src/rt/raytrace.c

#ifndef lint
static const char RCSid[] = "$Id: raytrace.c,v 2.64 2012/06/01 19:17:17 greg Exp $";
#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"

#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 */
        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:	2.65
Committed:	Wed Feb 19 14:12:48 2014 UTC (10 years, 2 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad4R2P2, rad4R2, rad4R2P1
Changes since 2.64:	+17 -17 lines
Log Message:	Eliminated superfluous extern declarations
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.65	static const char RCSid[] = "$Id: raytrace.c,v 2.64 2012/06/01 19:17:17 greg Exp $";
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	1.15
18	greg	2.3	#define MAXCSET ((MAXSET+1)2-1) / maximum check set size */
19
20	greg	2.60	RNUMBER raynum = 0; /* next unique ray number */
21			RNUMBER nrays = 0; /* number of calls to localhit */
22	greg	1.1
23	schorsch	2.40	static RREAL Lambfa[5] = {PI, PI, PI, 0.0, 0.0};
24	greg	1.15	OBJREC Lamb = {
25			OVOID, MAT_PLASTIC, "Lambertian",
26	greg	2.57	{NULL, Lambfa, 0, 5}, NULL
27	greg	1.15	}; /* a Lambertian surface */
28
29	greg	2.17	OBJREC Aftplane; /* aft clipping plane object */
30	greg	2.16
31	schorsch	2.45	#define RAYHIT (-1) /* return value for intercepted ray */
32	greg	2.5
33	schorsch	2.45	static int raymove(FVECT pos, OBJECT cxs, int dirf, RAY r, CUBE *cu);
34			static int checkhit(RAY r, CUBE cu, OBJECT *cxs);
35			static void checkset(OBJECT os, OBJECT cs);
36	greg	1.1
37
38	greg	2.65	int
39	schorsch	2.45	rayorigin( /* start new ray from old one */
40	greg	2.49	RAY *r,
41	schorsch	2.45	int rt,
42	greg	2.49	const RAY *ro,
43			const COLOR rc
44	schorsch	2.45	)
45	greg	1.1	{
46	greg	2.49	double rw, re;
47			/* assign coefficient/weight */
48			if (rc == NULL) {
49			rw = 1.0;
50			setcolor(r->rcoef, 1., 1., 1.);
51			} else {
52			rw = intens(rc);
53			if (rc != r->rcoef)
54			copycolor(r->rcoef, rc);
55			}
56	greg	1.1	if ((r->parent = ro) == NULL) { /* primary ray */
57			r->rlvl = 0;
58			r->rweight = rw;
59			r->crtype = r->rtype = rt;
60			r->rsrc = -1;
61			r->clipset = NULL;
62	greg	2.50	r->revf = raytrace;
63	greg	2.23	copycolor(r->cext, cextinction);
64	greg	2.26	copycolor(r->albedo, salbedo);
65	greg	2.23	r->gecc = seccg;
66			r->slights = NULL;
67	greg	1.1	} else { /* spawned ray */
68	greg	2.49	if (ro->rot >= FHUGE) {
69			memset(r, 0, sizeof(RAY));
70			return(-1); /* illegal continuation */
71			}
72	greg	1.1	r->rlvl = ro->rlvl;
73			if (rt & RAYREFL) {
74			r->rlvl++;
75			r->rsrc = -1;
76			r->clipset = ro->clipset;
77	greg	2.22	r->rmax = 0.0;
78	greg	1.1	} else {
79			r->rsrc = ro->rsrc;
80			r->clipset = ro->newcset;
81	greg	2.22	r->rmax = ro->rmax <= FTINY ? 0.0 : ro->rmax - ro->rot;
82	greg	1.1	}
83	greg	2.50	r->revf = ro->revf;
84	greg	2.23	copycolor(r->cext, ro->cext);
85	greg	2.26	copycolor(r->albedo, ro->albedo);
86	greg	2.23	r->gecc = ro->gecc;
87			r->slights = ro->slights;
88	greg	1.1	r->crtype = ro->crtype \| (r->rtype = rt);
89			VCOPY(r->rorg, ro->rop);
90	gwlarson	2.31	r->rweight = ro->rweight * rw;
91	greg	2.49	/* estimate extinction */
92	gwlarson	2.31	re = colval(ro->cext,RED) < colval(ro->cext,GRN) ?
