to the surface normal to obtain
         *  the new normal.  If the new normal would affect the surface
         *  orientation wrt. the ray, a correction is made.  The method is
         *  still fraught with problems since reflected rays and similar
         *  directions calculated from the surface normal may spawn rays behind
         *  the surface.  The only solution is to curb textures at high
         *  incidence (namely, keep DOT(rdir,pert) < Rdot).
         */

        for (i = 0; i < 3; i++)
                norm[i] = r->ron[i] + r->pert[i];

        if (normalize(norm) == 0.0) {
                objerror(r->ro, WARNING, "illegal normal perturbation");
                VCOPY(norm, r->ron);
                return(r->rod);
        }
        newdot = -DOT(norm, r->rdir);
        if ((newdot > 0.0) != (r->rod > 0.0)) {         /* fix orientation */
                for (i = 0; i < 3; i++)
                        norm[i] += 2.0*newdot*r->rdir[i];
                newdot = -newdot;
        }
        return(newdot);
}


void
newrayxf(                       /* get new tranformation matrix for ray */
        RAY  *r
)
{
        static struct xfn {
                struct xfn  *next;
                FULLXF  xf;
        }  xfseed = { &xfseed }, *xflast = &xfseed;
        struct xfn  *xp;
        const RAY  *rp;

        /*
         * Search for transform in circular list that
         * has no associated ray in the tree.
         */
        xp = xflast;
        for (rp = r->parent; rp != NULL; rp = rp->parent)
                if (rp->rox == &xp->xf) {               /* xp in use */
                        xp = xp->next;                  /* move to next */
                        if (xp == xflast) {             /* need new one */
                                xp = (struct xfn *)bmalloc(sizeof(struct xfn));
                                if (xp == NULL)
                                        error(SYSTEM,
                                                "out of memory in newrayxf");
                                                        /* insert in list */
                                xp->next = xflast->next;
                                xflast->next = xp;
                                break;                  /* we're done */
                        }
                        rp = r;                 /* start check over */
                }
                                        /* got it */
        r->rox = &xp->xf;
        xflast = xp;
}


void
flipsurface(                    /* reverse surface orientation */
        RAY  *r
)
{
        r->rod = -r->rod;
        r->ron[0] = -r->ron[0];
        r->ron[1] = -r->ron[1];
        r->ron[2] = -r->ron[2];
        r->pert[0] = -r->pert[0];
        r->pert[1] = -r->pert[1];
        r->pert[2] = -r->pert[2];
}


void
rayhit(                 /* standard ray hit test */
        OBJECT  *oset,
        RAY  *r
)
{
        OBJREC  *o;
        int     i;

        for (i = oset[0]; i > 0; i--) {
                o = objptr(oset[i]);
                if ((*ofun[o->otype].funp)(o, r))
                        r->robj = oset[i];
        }
}


int
localhit(               /* check for hit in the octree */
        RAY  *r,
        CUBE  *scene
)
{
        OBJECT  cxset[MAXCSET+1];       /* set of checked objects */
        FVECT  curpos;                  /* current cube position */
        int  sflags;                    /* sign flags */
        double  t, dt;
        int  i;

        nrays++;                        /* increment trace counter */
        sflags = 0;
        for (i = 0; i < 3; i++) {
                curpos[i] = r->rorg[i];
                if (r->rdir[i] > 1e-7)
                        sflags |= 1 << i;
                else if (r->rdir[i] < -1e-7)
                        sflags |= 0x10 << i;
        }
        if (!sflags) {
                error(WARNING, "zero ray direction in localhit");
                return(0);
        }
                                        /* start off assuming nothing hit */
        if (r->rmax > FTINY) {          /* except aft plane if one */
                r->ro = &Aftplane;
                r->rot = r->rmax;
                VSUM(r->rop, r->rorg, r->rdir, r->rot);
        }
                                        /* find global cube entrance point */
        t = 0.0;
        if (!incube(scene, curpos)) {
                                        /* find distance to entry */
                for (i = 0; i < 3; i++) {
                                        /* plane in our direction */
                        if (sflags & 1<<i)
                                dt = scene->cuorg[i];
                        else if (sflags & 0x10<<i)
                                dt = scene->cuorg[i] + scene->cusize;
                        else
                                continue;
                                        /* distance to the plane */
                        dt = (dt - r->rorg[i])/r->rdir[i];
                        if (dt > t)
                                t = dt; /* farthest face is the one */
                }
                t += FTINY;             /* fudge to get inside cube */
                if (t >= r->rot)        /* clipped already */
                        return(0);
                                        /* advance position */
                VSUM(curpos, curpos, r->rdir, t);

                if (!incube(scene, curpos))     /* non-intersecting ray */
                        return(0);
        }
        cxset[0] = 0;
        raymove(curpos, cxset, sflags, r, scene);
        return((r->ro != NULL) & (r->ro != &Aftplane));
}


