src/rt/ambient.c

/* Copyright (c) 1995 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 *  ambient.c - routines dealing with ambient (inter-reflected) component.
 */

#include  "ray.h"

#include  "octree.h"

#include  "otypes.h"

#include  "ambient.h"

#include  "random.h"

#define  OCTSCALE       0.5     /* ceil((valid rad.)/(cube size)) */

typedef struct ambtree {
        AMBVAL  *alist;         /* ambient value list */
        struct ambtree  *kid;   /* 8 child nodes */
}  AMBTREE;                     /* ambient octree */

extern CUBE  thescene;          /* contains space boundaries */

extern char  *shm_boundary;     /* memory sharing boundary */

#define  MAXASET        511     /* maximum number of elements in ambient set */
OBJECT  ambset[MAXASET+1]={0};  /* ambient include/exclude set */

double  maxarad;                /* maximum ambient radius */
double  minarad;                /* minimum ambient radius */

static AMBTREE  atrunk;         /* our ambient trunk node */

static FILE  *ambfp = NULL;     /* ambient file pointer */
static int  nunflshed = 0;      /* number of unflushed ambient values */

#ifndef SORT_THRESH
#ifdef BIGMEM
#define SORT_THRESH     ((9L<<20)/sizeof(AMBVAL))
#else
#define SORT_THRESH     ((3L<<20)/sizeof(AMBVAL))
#endif
#endif
#ifndef SORT_INTVL
#define SORT_INTVL      (SORT_THRESH*8)
#endif

static unsigned long  ambclock = 0;     /* ambient access clock */
static unsigned int  nambvals = 0;      /* number of stored ambient values */
static unsigned long  lastsort = 0;     /* time of last value sort */
static long  sortintvl = SORT_INTVL;    /* time until next sort */

#define MAXACLOCK       (1L<<30)        /* clock turnover value */
        /*
         * Track access times unless we are sharing ambient values
         * through memory on a multiprocessor, when we want to avoid
         * claiming our own memory (copy on write).
         */
#define tracktime       (shm_boundary == NULL || ambfp == NULL)
#define checksort()     if (ambclock > lastsort+sortintvl && \
                        nambvals > SORT_THRESH) sortambvals(0)

#define  AMBFLUSH       (BUFSIZ/AMBVALSIZ)

#define  newambval()    (AMBVAL *)bmalloc(sizeof(AMBVAL))

extern long  ftell(), lseek();
static int  initambfile(), avsave(), avinsert(), sortambvals();
static AMBVAL  *avstore();
#ifdef  F_SETLKW
static  aflock();
#endif


setambres(ar)                           /* set ambient resolution */
int  ar;
{
        ambres = ar < 0 ? 0 : ar;               /* may be done already */
                                                /* set min & max radii */
        if (ar <= 0) {
                minarad = 0;
                maxarad = thescene.cusize / 2.0;
        } else {
                minarad = thescene.cusize / ar;
                maxarad = 16 * minarad;                 /* heuristic */
                if (maxarad > thescene.cusize / 2.0)
                        maxarad = thescene.cusize / 2.0;
        }
        if (minarad <= FTINY)
                minarad = 10*FTINY;
        if (maxarad <= minarad)
                maxarad = 64 * minarad;
}


setambacc(newa)                         /* set ambient accuracy */
double  newa;
{
        static double  oldambacc = -1.0;

        ambacc = newa < 0.0 ? 0.0 : newa;       /* may be done already */
        if (oldambacc < -FTINY)
                oldambacc = ambacc;     /* do nothing first call */
        if (fabs(newa - oldambacc) < 0.01)
                return;                 /* insignificant -- don't bother */
        if (ambacc <= FTINY)
                return;                 /* cannot build new tree */
                                        /* else need to rebuild tree */
        sortambvals(1);
        oldambacc = ambacc;             /* remeber setting for next call */
}