93			colval(ro->cext,RED) : colval(ro->cext,GRN);
94			if (colval(ro->cext,BLU) < re) re = colval(ro->cext,BLU);
95	greg	2.49	re *= ro->rot;
96	schorsch	2.58	if (re > 0.1) {
97			if (re > 92.) {
98	greg	2.53	r->rweight = 0.0;
99	schorsch	2.58	} else {
100	greg	2.53	r->rweight *= exp(-re);
101	schorsch	2.58	}
102			}
103	greg	1.1	}
104	greg	1.22	rayclear(r);
105	greg	2.53	if (r->rweight <= 0.0) /* check for expiration */
106			return(-1);
107	greg	2.52	if (r->crtype & SHADOW) /* shadow commitment */
108			return(0);
109	greg	2.51	if (maxdepth <= 0 && rc != NULL) { /* Russian roulette */
110			if (minweight <= 0.0)
111			error(USER, "zero ray weight in Russian roulette");
112			if (maxdepth < 0 && r->rlvl > -maxdepth)
113			return(-1); /* upper reflection limit */
114			if (r->rweight >= minweight)
115			return(0);
116	greg	2.55	if (frandom() > r->rweight/minweight)
117	greg	2.51	return(-1);
118			rw = minweight/r->rweight; /* promote survivor */
119			scalecolor(r->rcoef, rw);
120			r->rweight = minweight;
121			return(0);
122			}
123	greg	2.64	return(r->rweight >= minweight && r->rlvl <= abs(maxdepth) ? 0 : -1);
124	greg	1.22	}
125
126
127	greg	2.65	void
128	schorsch	2.45	rayclear( /* clear a ray for (re)evaluation */
129	greg	2.64	RAY *r
130	schorsch	2.45	)
131	greg	1.22	{
132	greg	1.20	r->rno = raynum++;
133	greg	1.1	r->newcset = r->clipset;
134	greg	2.36	r->hitf = rayhit;
135	greg	2.28	r->robj = OVOID;
136	greg	2.17	r->ro = NULL;
137	greg	2.34	r->rox = NULL;
138	gregl	2.29	r->rt = r->rot = FHUGE;
139	greg	1.1	r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
140	greg	2.37	r->uv[0] = r->uv[1] = 0.0;
141	greg	1.1	setcolor(r->pcol, 1.0, 1.0, 1.0);
142			setcolor(r->rcol, 0.0, 0.0, 0.0);
143			}
144
145
146	greg	2.65	void
147	greg	2.50	raytrace( /* trace a ray and compute its value */
148	schorsch	2.45	RAY *r
149			)
150	greg	1.1	{
151	greg	1.15	if (localhit(r, &thescene))
152	greg	2.24	raycont(r); /* hit local surface, evaluate */
153	greg	2.16	else if (r->ro == &Aftplane) {
154	greg	2.23	r->ro = NULL; /* hit aft clipping plane */
155	greg	2.16	r->rot = FHUGE;
156			} else if (sourcehit(r))
157	greg	2.24	rayshade(r, r->ro->omod); /* distant source */
158	greg	1.1
159			if (trace != NULL)
160			(trace)(r); / trace execution */
161	greg	2.49
162			rayparticipate(r); /* for participating medium */
163	greg	1.1	}
164
165
166	greg	2.65	void
167	schorsch	2.45	raycont( /* check for clipped object and continue */
168	greg	2.64	RAY *r
169	schorsch	2.45	)
170	greg	1.8	{
171	greg	2.7	if ((r->clipset != NULL && inset(r->clipset, r->ro->omod)) \|\|
172	greg	2.24	!rayshade(r, r->ro->omod))
173	greg	1.8	raytrans(r);
174			}
175
176
177	greg	2.65	void
178	schorsch	2.45	raytrans( /* transmit ray as is */
179	greg	2.64	RAY *r
180	schorsch	2.45	)
181	greg	1.1	{
182			RAY tr;
183
184	greg	2.49	if (rayorigin(&tr, TRANS, r, NULL) == 0) {
185	greg	1.1	VCOPY(tr.rdir, r->rdir);
186			rayvalue(&tr);
187			copycolor(r->rcol, tr.rcol);
188	greg	1.10	r->rt = r->rot + tr.rt;
189	greg	1.1	}
190			}
191
192
193	greg	2.65	int
194	schorsch	2.45	rayshade( /* shade ray r with material mod */
195	greg	2.64	RAY *r,
196	schorsch	2.45	int mod
197			)
198	greg	1.1	{
199	greg	2.64	OBJREC *m;
200	greg	2.47