static int
raymove(                /* check for hit as we move */
        FVECT  pos,                     /* current position, modified herein */
        OBJECT  *cxs,                   /* checked objects, modified by checkhit */
        int  dirf,                      /* direction indicators to speed tests */
        RAY  *r,
        CUBE  *cu
)
{
        int  ax;
        double  dt, t;

        if (istree(cu->cutree)) {               /* recurse on subcubes */
                CUBE  cukid;
                int  br, sgn;

                cukid.cusize = cu->cusize * 0.5;        /* find subcube */
                VCOPY(cukid.cuorg, cu->cuorg);
                br = 0;
                if (pos[0] >= cukid.cuorg[0]+cukid.cusize) {
                        cukid.cuorg[0] += cukid.cusize;
                        br |= 1;
                }
                if (pos[1] >= cukid.cuorg[1]+cukid.cusize) {
                        cukid.cuorg[1] += cukid.cusize;
                        br |= 2;
                }
                if (pos[2] >= cukid.cuorg[2]+cukid.cusize) {
                        cukid.cuorg[2] += cukid.cusize;
                        br |= 4;
                }
                for ( ; ; ) {
                        cukid.cutree = octkid(cu->cutree, br);
                        if ((ax = raymove(pos,cxs,dirf,r,&cukid)) == RAYHIT)
                                return(RAYHIT);
                        sgn = 1 << ax;
                        if (sgn & dirf)                 /* positive axis? */
                                if (sgn & br)
                                        return(ax);     /* overflow */
                                else {
                                        cukid.cuorg[ax] += cukid.cusize;
                                        br |= sgn;
                                }
                        else
                                if (sgn & br) {
                                        cukid.cuorg[ax] -= cukid.cusize;
                                        br &= ~sgn;
                                } else
                                        return(ax);     /* underflow */
                }
                /*NOTREACHED*/
        }
        if (isfull(cu->cutree)) {
                if (checkhit(r, cu, cxs))
                        return(RAYHIT);
        } else if (r->ro == &Aftplane && incube(cu, r->rop))
                return(RAYHIT);
                                        /* advance to next cube */
        if (dirf&0x11) {
                dt = dirf&1 ? cu->cuorg[0] + cu->cusize : cu->cuorg[0];
                t = (dt - pos[0])/r->rdir[0];
                ax = 0;
        } else
                t = FHUGE;
        if (dirf&0x22) {
                dt = dirf&2 ? cu->cuorg[1] + cu->cusize : cu->cuorg[1];
                dt = (dt - pos[1])/r->rdir[1];
                if (dt < t) {
                        t = dt;
                        ax = 1;
                }
        }
        if (dirf&0x44) {
                dt = dirf&4 ? cu->cuorg[2] + cu->cusize : cu->cuorg[2];
                dt = (dt - pos[2])/r->rdir[2];
                if (dt < t) {
                        t = dt;
                        ax = 2;
                }
        }
        VSUM(pos, pos, r->rdir, t);
        return(ax);
}


static int
checkhit(               /* check for hit in full cube */
        RAY  *r,
        CUBE  *cu,
        OBJECT  *cxs
)
{
        OBJECT  oset[MAXSET+1];

        objset(oset, cu->cutree);
        checkset(oset, cxs);                    /* avoid double-checking */

        (*r->hitf)(oset, r);                    /* test for hit in set */

        if (r->robj == OVOID)
                return(0);                      /* no scores yet */