setambient(afile)                       /* initialize calculation */
char  *afile;
{
        long  headlen;
        AMBVAL  amb;
                                                /* init ambient limits */
        setambres(ambres);
        setambacc(ambacc);
        if (afile == NULL)
                return;
        if (ambacc <= FTINY) {
                sprintf(errmsg, "zero ambient accuracy so \"%s\" not opened",
                                afile);
                error(WARNING, errmsg);
                return;
        }
                                                /* open ambient file */
        if ((ambfp = fopen(afile, "r+")) != NULL) {
                initambfile(0);
                headlen = ftell(ambfp);
                while (readambval(&amb, ambfp))
                        avinsert(avstore(&amb));
                                                /* align */
                fseek(ambfp, -((ftell(ambfp)-headlen)%AMBVALSIZ), 1);
        } else if ((ambfp = fopen(afile, "w+")) != NULL)
                initambfile(1);
        else {
                sprintf(errmsg, "cannot open ambient file \"%s\"", afile);
                error(SYSTEM, errmsg);
        }
        nunflshed++;    /* lie */
        ambsync();
}


ambnotify(obj)                  /* record new modifier */
OBJECT  obj;
{
        static int  hitlimit = 0;
        register OBJREC  *o = objptr(obj);
        register char  **amblp;

        if (hitlimit || !ismodifier(o->otype))
                return;
        for (amblp = amblist; *amblp != NULL; amblp++)
                if (!strcmp(o->oname, *amblp)) {
                        if (ambset[0] >= MAXASET) {
                                error(WARNING, "too many modifiers in ambient list");
                                hitlimit++;
                                return;         /* should this be fatal? */
                        }
                        insertelem(ambset, obj);
                        return;
                }
}


ambient(acol, r)                /* compute ambient component for ray */
COLOR  acol;
register RAY  *r;
{
        static int  rdepth = 0;                 /* ambient recursion */
        double  d;

        if (ambdiv <= 0)                        /* no ambient calculation */
                goto dumbamb;
                                                /* check number of bounces */
        if (rdepth >= ambounce)
                goto dumbamb;
                                                /* check ambient list */
        if (ambincl != -1 && r->ro != NULL &&
                        ambincl != inset(ambset, r->ro->omod))
                goto dumbamb;

        if (ambacc <= FTINY) {                  /* no ambient storage */
                rdepth++;
                d = doambient(acol, r, r->rweight, NULL, NULL);
                rdepth--;
                if (d == 0.0)
                        goto dumbamb;
                return;
        }
                                                /* resort memory? */
        checksort();
                                                /* get ambient value */
        setcolor(acol, 0.0, 0.0, 0.0);
        d = sumambient(acol, r, rdepth,
                        &atrunk, thescene.cuorg, thescene.cusize);
        if (d > FTINY)
                scalecolor(acol, 1.0/d);
        else {
                d = makeambient(acol, r, rdepth++);
                rdepth--;
        }
        if (d > FTINY)
                return;
dumbamb:                                        /* return global value */
        copycolor(acol, ambval);
}


double
sumambient(acol, r, al, at, c0, s)      /* get interpolated ambient value */
COLOR  acol;
register RAY  *r;
int  al;
AMBTREE  *at;
FVECT  c0;
double  s;
{
        double  d, e1, e2, wt, wsum;
        COLOR  ct;
        FVECT  ck0;
        int  i;
        register int  j;
        register AMBVAL  *av;
                                        /* do this node */
        wsum = 0.0;
        for (av = at->alist; av != NULL; av = av->next) {
                if (tracktime)
                        av->latick = ambclock++;
                /*
                 *  Ambient level test.
                 */
                if (av->lvl > al)       /* list sorted, so this works */
                        break;
                if (av->weight < r->rweight-FTINY)
                        continue;
                /*
                 *  Ambient radius test.
                 */
                e1 = 0.0;
                for (j = 0; j < 3; j++) {
                        d = av->pos[j] - r->rop[j];
                        e1 += d * d;
                }
                e1 /= av->rad * av->rad;
                if (e1 > ambacc*ambacc*1.21)
                        continue;
                /*
                 *  Normal direction test.
                 */
                e2 = (1.0 - DOT(av->dir, r->ron)) * r->rweight;
                if (e2 < 0.0) e2 = 0.0;
                if (e1 + e2 > ambacc*ambacc*1.21)
                        continue;
                /*
                 *  Ray behind test.
                 */
                d = 0.0;
                for (j = 0; j < 3; j++)
                        d += (r->rop[j] - av->pos[j]) *
                                        (av->dir[j] + r->ron[j]);
                if (d*0.5 < -minarad*ambacc-.001)
                        continue;
                /*
                 *  Jittering final test reduces image artifacts.
                 */
                wt = sqrt(e1) + sqrt(e2);
                wt *= .9 + .2*urand(9015+samplendx);
                if (wt > ambacc)
                        continue;
                if (wt <= 1e-3)
                        wt = 1e3;
                else
                        wt = 1.0 / wt;
                wsum += wt;
                extambient(ct, av, r->rop, r->ron);
                scalecolor(ct, wt);
                addcolor(acol, ct);
        }
        if (at->kid == NULL)
                return(wsum);
                                        /* do children */
        s *= 0.5;
        for (i = 0; i < 8; i++) {
                for (j = 0; j < 3; j++) {
                        ck0[j] = c0[j];
                        if (1<<j & i)
                                ck0[j] += s;
                        if (r->rop[j] < ck0[j] - OCTSCALE*s)
                                break;
                        if (r->rop[j] > ck0[j] + (1.0+OCTSCALE)*s)
                                break;
                }
                if (j == 3)
                        wsum += sumambient(acol, r, al, at->kid+i, ck0, s);
        }
        return(wsum);
}