201	greg	1.19	r->rt = r->rot; /* set effective ray length */
202	greg	2.47	for ( ; mod != OVOID; mod = m->omod) {
203	greg	1.1	m = objptr(mod);
204	greg	1.4	/****** unnecessary test since modifier() is always called
205	greg	1.1	if (!ismodifier(m->otype)) {
206			sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
207			error(USER, errmsg);
208			}
209	greg	1.4	******/
210	greg	1.16	/* hack for irradiance calculation */
211	greg	2.38	if (do_irrad && !(r->crtype & ~(PRIMARY\|TRANS)) &&
212	greg	2.43	m->otype != MAT_CLIP &&
213	greg	2.38	(ofun[m->otype].flags & (T_M\|T_X))) {
214	greg	1.16	if (irr_ignore(m->otype)) {
215			raytrans(r);
216	greg	2.15	return(1);
217	greg	1.16	}
218	greg	1.18	if (!islight(m->otype))
219	greg	1.16	m = &Lamb;
220			}
221	greg	2.47	if ((*ofun[m->otype].funp)(m, r))
222			return(1); /* materials call raytexture() */
223	greg	1.1	}
224	greg	2.47	return(0); /* no material! */
225	greg	2.23	}
226
227
228	greg	2.65	void
229	schorsch	2.45	rayparticipate( /* compute ray medium participation */
230	greg	2.64	RAY *r
231	schorsch	2.45	)
232	greg	2.23	{
233			COLOR ce, ca;
234			double re, ge, be;
235
236			if (intens(r->cext) <= 1./FHUGE)
237			return; /* no medium */
238	greg	2.27	re = r->rot*colval(r->cext,RED);
239			ge = r->rot*colval(r->cext,GRN);
240			be = r->rot*colval(r->cext,BLU);
241	greg	2.26	if (r->crtype & SHADOW) { /* no scattering for sources */
242			re *= 1. - colval(r->albedo,RED);
243			ge *= 1. - colval(r->albedo,GRN);
244			be *= 1. - colval(r->albedo,BLU);
245			}
246	greg	2.49	setcolor(ce, re<=FTINY ? 1. : re>92. ? 0. : exp(-re),
247			ge<=FTINY ? 1. : ge>92. ? 0. : exp(-ge),
248			be<=FTINY ? 1. : be>92. ? 0. : exp(-be));
249			multcolor(r->rcol, ce); /* path extinction */
250	greg	2.26	if (r->crtype & SHADOW \|\| intens(r->albedo) <= FTINY)
251	greg	2.23	return; /* no scattering */
252	greg	2.26	setcolor(ca,
253			colval(r->albedo,RED)colval(ambval,RED)(1.-colval(ce,RED)),
254			colval(r->albedo,GRN)colval(ambval,GRN)(1.-colval(ce,GRN)),
255			colval(r->albedo,BLU)colval(ambval,BLU)(1.-colval(ce,BLU)));
256	greg	2.23	addcolor(r->rcol, ca); /* ambient in scattering */
257			srcscatter(r); /* source in scattering */
258	greg	1.1	}
259
260
261	greg	2.65	void
262	schorsch	2.45	raytexture( /* get material modifiers */
263			RAY *r,
264			OBJECT mod
265			)
266	greg	1.1	{
267	greg	2.64	OBJREC *m;
268	greg	1.1	/* execute textures and patterns */
269			for ( ; mod != OVOID; mod = m->omod) {
270			m = objptr(mod);
271	greg	2.9	/****** unnecessary test since modifier() is always called
272			if (!ismodifier(m->otype)) {
273	greg	1.1	sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
274			error(USER, errmsg);
275			}
276	greg	2.9	******/
277	greg	2.20	if ((*ofun[m->otype].funp)(m, r)) {
278			sprintf(errmsg, "conflicting material \"%s\"",
279			m->oname);
280			objerror(r->ro, USER, errmsg);
281			}
282	greg	1.1	}
283			}
284
285
286	greg	2.65	int
287	schorsch	2.45	raymixture( /* mix modifiers */
288	greg	2.64	RAY *r,
289	schorsch	2.45	OBJECT fore,
290			OBJECT back,
291			double coef
292			)
293	greg	1.1	{
294	greg	2.9	RAY fr, br;
295			int foremat, backmat;
296	greg	2.64	int i;
297	greg	2.24	/* bound coefficient */
298	greg	1.1	if (coef > 1.0)
299			coef = 1.0;
300			else if (coef < 0.0)