        return(incube(cu, r->rop));             /* hit OK if in current cube */
}


static void
checkset(               /* modify checked set and set to check */
        OBJECT  *os,                    /* os' = os - cs */
        OBJECT  *cs                     /* cs' = cs + os */
)
{
        OBJECT  cset[MAXCSET+MAXSET+1];
        int  i, j;
        int  k;
                                        /* copy os in place, cset <- cs */
        cset[0] = 0;
        k = 0;
        for (i = j = 1; i <= os[0]; i++) {
                while (j <= cs[0] && cs[j] < os[i])
                        cset[++cset[0]] = cs[j++];
                if (j > cs[0] || os[i] != cs[j]) {      /* object to check */
                        os[++k] = os[i];
                        cset[++cset[0]] = os[i];
                }
        }
        if (!(os[0] = k))               /* new "to check" set size */
                return;                 /* special case */
        while (j <= cs[0])              /* get the rest of cs */
                cset[++cset[0]] = cs[j++];
        if (cset[0] > MAXCSET)          /* truncate "checked" set if nec. */
                cset[0] = MAXCSET;
        /* setcopy(cs, cset); */        /* copy cset back to cs */
        os = cset;
        for (i = os[0]; i-- >= 0; )
                *cs++ = *os++;
}
Revision:	2.66
Committed:	Tue Feb 24 19:39:27 2015 UTC (9 years, 2 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.65:	+12 -6 lines
Log Message:	Initial check-in of photon map addition by Roland Schregle
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.66	static const char RCSid[] = "$Id: raytrace.c,v 1.2 2014/12/01 17:32:36 taschreg Exp taschreg $";
3	greg	1.1	#endif
4			/*
5			* raytrace.c - routines for tracing and shading rays.
6			*
7	greg	2.34	* External symbols declared in ray.h
8			*/
9
10	greg	2.35	#include "copyright.h"
11	greg	1.1
12			#include "ray.h"
13	schorsch	2.45	#include "source.h"
14	greg	1.1	#include "otypes.h"
15	greg	1.15	#include "otspecial.h"
16	greg	2.51	#include "random.h"
17	greg	2.66	#include "pmap.h"
18	greg	1.15
19	greg	2.3	#define MAXCSET ((MAXSET+1)2-1) / maximum check set size */
20
21	greg	2.60	RNUMBER raynum = 0; /* next unique ray number */
22			RNUMBER nrays = 0; /* number of calls to localhit */
23	greg	1.1
24	schorsch	2.40	static RREAL Lambfa[5] = {PI, PI, PI, 0.0, 0.0};
25	greg	1.15	OBJREC Lamb = {
26			OVOID, MAT_PLASTIC, "Lambertian",
27	greg	2.57	{NULL, Lambfa, 0, 5}, NULL
28	greg	1.15	}; /* a Lambertian surface */
29
30	greg	2.17	OBJREC Aftplane; /* aft clipping plane object */
31	greg	2.16
32	schorsch	2.45	#define RAYHIT (-1) /* return value for intercepted ray */
33	greg	2.5
34	schorsch	2.45	static int raymove(FVECT pos, OBJECT cxs, int dirf, RAY r, CUBE *cu);
35			static int checkhit(RAY r, CUBE cu, OBJECT *cxs);
36			static void checkset(OBJECT os, OBJECT cs);
37	greg	1.1
38
39	greg	2.65	int
40	schorsch	2.45	rayorigin( /* start new ray from old one */
41	greg	2.49	RAY *r,
42	schorsch	2.45	int rt,
43	greg	2.49	const RAY *ro,
44			const COLOR rc
45	schorsch	2.45	)
46	greg	1.1	{
47	greg	2.49	double rw, re;
48			/* assign coefficient/weight */
49			if (rc == NULL) {
50			rw = 1.0;
51			setcolor(r->rcoef, 1., 1., 1.);
52			} else {
53			rw = intens(rc);
54			if (rc != r->rcoef)
55			copycolor(r->rcoef, rc);
56			}
57	greg	1.1	if ((r->parent = ro) == NULL) { /* primary ray */
58			r->rlvl = 0;
59			r->rweight = rw;
60			r->crtype = r->rtype = rt;
61			r->rsrc = -1;
62			r->clipset = NULL;
63	greg	2.50	r->revf = raytrace;
64	greg	2.23	copycolor(r->cext, cextinction);
65	greg	2.26	copycolor(r->albedo, salbedo);
66	greg	2.23	r->gecc = seccg;
67			r->slights = NULL;
68	greg	1.1	} else { /* spawned ray */
69	greg	2.49	if (ro->rot >= FHUGE) {
70			memset(r, 0, sizeof(RAY));