double
makeambient(acol, r, al)        /* make a new ambient value */
COLOR  acol;
register RAY  *r;
int  al;
{
        AMBVAL  amb;
        FVECT   gp, gd;
                                                /* compute weight */
        amb.weight = pow(AVGREFL, (double)al);
        if (r->rweight < 0.2*amb.weight)        /* heuristic */
                amb.weight = r->rweight;
                                                /* compute ambient */
        amb.rad = doambient(acol, r, amb.weight, gp, gd);
        if (amb.rad == 0.0)
                return(0.0);
                                                /* store it */
        VCOPY(amb.pos, r->rop);
        VCOPY(amb.dir, r->ron);
        amb.lvl = al;
        copycolor(amb.val, acol);
        VCOPY(amb.gpos, gp);
        VCOPY(amb.gdir, gd);
                                                /* insert into tree */
        avsave(&amb);                           /* and save to file */
        return(amb.rad);
}


extambient(cr, ap, pv, nv)              /* extrapolate value at pv, nv */
COLOR  cr;
register AMBVAL  *ap;
FVECT  pv, nv;
{
        FVECT  v1, v2;
        register int  i;
        double  d;

        d = 1.0;                        /* zeroeth order */
                                        /* gradient due to translation */
        for (i = 0; i < 3; i++)
                d += ap->gpos[i]*(pv[i]-ap->pos[i]);
                                        /* gradient due to rotation */
        VCOPY(v1, ap->dir);
        fcross(v2, v1, nv);
        d += DOT(ap->gdir, v2);
        if (d <= 0.0) {
                setcolor(cr, 0.0, 0.0, 0.0);
                return;
        }
        copycolor(cr, ap->val);
        scalecolor(cr, d);
}


static
initambfile(creat)              /* initialize ambient file */
int  creat;
{
        extern char  *progname, *octname, VersionID[];

#ifdef  F_SETLKW
        aflock(creat ? F_WRLCK : F_RDLCK);
#endif
#ifdef MSDOS
        setmode(fileno(ambfp), O_BINARY);
#endif
        setbuf(ambfp, bmalloc(BUFSIZ+8));
        if (creat) {                    /* new file */
                newheader("RADIANCE", ambfp);
                fprintf(ambfp, "%s -av %g %g %g -ab %d -aa %g ",
                                progname, colval(ambval,RED),
                                colval(ambval,GRN), colval(ambval,BLU),
                                ambounce, ambacc);
                fprintf(ambfp, "-ad %d -as %d -ar %d %s\n",
                                ambdiv, ambssamp, ambres,
                                octname==NULL ? "" : octname);
                fprintf(ambfp, "SOFTWARE= %s\n", VersionID);
                fputformat(AMBFMT, ambfp);
                putc('\n', ambfp);
                putambmagic(ambfp);
        } else if (checkheader(ambfp, AMBFMT, NULL) < 0 || !hasambmagic(ambfp))
                error(USER, "bad ambient file");
}


static
avsave(av)                              /* insert and save an ambient value */
AMBVAL  *av;
{
        avinsert(avstore(av));
        if (ambfp == NULL)
                return;
        if (writambval(av, ambfp) < 0)
                goto writerr;
        if (++nunflshed >= AMBFLUSH)
                if (ambsync() == EOF)
                        goto writerr;
        return;
writerr:
        error(SYSTEM, "error writing ambient file");
}


static AMBVAL *
avstore(aval)                           /* allocate memory and store aval */
register AMBVAL  *aval;
{
        register AMBVAL  *av;

        if ((av = newambval()) == NULL)
                error(SYSTEM, "out of memory in avstore");
        copystruct(av, aval);
        av->latick = ambclock;
        av->next = NULL;
        nambvals++;
        return(av);
}