301			coef = 0.0;
302	greg	2.13	/* compute foreground and background */
303	greg	2.24	foremat = backmat = 0;
304	greg	2.9	/* foreground */
305	schorsch	2.41	fr = *r;
306	greg	2.54	if (coef > FTINY) {
307	greg	2.59	fr.rweight *= coef;
308	greg	2.54	scalecolor(fr.rcoef, coef);
309	greg	2.9	foremat = rayshade(&fr, fore);
310	greg	2.54	}
311	greg	2.9	/* background */
312	schorsch	2.41	br = *r;
313	greg	2.54	if (coef < 1.0-FTINY) {
314	greg	2.59	br.rweight *= 1.0-coef;
315	greg	2.54	scalecolor(br.rcoef, 1.0-coef);
316	greg	2.9	backmat = rayshade(&br, back);
317	greg	2.54	}
318	greg	2.24	/* check for transparency */
319	schorsch	2.41	if (backmat ^ foremat) {
320	gwlarson	2.33	if (backmat && coef > FTINY)
321	greg	2.24	raytrans(&fr);
322	gwlarson	2.33	else if (foremat && coef < 1.0-FTINY)
323	greg	2.24	raytrans(&br);
324	schorsch	2.41	}
325	greg	2.12	/* mix perturbations */
326	greg	1.1	for (i = 0; i < 3; i++)
327	greg	2.12	r->pert[i] = coeffr.pert[i] + (1.0-coef)br.pert[i];
328			/* mix pattern colors */
329	greg	2.9	scalecolor(fr.pcol, coef);
330			scalecolor(br.pcol, 1.0-coef);
331	greg	2.12	copycolor(r->pcol, fr.pcol);
332			addcolor(r->pcol, br.pcol);
333	greg	2.24	/* return value tells if material */
334			if (!foremat & !backmat)
335			return(0);
336	greg	2.12	/* mix returned ray values */
337	greg	2.24	scalecolor(fr.rcol, coef);
338			scalecolor(br.rcol, 1.0-coef);
339			copycolor(r->rcol, fr.rcol);
340			addcolor(r->rcol, br.rcol);
341			r->rt = bright(fr.rcol) > bright(br.rcol) ? fr.rt : br.rt;
342			return(1);
343	greg	1.1	}
344
345
346	greg	2.65	double
347	schorsch	2.45	raydist( /* compute (cumulative) ray distance */
348	greg	2.64	const RAY *r,
349			int flags
350	schorsch	2.45	)
351	greg	2.21	{
352			double sum = 0.0;
353
354			while (r != NULL && r->crtype&flags) {
355			sum += r->rot;
356			r = r->parent;
357			}
358			return(sum);
359			}
360
361
362	greg	2.65	void
363	greg	2.49	raycontrib( /* compute (cumulative) ray contribution */
364	greg	2.63	RREAL rc[3],
365	greg	2.49	const RAY *r,
366			int flags
367			)
368			{
369	greg	2.52	double eext[3];
370			int i;
371
372			eext[0] = eext[1] = eext[2] = 0.;
373			rc[0] = rc[1] = rc[2] = 1.;
374	greg	2.49
375			while (r != NULL && r->crtype&flags) {
376	greg	2.52	for (i = 3; i--; ) {
377			rc[i] *= colval(r->rcoef,i);
378			eext[i] += r->rot * colval(r->cext,i);
379			}
380	greg	2.49	r = r->parent;
381			}
382	greg	2.52	for (i = 3; i--; )
383			rc[i] *= (eext[i] <= FTINY) ? 1. :
384	greg	2.53	(eext[i] > 92.) ? 0. : exp(-eext[i]);
385	greg	2.49	}
386
387
388	greg	2.65	double
389	schorsch	2.45	raynormal( /* compute perturbed normal for ray */
390			FVECT norm,
391	greg	2.64	RAY *r
392	schorsch	2.45	)
393	greg	1.1	{
394			double newdot;
395	greg	2.64	int i;
396	greg	1.1
397			/* The perturbation is added to the surface normal to obtain
398			* the new normal. If the new normal would affect the surface
399			* orientation wrt. the ray, a correction is made. The method is
400			* still fraught with problems since reflected rays and similar
401			* directions calculated from the surface normal may spawn rays behind
402			* the surface. The only solution is to curb textures at high
403	greg	1.9	* incidence (namely, keep DOT(rdir,pert) < Rdot).