71			return(-1); /* illegal continuation */
72			}
73	greg	1.1	r->rlvl = ro->rlvl;
74			if (rt & RAYREFL) {
75			r->rlvl++;
76			r->rsrc = -1;
77			r->clipset = ro->clipset;
78	greg	2.22	r->rmax = 0.0;
79	greg	1.1	} else {
80			r->rsrc = ro->rsrc;
81			r->clipset = ro->newcset;
82	greg	2.22	r->rmax = ro->rmax <= FTINY ? 0.0 : ro->rmax - ro->rot;
83	greg	1.1	}
84	greg	2.50	r->revf = ro->revf;
85	greg	2.23	copycolor(r->cext, ro->cext);
86	greg	2.26	copycolor(r->albedo, ro->albedo);
87	greg	2.23	r->gecc = ro->gecc;
88			r->slights = ro->slights;
89	greg	1.1	r->crtype = ro->crtype \| (r->rtype = rt);
90			VCOPY(r->rorg, ro->rop);
91	gwlarson	2.31	r->rweight = ro->rweight * rw;
92	greg	2.49	/* estimate extinction */
93	gwlarson	2.31	re = colval(ro->cext,RED) < colval(ro->cext,GRN) ?
94			colval(ro->cext,RED) : colval(ro->cext,GRN);
95			if (colval(ro->cext,BLU) < re) re = colval(ro->cext,BLU);
96	greg	2.49	re *= ro->rot;
97	schorsch	2.58	if (re > 0.1) {
98			if (re > 92.) {
99	greg	2.53	r->rweight = 0.0;
100	schorsch	2.58	} else {
101	greg	2.53	r->rweight *= exp(-re);
102	schorsch	2.58	}
103			}
104	greg	1.1	}
105	greg	1.22	rayclear(r);
106	greg	2.53	if (r->rweight <= 0.0) /* check for expiration */
107			return(-1);
108	greg	2.52	if (r->crtype & SHADOW) /* shadow commitment */
109			return(0);
110	greg	2.51	if (maxdepth <= 0 && rc != NULL) { /* Russian roulette */
111			if (minweight <= 0.0)
112			error(USER, "zero ray weight in Russian roulette");
113			if (maxdepth < 0 && r->rlvl > -maxdepth)
114			return(-1); /* upper reflection limit */
115			if (r->rweight >= minweight)
116			return(0);
117	greg	2.55	if (frandom() > r->rweight/minweight)
118	greg	2.51	return(-1);
119			rw = minweight/r->rweight; /* promote survivor */
120			scalecolor(r->rcoef, rw);
121			r->rweight = minweight;
122			return(0);
123			}
124	greg	2.64	return(r->rweight >= minweight && r->rlvl <= abs(maxdepth) ? 0 : -1);
125	greg	1.22	}
126
127
128	greg	2.65	void
129	schorsch	2.45	rayclear( /* clear a ray for (re)evaluation */
130	greg	2.64	RAY *r
131	schorsch	2.45	)
132	greg	1.22	{
133	greg	1.20	r->rno = raynum++;
134	greg	1.1	r->newcset = r->clipset;
135	greg	2.36	r->hitf = rayhit;
136	greg	2.28	r->robj = OVOID;
137	greg	2.17	r->ro = NULL;
138	greg	2.34	r->rox = NULL;
139	gregl	2.29	r->rt = r->rot = FHUGE;
140	greg	1.1	r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
141	greg	2.37	r->uv[0] = r->uv[1] = 0.0;
142	greg	1.1	setcolor(r->pcol, 1.0, 1.0, 1.0);
143			setcolor(r->rcol, 0.0, 0.0, 0.0);
144			}
145
146
147	greg	2.65	void
148	greg	2.50	raytrace( /* trace a ray and compute its value */
149	schorsch	2.45	RAY *r
150			)
151	greg	1.1	{
152	greg	1.15	if (localhit(r, &thescene))
153	greg	2.24	raycont(r); /* hit local surface, evaluate */
154	greg	2.16	else if (r->ro == &Aftplane) {
155	greg	2.23	r->ro = NULL; /* hit aft clipping plane */
156	greg	2.16	r->rot = FHUGE;
157			} else if (sourcehit(r))
158	greg	2.24	rayshade(r, r->ro->omod); /* distant source */
159	greg	1.1
160			if (trace != NULL)
161			(trace)(r); / trace execution */
162	greg	2.49
163			rayparticipate(r); /* for participating medium */
164	greg	1.1	}
165
166
167	greg	2.65	void
168	schorsch	2.45	raycont( /* check for clipped object and continue */
169	greg	2.64	RAY *r
170	schorsch	2.45	)
171	greg	1.8	{
172	greg	2.7	if ((r->clipset != NULL && inset(r->clipset, r->ro->omod)) \|\|
173	greg	2.24	!rayshade(r, r->ro->omod))
174	greg	1.8	raytrans(r);
175			}
176
177
178	greg	2.65	void
179	schorsch	2.45	raytrans( /* transmit ray as is */
180	greg	2.64	RAY *r
181	schorsch	2.45	)
182	greg	1.1	{
183			RAY tr;
184
185	greg	2.49	if (rayorigin(&tr, TRANS, r, NULL) == 0) {
186	greg	1.1	VCOPY(tr.rdir, r->rdir);
187			rayvalue(&tr);
188			copycolor(r->rcol, tr.rcol);
