src/rt/raytrace.c

#ifndef lint
static const char RCSid[] = "$Id: raytrace.c,v 2.89 2024/07/31 22:29:18 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"
#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 SCOLOR rc
)
{
        double  rw, re;
                                                /* assign coefficient/weight */
        if (rc == NULL) {
                rw = 1.0;
                setscolor(r->rcoef, 1., 1., 1.);
        } else {
                rw = sintens((COLORV *)rc);
                if (rw > 1.0)
                        rw = 1.0;               /* avoid calculation growth */
                if (rc != r->rcoef)
                        copyscolor(r->rcoef, rc);
        }
        if ((r->parent = ro) == NULL) {         /* primary ray */
                r->rlvl = 0;
                r->rweight = rw;
                r->crtype = r->rtype = rt;
                r->rsrc = -1;
#ifdef SSKIPOPT
                r->scorr = 1.f;
#endif
                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*.99) {
                        memset(r, 0, sizeof(RAY));
                        return(-1);             /* illegal continuation */
                }
                r->rlvl = ro->rlvl;
                r->rsrc = ro->rsrc;
#ifdef SSKIPOPT
                r->scorr = ro->scorr;
#endif
                if (rt & RAYREFL) {
                        r->rlvl++;
                        if (r->rsrc >= 0)       /* malfunctioning material? */
                                r->rsrc = -1;
                        r->clipset = ro->clipset;
                        r->rmax = 0.0;
                } else {
                        r->clipset = ro->newcset;
                        r->rmax = (ro->rmax > FTINY)*(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);
                                                /* ambient in photon map? */
        if (ro != NULL && ro->crtype & AMBIENT) {
                if (causticPhotonMapping)
                        return(-1);
                if (photonMapping && rt != TRANS)
                        return(-1);
        }
        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 */
                scalescolor(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->rxt = r->rmt = r->rot = FHUGE;
        VCOPY(r->rop, r->rorg);
        r->ron[0] = -r->rdir[0]; r->ron[1] = -r->rdir[1]; r->ron[2] = -r->rdir[2];
        r->rod = 1.0;
        r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
        r->rflips = 0;
        r->uv[0] = r->uv[1] = 0.0;
        setscolor(r->pcol, 1.0, 1.0, 1.0);
        scolorblack(r->mcol);
        scolorblack(r->rcol);
}


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;

        rayorigin(&tr, TRANS, r, NULL);         /* always continue */
        VCOPY(tr.rdir, r->rdir);
        rayvalue(&tr);
        copyscolor(r->mcol, tr.mcol);
        copyscolor(r->rcol, tr.rcol);
        r->rmt = r->rot + tr.rmt;
        r->rxt = r->rot + tr.rxt;
}


int
raytirrad(                      /* irradiance hack */
        OBJREC  *m,
        RAY     *r
)
{
        if (ofun[m->otype].flags & (T_M|T_X) && m->otype != MAT_CLIP) {
                if (istransp(m->otype) || isBSDFproxy(m)) {
                        raytrans(r);
                        return(1);
                }
                if (!islight(m->otype)) {
                        setscolor(r->pcol, 1.0, 1.0, 1.0);
                        return((*ofun[Lamb.otype].funp)(&Lamb, r));
                }
        }
        return(0);              /* not a qualifying surface */
}


int
rayshade(               /* shade ray r with material mod */
        RAY  *r,
        int  mod
)
{
        int     tst_irrad = do_irrad && !(r->crtype & ~(PRIMARY|TRANS));
        OBJREC  *m;

        r->rxt = r->rot;                /* preset 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 (tst_irrad && raytirrad(m, r))
                        return(1);

                if ((*ofun[m->otype].funp)(m, r))
                        return(1);      /* materials call raytexture() */
        }
        return(0);                      /* no material! */
}


void
rayparticipate(                 /* compute ray medium participation */
        RAY  *r
)
{
        SCOLOR  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);
        }
        setscolor(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));
        smultscolor(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) {
                setscolor(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)));
                saddscolor(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;
        double  mfore, mback;
        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;
                scalescolor(fr.rcoef, coef);
                foremat = rayshade(&fr, fore);
        }
                                        /* background */
        br = *r;
        if (coef < 1.0-FTINY) {
                br.rweight *= 1.0-coef;
                scalescolor(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 */
        scalescolor(fr.pcol, coef);
        scalescolor(br.pcol, 1.0-coef);
        copyscolor(r->pcol, fr.pcol);
        saddscolor(r->pcol, br.pcol);
                                        /* return value tells if material */
        if (!foremat & !backmat)
                return(0);
                                        /* mix returned ray values */
        scalescolor(fr.rcol, coef);
        scalescolor(br.rcol, 1.0-coef);
        copyscolor(r->rcol, fr.rcol);
        saddscolor(r->rcol, br.rcol);
        scalescolor(fr.mcol, coef);
        scalescolor(br.mcol, 1.0-coef);
        copyscolor(r->mcol, fr.mcol);
        saddscolor(r->mcol, br.mcol);
        mfore = pbright(fr.mcol); mback = pbright(br.mcol);
        r->rmt = mfore > mback ? fr.rmt : br.rmt;
        r->rxt = pbright(fr.rcol)-mfore > pbright(br.rcol)-mback ?
                        fr.rxt : br.rxt;
        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 */
        SCOLOR  rc,
        const RAY  *r,
        int  flags
)
{
        static int      warnedPM = 0;

        setscolor(rc, 1., 1., 1.);

        while (r != NULL && r->crtype&flags) {
                smultscolor(rc, r->rcoef);
                                        /* check for participating medium */
                if (!warnedPM && (bright(r->cext) > FTINY) |
                                (bright(r->albedo) > FTINY)) {
                        error(WARNING,
        "ray contribution calculation does not support participating media");
                        warnedPM++;
                }
                r = r->parent;
        }
}


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];
        r->rflips++;
}


int
rayreject(              /* check if candidate hit is worse than current */
        OBJREC *o,
        RAY *r,
        double t,
        double rod
)
{
        OBJREC  *mnew, *mray;

        if ((t <= FTINY) | (t > r->rot + FTINY))
                return(1);
        if (t < r->rot - FTINY)         /* is new hit significantly closer? */
                return(0);
                                        /* coincident point, so decide... */
        if (o == r->ro)
                return(1);              /* shouldn't happen */
        if (r->ro == NULL)
                return(0);              /* ditto */
        mnew = findmaterial(o);
        mray = findmaterial(r->ro);     /* check material transparencies */
        if (mnew == NULL) {
                if (mray != NULL)
                        return(1);      /* old has material, new does not */
        } else if (mray == NULL) {
                return(0);              /* new has material, old does not */
        } else if (istransp(mnew->otype)) {
                if (!istransp(mray->otype))
                        return(1);      /* new is transparent, old is not */
        } else if (istransp(mray->otype)) {
                return(0);              /* old is transparent, new is not */
        }
        if (rod <= 0) {                 /* check which side we hit */
                if (r->rod > 0)
                        return(1);      /* old hit front, new did not */
        } else if (r->rod <= 0) {
                return(0);              /* new hit front, old did not */
        }
                        /* earlier modifier definition wins tie */
        return (r->ro->omod >= o->omod);
}

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:	2.90
Committed:	Fri Nov 15 20:47:42 2024 UTC (5 months, 2 weeks ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.89:	+11 -4 lines
Log Message:	feat(rpict): Experimental source skipping option with -DSSKIPOPT compile flag