404	greg	1.1	*/
405
406			for (i = 0; i < 3; i++)
407			norm[i] = r->ron[i] + r->pert[i];
408
409			if (normalize(norm) == 0.0) {
410			objerror(r->ro, WARNING, "illegal normal perturbation");
411			VCOPY(norm, r->ron);
412			return(r->rod);
413			}
414			newdot = -DOT(norm, r->rdir);
415			if ((newdot > 0.0) != (r->rod > 0.0)) { /* fix orientation */
416			for (i = 0; i < 3; i++)
417			norm[i] += 2.0newdotr->rdir[i];
418			newdot = -newdot;
419			}
420			return(newdot);
421	greg	1.12	}
422
423
424	greg	2.65	void
425	schorsch	2.45	newrayxf( /* get new tranformation matrix for ray */
426			RAY *r
427			)
428	greg	1.12	{
429			static struct xfn {
430			struct xfn *next;
431			FULLXF xf;
432			} xfseed = { &xfseed }, *xflast = &xfseed;
433	greg	2.64	struct xfn *xp;
434			const RAY *rp;
435	greg	1.12
436			/*
437			* Search for transform in circular list that
438			* has no associated ray in the tree.
439			*/
440			xp = xflast;
441			for (rp = r->parent; rp != NULL; rp = rp->parent)
442			if (rp->rox == &xp->xf) { /* xp in use */
443			xp = xp->next; /* move to next */
444			if (xp == xflast) { /* need new one */
445	greg	2.64	xp = (struct xfn *)bmalloc(sizeof(struct xfn));
446	greg	1.12	if (xp == NULL)
447			error(SYSTEM,
448			"out of memory in newrayxf");
449			/* insert in list */
450			xp->next = xflast->next;
451			xflast->next = xp;
452			break; /* we're done */
453			}
454			rp = r; /* start check over */
455			}
456			/* got it */
457			r->rox = &xp->xf;
458			xflast = xp;
459	greg	1.1	}
460
461
462	greg	2.65	void
463	schorsch	2.45	flipsurface( /* reverse surface orientation */
464	greg	2.64	RAY *r
465	schorsch	2.45	)
466	greg	1.1	{
467			r->rod = -r->rod;
468			r->ron[0] = -r->ron[0];
469			r->ron[1] = -r->ron[1];
470			r->ron[2] = -r->ron[2];
471			r->pert[0] = -r->pert[0];
472			r->pert[1] = -r->pert[1];
473			r->pert[2] = -r->pert[2];
474			}
475
476
477	greg	2.65	void
478	schorsch	2.45	rayhit( /* standard ray hit test */
479			OBJECT *oset,
480			RAY *r
481			)
482	greg	2.36	{
483			OBJREC *o;
484			int i;
485
486			for (i = oset[0]; i > 0; i--) {
487			o = objptr(oset[i]);
488			if ((*ofun[o->otype].funp)(o, r))
489			r->robj = oset[i];
490			}
491			}
492
493
494	greg	2.65	int
495	schorsch	2.45	localhit( /* check for hit in the octree */
496	greg	2.64	RAY *r,
497			CUBE *scene
498	schorsch	2.45	)
499	greg	1.1	{
500	greg	2.3	OBJECT cxset[MAXCSET+1]; /* set of checked objects */
501	greg	1.1	FVECT curpos; /* current cube position */
502	greg	1.11	int sflags; /* sign flags */
503	greg	1.1	double t, dt;
504	greg	2.64	int i;
505	greg	1.1
506	greg	1.21	nrays++; /* increment trace counter */
507	greg	1.11	sflags = 0;
508	greg	1.1	for (i = 0; i < 3; i++) {
509			curpos[i] = r->rorg[i];