189	greg	1.10	r->rt = r->rot + tr.rt;
190	greg	1.1	}
191			}
192
193
194	greg	2.65	int
195	schorsch	2.45	rayshade( /* shade ray r with material mod */
196	greg	2.64	RAY *r,
197	schorsch	2.45	int mod
198			)
199	greg	1.1	{
200	greg	2.64	OBJREC *m;
201	greg	2.47
202	greg	1.19	r->rt = r->rot; /* set effective ray length */
203	greg	2.47	for ( ; mod != OVOID; mod = m->omod) {
204	greg	1.1	m = objptr(mod);
205	greg	1.4	/****** unnecessary test since modifier() is always called
206	greg	1.1	if (!ismodifier(m->otype)) {
207			sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
208			error(USER, errmsg);
209			}
210	greg	1.4	******/
211	greg	1.16	/* hack for irradiance calculation */
212	greg	2.38	if (do_irrad && !(r->crtype & ~(PRIMARY\|TRANS)) &&
213	greg	2.43	m->otype != MAT_CLIP &&
214	greg	2.38	(ofun[m->otype].flags & (T_M\|T_X))) {
215	greg	1.16	if (irr_ignore(m->otype)) {
216			raytrans(r);
217	greg	2.15	return(1);
218	greg	1.16	}
219	greg	1.18	if (!islight(m->otype))
220	greg	1.16	m = &Lamb;
221			}
222	greg	2.47	if ((*ofun[m->otype].funp)(m, r))
223			return(1); /* materials call raytexture() */
224	greg	1.1	}
225	greg	2.47	return(0); /* no material! */
226	greg	2.23	}
227
228
229	greg	2.65	void
230	schorsch	2.45	rayparticipate( /* compute ray medium participation */
231	greg	2.64	RAY *r
232	schorsch	2.45	)
233	greg	2.23	{
234			COLOR ce, ca;
235			double re, ge, be;
236
237			if (intens(r->cext) <= 1./FHUGE)
238			return; /* no medium */
239	greg	2.27	re = r->rot*colval(r->cext,RED);
240			ge = r->rot*colval(r->cext,GRN);
241			be = r->rot*colval(r->cext,BLU);
242	greg	2.26	if (r->crtype & SHADOW) { /* no scattering for sources */
243			re *= 1. - colval(r->albedo,RED);
244			ge *= 1. - colval(r->albedo,GRN);
245			be *= 1. - colval(r->albedo,BLU);
246			}
247	greg	2.49	setcolor(ce, re<=FTINY ? 1. : re>92. ? 0. : exp(-re),
248			ge<=FTINY ? 1. : ge>92. ? 0. : exp(-ge),
249			be<=FTINY ? 1. : be>92. ? 0. : exp(-be));
250			multcolor(r->rcol, ce); /* path extinction */
251	greg	2.26	if (r->crtype & SHADOW \|\| intens(r->albedo) <= FTINY)
252	greg	2.23	return; /* no scattering */
253	greg	2.66
254			/* PMAP: indirect inscattering accounted for by volume photons? */
255			if (!volumePhotonMapping) {
256			setcolor(ca,
257			colval(r->albedo,RED)colval(ambval,RED)(1.-colval(ce,RED)),
258			colval(r->albedo,GRN)colval(ambval,GRN)(1.-colval(ce,GRN)),
259			colval(r->albedo,BLU)colval(ambval,BLU)(1.-colval(ce,BLU)));
260			addcolor(r->rcol, ca); /* ambient in scattering */
261			}
262
263	greg	2.23	srcscatter(r); /* source in scattering */
264	greg	1.1	}
265
266
267	greg	2.65	void
268	schorsch	2.45	raytexture( /* get material modifiers */
269			RAY *r,
270			OBJECT mod
271			)
272	greg	1.1	{
273	greg	2.64	OBJREC *m;
274	greg	1.1	/* execute textures and patterns */
275			for ( ; mod != OVOID; mod = m->omod) {
276			m = objptr(mod);
277	greg	2.9	/****** unnecessary test since modifier() is always called
278			if (!ismodifier(m->otype)) {
279	greg	1.1	sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
280			error(USER, errmsg);
281			}
282	greg	2.9	******/
283	greg	2.20	if ((*ofun[m->otype].funp)(m, r)) {
284			sprintf(errmsg, "conflicting material \"%s\"",
285			m->oname);
286			objerror(r->ro, USER, errmsg);
287			}
288	greg	1.1	}
289			}
290
291
292	greg	2.65	int
293	schorsch	2.45	raymixture( /* mix modifiers */
294	greg	2.64	RAY *r,
295	schorsch	2.45	OBJECT fore,
296			OBJECT back,
297			double coef
298			)
299	greg	1.1	{
300	greg	2.9	RAY fr, br;
301			int foremat, backmat;
302	greg	2.64	int i;
303	greg	2.24	/* bound coefficient */
304	greg	1.1	if (coef > 1.0)
305			coef = 1.0;
306			else if (coef < 0.0)
307			coef = 0.0;
308	greg	2.13	/* compute foreground and background */
309	greg	2.24	foremat = backmat = 0;