#define ATALLOCSZ       512             /* #/8 trees to allocate at once */

static AMBTREE  *atfreelist = NULL;     /* free ambient tree structures */


static
AMBTREE *
newambtree()                            /* allocate 8 ambient tree structs */
{
        register AMBTREE  *atp, *upperlim;

        if (atfreelist == NULL) {       /* get more nodes */
                atfreelist = (AMBTREE *)bmalloc(ATALLOCSZ*8*sizeof(AMBTREE));
                if (atfreelist == NULL)
                        return(NULL);
                                        /* link new free list */
                upperlim = atfreelist + 8*(ATALLOCSZ-1);
                for (atp = atfreelist; atp < upperlim; atp += 8)
                        atp->kid = atp + 8;
                atp->kid = NULL;
        }
        atp = atfreelist;
        atfreelist = atp->kid;
        bzero((char *)atp, 8*sizeof(AMBTREE));
        return(atp);
}


static
freeambtree(atp)                        /* free 8 ambient tree structs */
AMBTREE  *atp;
{
        atp->kid = atfreelist;
        atfreelist = atp;
}


static
avinsert(av)                            /* insert ambient value in our tree */
register AMBVAL  *av;
{
        register AMBTREE  *at;
        register AMBVAL  *ap;
        AMBVAL  avh;
        FVECT  ck0;
        double  s;
        int  branch;
        register int  i;

        if (av->rad <= FTINY)
                error(CONSISTENCY, "zero ambient radius in avinsert");
        at = &atrunk;
        VCOPY(ck0, thescene.cuorg);
        s = thescene.cusize;
        while (s*(OCTSCALE/2) > av->rad*ambacc) {
                if (at->kid == NULL)
                        if ((at->kid = newambtree()) == NULL)
                                error(SYSTEM, "out of memory in avinsert");
                s *= 0.5;
                branch = 0;
                for (i = 0; i < 3; i++)
                        if (av->pos[i] > ck0[i] + s) {
                                ck0[i] += s;
                                branch |= 1 << i;
                        }
                at = at->kid + branch;
        }
        avh.next = at->alist;           /* order by increasing level */
        for (ap = &avh; ap->next != NULL; ap = ap->next)
                if (ap->next->lvl >= av->lvl)
                        break;
        av->next = ap->next;
        ap->next = av;
        at->alist = avh.next;
}


static
unloadatree(at, f)                      /* unload an ambient value tree */
register AMBTREE  *at;
int     (*f)();
{
        register AMBVAL  *av;
        register int  i;
                                        /* transfer values at this node */
        for (av = at->alist; av != NULL; av = at->alist) {
                at->alist = av->next;
                (*f)(av);
        }
        if (at->kid == NULL)
                return;
        for (i = 0; i < 8; i++)         /* transfer and free children */
                unloadatree(at->kid+i, f);
        freeambtree(at->kid);
        at->kid = NULL;
}


static AMBVAL   **avlist1, **avlist2;   /* ambient value lists for sorting */
static int      i_avlist;               /* index for lists */


static
av2list(av)
AMBVAL  *av;
{
#ifdef DEBUG
        if (i_avlist >= nambvals)
                error(CONSISTENCY, "too many ambient values in av2list1");
#endif
        avlist1[i_avlist] = avlist2[i_avlist] = av;
        i_avlist++;
}


static int
alatcmp(avp1, avp2)                     /* compare ambient values for MRA */
AMBVAL  **avp1, **avp2;
{
        return((**avp2).latick - (**avp1).latick);
}


static int
aposcmp(avp1, avp2)                     /* compare ambient value positions */
AMBVAL  **avp1, **avp2;
{
        return(*avp1 - *avp2);
}