510	greg	2.8	if (r->rdir[i] > 1e-7)
511	greg	1.11	sflags \|= 1 << i;
512	greg	2.8	else if (r->rdir[i] < -1e-7)
513	greg	1.11	sflags \|= 0x10 << i;
514	greg	1.1	}
515	greg	2.61	if (!sflags) {
516			error(WARNING, "zero ray direction in localhit");
517			return(0);
518			}
519	greg	2.17	/* start off assuming nothing hit */
520			if (r->rmax > FTINY) { /* except aft plane if one */
521			r->ro = &Aftplane;
522			r->rot = r->rmax;
523	greg	2.62	VSUM(r->rop, r->rorg, r->rdir, r->rot);
524	greg	2.17	}
525			/* find global cube entrance point */
526	greg	1.1	t = 0.0;
527			if (!incube(scene, curpos)) {
528			/* find distance to entry */
529			for (i = 0; i < 3; i++) {
530			/* plane in our direction */
531	greg	1.11	if (sflags & 1<<i)
532	greg	1.1	dt = scene->cuorg[i];
533	greg	1.11	else if (sflags & 0x10<<i)
534	greg	1.1	dt = scene->cuorg[i] + scene->cusize;
535			else
536			continue;
537			/* distance to the plane */
538			dt = (dt - r->rorg[i])/r->rdir[i];
539			if (dt > t)
540			t = dt; /* farthest face is the one */
541			}
542			t += FTINY; /* fudge to get inside cube */
543	greg	2.17	if (t >= r->rot) /* clipped already */
544			return(0);
545	greg	1.1	/* advance position */
546	greg	2.62	VSUM(curpos, curpos, r->rdir, t);
547	greg	1.1
548			if (!incube(scene, curpos)) /* non-intersecting ray */
549			return(0);
550			}
551	greg	2.3	cxset[0] = 0;
552	greg	2.19	raymove(curpos, cxset, sflags, r, scene);
553	schorsch	2.42	return((r->ro != NULL) & (r->ro != &Aftplane));
554	greg	1.1	}
555
556
557			static int
558	schorsch	2.45	raymove( /* check for hit as we move */
559			FVECT pos, /* current position, modified herein */
560			OBJECT cxs, / checked objects, modified by checkhit */
561			int dirf, /* direction indicators to speed tests */
562	greg	2.64	RAY *r,
563			CUBE *cu
564	schorsch	2.45	)
565	greg	1.1	{
566			int ax;
567			double dt, t;
568
569			if (istree(cu->cutree)) { /* recurse on subcubes */
570			CUBE cukid;
571	greg	2.64	int br, sgn;
572	greg	1.1
573			cukid.cusize = cu->cusize * 0.5; /* find subcube */
574			VCOPY(cukid.cuorg, cu->cuorg);
575			br = 0;
576			if (pos[0] >= cukid.cuorg[0]+cukid.cusize) {
577			cukid.cuorg[0] += cukid.cusize;
578			br \|= 1;
579			}
580			if (pos[1] >= cukid.cuorg[1]+cukid.cusize) {
581			cukid.cuorg[1] += cukid.cusize;
582			br \|= 2;
583			}
584			if (pos[2] >= cukid.cuorg[2]+cukid.cusize) {
585			cukid.cuorg[2] += cukid.cusize;
586			br \|= 4;
587			}
588			for ( ; ; ) {
589			cukid.cutree = octkid(cu->cutree, br);
590	greg	2.3	if ((ax = raymove(pos,cxs,dirf,r,&cukid)) == RAYHIT)
591	greg	1.1	return(RAYHIT);
592			sgn = 1 << ax;
593	greg	1.11	if (sgn & dirf) /* positive axis? */
594	greg	1.1	if (sgn & br)
595			return(ax); /* overflow */