310	greg	2.9	/* foreground */
311	schorsch	2.41	fr = *r;
312	greg	2.54	if (coef > FTINY) {
313	greg	2.59	fr.rweight *= coef;
314	greg	2.54	scalecolor(fr.rcoef, coef);
315	greg	2.9	foremat = rayshade(&fr, fore);
316	greg	2.54	}
317	greg	2.9	/* background */
318	schorsch	2.41	br = *r;
319	greg	2.54	if (coef < 1.0-FTINY) {
320	greg	2.59	br.rweight *= 1.0-coef;
321	greg	2.54	scalecolor(br.rcoef, 1.0-coef);
322	greg	2.9	backmat = rayshade(&br, back);
323	greg	2.54	}
324	greg	2.24	/* check for transparency */
325	schorsch	2.41	if (backmat ^ foremat) {
326	gwlarson	2.33	if (backmat && coef > FTINY)
327	greg	2.24	raytrans(&fr);
328	gwlarson	2.33	else if (foremat && coef < 1.0-FTINY)
329	greg	2.24	raytrans(&br);
330	schorsch	2.41	}
331	greg	2.12	/* mix perturbations */
332	greg	1.1	for (i = 0; i < 3; i++)
333	greg	2.12	r->pert[i] = coeffr.pert[i] + (1.0-coef)br.pert[i];
334			/* mix pattern colors */
335	greg	2.9	scalecolor(fr.pcol, coef);
336			scalecolor(br.pcol, 1.0-coef);
337	greg	2.12	copycolor(r->pcol, fr.pcol);
338			addcolor(r->pcol, br.pcol);
339	greg	2.24	/* return value tells if material */
340			if (!foremat & !backmat)
341			return(0);
342	greg	2.12	/* mix returned ray values */
343	greg	2.24	scalecolor(fr.rcol, coef);
344			scalecolor(br.rcol, 1.0-coef);
345			copycolor(r->rcol, fr.rcol);
346			addcolor(r->rcol, br.rcol);
347			r->rt = bright(fr.rcol) > bright(br.rcol) ? fr.rt : br.rt;
348			return(1);
349	greg	1.1	}
350
351
352	greg	2.65	double
353	schorsch	2.45	raydist( /* compute (cumulative) ray distance */
354	greg	2.64	const RAY *r,
355			int flags
356	schorsch	2.45	)
357	greg	2.21	{
358			double sum = 0.0;
359
360			while (r != NULL && r->crtype&flags) {
361			sum += r->rot;
362			r = r->parent;
363			}
364			return(sum);
365			}
366
367
368	greg	2.65	void
369	greg	2.49	raycontrib( /* compute (cumulative) ray contribution */
370	greg	2.63	RREAL rc[3],
371	greg	2.49	const RAY *r,
372			int flags
373			)
374			{
375	greg	2.52	double eext[3];
376			int i;
377
378			eext[0] = eext[1] = eext[2] = 0.;
379			rc[0] = rc[1] = rc[2] = 1.;
380	greg	2.49
381			while (r != NULL && r->crtype&flags) {
382	greg	2.52	for (i = 3; i--; ) {
383			rc[i] *= colval(r->rcoef,i);
384			eext[i] += r->rot * colval(r->cext,i);
385			}
386	greg	2.49	r = r->parent;
387			}
388	greg	2.52	for (i = 3; i--; )
389			rc[i] *= (eext[i] <= FTINY) ? 1. :
390	greg	2.53	(eext[i] > 92.) ? 0. : exp(-eext[i]);
391	greg	2.49	}
392
393
394	greg	2.65	double
395	schorsch	2.45	raynormal( /* compute perturbed normal for ray */
396			FVECT norm,
397	greg	2.64	RAY *r
398	schorsch	2.45	)
399	greg	1.1	{
400			double newdot;
401	greg	2.64	int i;
402	greg	1.1
403			/* The perturbation is added to the surface normal to obtain
404			* the new normal. If the new normal would affect the surface
405			* orientation wrt. the ray, a correction is made. The method is
406			* still fraught with problems since reflected rays and similar
407			* directions calculated from the surface normal may spawn rays behind
408			* the surface. The only solution is to curb textures at high
409	greg	1.9	* incidence (namely, keep DOT(rdir,pert) < Rdot).
410	greg	1.1	*/
411
412			for (i = 0; i < 3; i++)
413			norm[i] = r->ron[i] + r->pert[i];
414
415			if (normalize(norm) == 0.0) {
416			objerror(r->ro, WARNING, "illegal normal perturbation");
417			VCOPY(norm, r->ron);
418			return(r->rod);
419			}
420			newdot = -DOT(norm, r->rdir);
421			if ((newdot > 0.0) != (r->rod > 0.0)) { /* fix orientation */
422			for (i = 0; i < 3; i++)
423			norm[i] += 2.0newdotr->rdir[i];
424			newdot = -newdot;
425			}
426			return(newdot);
427	greg	1.12	}
428
429
430	greg	2.65	void
431	schorsch	2.45	newrayxf( /* get new tranformation matrix for ray */
432			RAY *r
433			)
434	greg	1.12	{
435			static struct xfn {
436			struct xfn *next;
437			FULLXF xf;
438			} xfseed = { &xfseed }, *xflast = &xfseed;
439	greg	2.64	struct xfn *xp;
440			const RAY *rp;
441	greg	1.12
442			/*
443			* Search for transform in circular list that
444			* has no associated ray in the tree.
445			*/
446			xp = xflast;
447			for (rp = r->parent; rp != NULL; rp = rp->parent)
448			if (rp->rox == &xp->xf) { /* xp in use */
449			xp = xp->next; /* move to next */
450			if (xp == xflast) { /* need new one */
451	greg	2.64	xp = (struct xfn *)bmalloc(sizeof(struct xfn));
452	greg	1.12	if (xp == NULL)
453			error(SYSTEM,
454			"out of memory in newrayxf");
455			/* insert in list */
456			xp->next = xflast->next;
457			xflast->next = xp;
458			break; /* we're done */
459			}
460			rp = r; /* start check over */
461			}
462			/* got it */
463			r->rox = &xp->xf;
464			xflast = xp;
465	greg	1.1	}
466
467
468	greg	2.65	void
469	schorsch	2.45	flipsurface( /* reverse surface orientation */
470	greg	2.64	RAY *r
471	schorsch	2.45	)
472	greg	1.1	{
473			r->rod = -r->rod;
474			r->ron[0] = -r->ron[0];
475			r->ron[1] = -r->ron[1];
476			r->ron[2] = -r->ron[2];
477			r->pert[0] = -r->pert[0];
478			r->pert[1] = -r->pert[1];
479			r->pert[2] = -r->pert[2];
480			}
481
482
483	greg	2.65	void
484	schorsch	2.45	rayhit( /* standard ray hit test */
485			OBJECT *oset,
486			RAY *r
487			)
488	greg	2.36	{
489			OBJREC *o;
490			int i;
491
492			for (i = oset[0]; i > 0; i--) {
493			o = objptr(oset[i]);
494			if ((*ofun[o->otype].funp)(o, r))
495			r->robj = oset[i];
496			}
497			}
498
499
500	greg	2.65	int
501	schorsch	2.45	localhit( /* check for hit in the octree */
502	greg	2.64	RAY *r,
503			CUBE *scene
504	schorsch	2.45	)
505	greg	1.1	{
506	greg	2.3	OBJECT cxset[MAXCSET+1]; /* set of checked objects */
507	greg	1.1	FVECT curpos; /* current cube position */
508	greg	1.11	int sflags; /* sign flags */
509	greg	1.1	double t, dt;
510	greg	2.64	int i;
511	greg	1.1
512	greg	1.21	nrays++; /* increment trace counter */
513	greg	1.11	sflags = 0;
514	greg	1.1	for (i = 0; i < 3; i++) {
515			curpos[i] = r->rorg[i];
516	greg	2.8	if (r->rdir[i] > 1e-7)
517	greg	1.11	sflags \|= 1 << i;
518	greg	2.8	else if (r->rdir[i] < -1e-7)
519	greg	1.11	sflags \|= 0x10 << i;
520	greg	1.1	}
521	greg	2.61	if (!sflags) {
522			error(WARNING, "zero ray direction in localhit");
523			return(0);
524			}
525	greg	2.17	/* start off assuming nothing hit */
526			if (r->rmax > FTINY) { /* except aft plane if one */
527			r->ro = &Aftplane;
528			r->rot = r->rmax;
529	greg	2.62	VSUM(r->rop, r->rorg, r->rdir, r->rot);
530	greg	2.17	}
531			/* find global cube entrance point */
532	greg	1.1	t = 0.0;
533			if (!incube(scene, curpos)) {
534			/* find distance to entry */
535			for (i = 0; i < 3; i++) {
536			/* plane in our direction */
537	greg	1.11	if (sflags & 1<<i)
538	greg	1.1	dt = scene->cuorg[i];
539	greg	1.11	else if (sflags & 0x10<<i)
540	greg	1.1	dt = scene->cuorg[i] + scene->cusize;
541			else
542			continue;
543			/* distance to the plane */
544			dt = (dt - r->rorg[i])/r->rdir[i];
545			if (dt > t)
546			t = dt; /* farthest face is the one */
547			}
548			t += FTINY; /* fudge to get inside cube */
549	greg	2.17	if (t >= r->rot) /* clipped already */
550			return(0);
551	greg	1.1	/* advance position */
552	greg	2.62	VSUM(curpos, curpos, r->rdir, t);
553	greg	1.1
554			if (!incube(scene, curpos)) /* non-intersecting ray */
555			return(0);
556			}
557	greg	2.3	cxset[0] = 0;
558	greg	2.19	raymove(curpos, cxset, sflags, r, scene);
559	schorsch	2.42	return((r->ro != NULL) & (r->ro != &Aftplane));
560	greg	1.1	}
561
562
563			static int
564	schorsch	2.45	raymove( /* check for hit as we move */
565			FVECT pos, /* current position, modified herein */
566			OBJECT cxs, / checked objects, modified by checkhit */