596			else {
597			cukid.cuorg[ax] += cukid.cusize;
598			br \|= sgn;
599			}
600	greg	1.11	else
601			if (sgn & br) {
602			cukid.cuorg[ax] -= cukid.cusize;
603			br &= ~sgn;
604			} else
605			return(ax); /* underflow */
606	greg	1.1	}
607			/NOTREACHED/
608			}
609	greg	2.18	if (isfull(cu->cutree)) {
610			if (checkhit(r, cu, cxs))
611			return(RAYHIT);
612			} else if (r->ro == &Aftplane && incube(cu, r->rop))
613	greg	1.1	return(RAYHIT);
614			/* advance to next cube */
615	greg	1.11	if (dirf&0x11) {
616			dt = dirf&1 ? cu->cuorg[0] + cu->cusize : cu->cuorg[0];
617	greg	1.1	t = (dt - pos[0])/r->rdir[0];
618			ax = 0;
619			} else
620			t = FHUGE;
621	greg	1.11	if (dirf&0x22) {
622			dt = dirf&2 ? cu->cuorg[1] + cu->cusize : cu->cuorg[1];
623	greg	1.1	dt = (dt - pos[1])/r->rdir[1];
624			if (dt < t) {
625			t = dt;
626			ax = 1;
627			}
628			}
629	greg	1.11	if (dirf&0x44) {
630			dt = dirf&4 ? cu->cuorg[2] + cu->cusize : cu->cuorg[2];
631	greg	1.1	dt = (dt - pos[2])/r->rdir[2];
632			if (dt < t) {
633			t = dt;
634			ax = 2;
635			}
636			}
637	greg	2.62	VSUM(pos, pos, r->rdir, t);
638	greg	1.1	return(ax);
639			}
640
641
642	greg	2.34	static int
643	schorsch	2.45	checkhit( /* check for hit in full cube */
644	greg	2.64	RAY *r,
645	schorsch	2.45	CUBE *cu,
646			OBJECT *cxs
647			)
648	greg	1.1	{
649			OBJECT oset[MAXSET+1];
650
651			objset(oset, cu->cutree);
652	greg	2.36	checkset(oset, cxs); /* avoid double-checking */
653
654			(r->hitf)(oset, r); / test for hit in set */
655
656			if (r->robj == OVOID)
657	greg	1.1	return(0); /* no scores yet */
658
659			return(incube(cu, r->rop)); /* hit OK if in current cube */
660	greg	2.2	}
661
662
663	greg	2.34	static void
664	schorsch	2.45	checkset( /* modify checked set and set to check */
665	greg	2.64	OBJECT os, / os' = os - cs */
666			OBJECT cs / cs' = cs + os */
667	schorsch	2.45	)
668	greg	2.2	{
669			OBJECT cset[MAXCSET+MAXSET+1];
670	greg	2.64	int i, j;
671	greg	2.3	int k;
672	greg	2.2	/* copy os in place, cset <- cs */
673			cset[0] = 0;
674			k = 0;
675			for (i = j = 1; i <= os[0]; i++) {
676			while (j <= cs[0] && cs[j] < os[i])
677			cset[++cset[0]] = cs[j++];
678			if (j > cs[0] \|\| os[i] != cs[j]) { /* object to check */
679			os[++k] = os[i];
680			cset[++cset[0]] = os[i];
681			}
682			}
683	greg	2.3	if (!(os[0] = k)) /* new "to check" set size */
684			return; /* special case */
685	greg	2.2	while (j <= cs[0]) /* get the rest of cs */
686			cset[++cset[0]] = cs[j++];
687	greg	2.3	if (cset[0] > MAXCSET) /* truncate "checked" set if nec. */
688	greg	2.2	cset[0] = MAXCSET;
689	greg	2.3	/* setcopy(cs, cset); / / copy cset back to cs */
690			os = cset;
691			for (i = os[0]; i-- >= 0; )
692			cs++ = os++;
693	greg	1.1	}