567			int dirf, /* direction indicators to speed tests */
568	greg	2.64	RAY *r,
569			CUBE *cu
570	schorsch	2.45	)
571	greg	1.1	{
572			int ax;
573			double dt, t;
574
575			if (istree(cu->cutree)) { /* recurse on subcubes */
576			CUBE cukid;
577	greg	2.64	int br, sgn;
578	greg	1.1
579			cukid.cusize = cu->cusize * 0.5; /* find subcube */
580			VCOPY(cukid.cuorg, cu->cuorg);
581			br = 0;
582			if (pos[0] >= cukid.cuorg[0]+cukid.cusize) {
583			cukid.cuorg[0] += cukid.cusize;
584			br \|= 1;
585			}
586			if (pos[1] >= cukid.cuorg[1]+cukid.cusize) {
587			cukid.cuorg[1] += cukid.cusize;
588			br \|= 2;
589			}
590			if (pos[2] >= cukid.cuorg[2]+cukid.cusize) {
591			cukid.cuorg[2] += cukid.cusize;
592			br \|= 4;
593			}
594			for ( ; ; ) {
595			cukid.cutree = octkid(cu->cutree, br);
596	greg	2.3	if ((ax = raymove(pos,cxs,dirf,r,&cukid)) == RAYHIT)
597	greg	1.1	return(RAYHIT);
598			sgn = 1 << ax;
599	greg	1.11	if (sgn & dirf) /* positive axis? */
600	greg	1.1	if (sgn & br)
601			return(ax); /* overflow */
602			else {
603			cukid.cuorg[ax] += cukid.cusize;
604			br \|= sgn;
605			}
606	greg	1.11	else
607			if (sgn & br) {
608			cukid.cuorg[ax] -= cukid.cusize;
609			br &= ~sgn;
610			} else
611			return(ax); /* underflow */
612	greg	1.1	}
613			/NOTREACHED/
614			}
615	greg	2.18	if (isfull(cu->cutree)) {
616			if (checkhit(r, cu, cxs))
617			return(RAYHIT);
618			} else if (r->ro == &Aftplane && incube(cu, r->rop))
619	greg	1.1	return(RAYHIT);
620			/* advance to next cube */
621	greg	1.11	if (dirf&0x11) {
622			dt = dirf&1 ? cu->cuorg[0] + cu->cusize : cu->cuorg[0];
623	greg	1.1	t = (dt - pos[0])/r->rdir[0];
624			ax = 0;
625			} else
626			t = FHUGE;
627	greg	1.11	if (dirf&0x22) {
628			dt = dirf&2 ? cu->cuorg[1] + cu->cusize : cu->cuorg[1];
629	greg	1.1	dt = (dt - pos[1])/r->rdir[1];
630			if (dt < t) {
631			t = dt;
632			ax = 1;
633			}
634			}
635	greg	1.11	if (dirf&0x44) {
636			dt = dirf&4 ? cu->cuorg[2] + cu->cusize : cu->cuorg[2];
637	greg	1.1	dt = (dt - pos[2])/r->rdir[2];
638			if (dt < t) {
639			t = dt;
640			ax = 2;
641			}
642			}
643	greg	2.62	VSUM(pos, pos, r->rdir, t);
644	greg	1.1	return(ax);
645			}
646
647
648	greg	2.34	static int
649	schorsch	2.45	checkhit( /* check for hit in full cube */
650	greg	2.64	RAY *r,
651	schorsch	2.45	CUBE *cu,
652			OBJECT *cxs
653			)
654	greg	1.1	{
655			OBJECT oset[MAXSET+1];
656
657			objset(oset, cu->cutree);
658	greg	2.36	checkset(oset, cxs); /* avoid double-checking */
659
660			(r->hitf)(oset, r); / test for hit in set */
661
662			if (r->robj == OVOID)
663	greg	1.1	return(0); /* no scores yet */
664
665			return(incube(cu, r->rop)); /* hit OK if in current cube */
666	greg	2.2	}
667
668
669	greg	2.34	static void
670	schorsch	2.45	checkset( /* modify checked set and set to check */
671	greg	2.64	OBJECT os, / os' = os - cs */
672			OBJECT cs / cs' = cs + os */
673	schorsch	2.45	)
674	greg	2.2	{
675			OBJECT cset[MAXCSET+MAXSET+1];
676	greg	2.64	int i, j;
677	greg	2.3	int k;
678	greg	2.2	/* copy os in place, cset <- cs */
679			cset[0] = 0;
680			k = 0;
681			for (i = j = 1; i <= os[0]; i++) {
682			while (j <= cs[0] && cs[j] < os[i])
683			cset[++cset[0]] = cs[j++];
684			if (j > cs[0] \|\| os[i] != cs[j]) { /* object to check */
685			os[++k] = os[i];
686			cset[++cset[0]] = os[i];
687			}
688			}
689	greg	2.3	if (!(os[0] = k)) /* new "to check" set size */
690			return; /* special case */
691	greg	2.2	while (j <= cs[0]) /* get the rest of cs */
692			cset[++cset[0]] = cs[j++];
693	greg	2.3	if (cset[0] > MAXCSET) /* truncate "checked" set if nec. */
694	greg	2.2	cset[0] = MAXCSET;
695	greg	2.3	/* setcopy(cs, cset); / / copy cset back to cs */
696			os = cset;
697			for (i = os[0]; i-- >= 0; )
698			cs++ = os++;
699	greg	1.1	}