#ifdef DEBUG
static int
avlmemi(avaddr)                         /* find list position from address */
AMBVAL  *avaddr;
{
        register AMBVAL  **avlpp;

        avlpp = (AMBVAL **)bsearch((char *)&avaddr, (char *)avlist2,
                        nambvals, sizeof(AMBVAL *), aposcmp);
        if (avlpp == NULL)
                error(CONSISTENCY, "address not found in avlmemi");
        return(avlpp - avlist2);
}
#else
#define avlmemi(avaddr) ((AMBVAL **)bsearch((char *)&avaddr,(char *)avlist2, \
                                nambvals,sizeof(AMBVAL *),aposcmp) - avlist2)
#endif


static
sortambvals(always)                     /* resort ambient values */
int     always;
{
        AMBTREE  oldatrunk;
        AMBVAL  tav, *tap, *pnext;
        register int    i, j;
        /*
         * The idea here is to minimize memory thrashing
         * in VM systems by improving reference locality.
         * We do this by periodically sorting our stored ambient
         * values in memory in order of most recently to least
         * recently accessed.  This ordering was chosen so that new
         * ambient values (which tend to be less important) go into
         * higher memory with the infrequently accessed values.
         *      Since we expect our values to need sorting less
         * frequently as the process continues, we double our
         * waiting interval after each call.
         *      This routine is also called by setambacc() with
         * the "always" parameter set to 1 so that the ambient
         * tree will be rebuilt with the new accuracy parameter.
         */
        if (tracktime) {                /* allocate pointer arrays to sort */
                avlist1 = (AMBVAL **)malloc(nambvals*sizeof(AMBVAL *));
                avlist2 = (AMBVAL **)malloc(nambvals*sizeof(AMBVAL *));
        } else
                avlist1 = avlist2 = NULL;
        if (avlist2 == NULL) {          /* no time tracking -- rebuild tree? */
                if (avlist1 != NULL)
                        free((char *)avlist1);
                if (always) {           /* rebuild without sorting */
                        copystruct(&oldatrunk, &atrunk);
                        atrunk.alist = NULL;
                        atrunk.kid = NULL;
                        unloadatree(&oldatrunk, avinsert);
                }
        } else {                        /* sort memory by last access time */
                /*
                 * Sorting memory is tricky because it isn't contiguous.
                 * We have to sort an array of pointers by MRA and also
                 * by memory position.  We then copy values in "loops"
                 * to minimize memory hits.  Nevertheless, we will visit
                 * everyone at least twice, and this is an expensive process
                 * when we're thrashing, which is when we need to do it.
                 */
#ifdef DEBUG
                sprintf(errmsg, "sorting %u ambient values...", nambvals);
                eputs(errmsg);
#endif
                i_avlist = 0;
                unloadatree(&atrunk, av2list);  /* empty current tree */
#ifdef DEBUG
                if (i_avlist < nambvals)
                        error(CONSISTENCY, "missing ambient values in sortambvals");
#endif
                qsort((char *)avlist1, nambvals, sizeof(AMBVAL *), alatcmp);
                qsort((char *)avlist2, nambvals, sizeof(AMBVAL *), aposcmp);
                for (i = 0; i < nambvals; i++) {
                        if (avlist1[i] == NULL)
                                continue;
                        tap = avlist2[i];
                        copystruct(&tav, tap);
                        for (j = i; (pnext = avlist1[j]) != tap;
                                        j = avlmemi(pnext)) {
                                copystruct(avlist2[j], pnext);
                                avinsert(avlist2[j]);
                                avlist1[j] = NULL;
                        }
                        copystruct(avlist2[j], &tav);
                        avinsert(avlist2[j]);
                        avlist1[j] = NULL;
                }
                free((char *)avlist1);
                free((char *)avlist2);
                if (sortintvl < SORT_INTVL<<6)
                        sortintvl <<= 1;        /* wait twice as long next */
#ifdef DEBUG
                eputs("done\n");
#endif
        }
        if (ambclock >= MAXACLOCK)
                ambclock = MAXACLOCK/2;
        lastsort = ambclock;
}


#ifdef  F_SETLKW

static
aflock(typ)                     /* lock/unlock ambient file */
int  typ;
{
        static struct flock  fls;       /* static so initialized to zeroes */

        fls.l_type = typ;
        if (fcntl(fileno(ambfp), F_SETLKW, &fls) < 0)
                error(SYSTEM, "cannot (un)lock ambient file");
}


int
ambsync()                       /* synchronize ambient file */
{
        static FILE  *ambinp = NULL;
        static long  lastpos = -1;
        long  flen;
        AMBVAL  avs;
        register int  n;

        if (nunflshed == 0)
                return(0);
        if (lastpos < 0)        /* initializing (locked in initambfile) */
                goto syncend;
                                /* gain exclusive access */
        aflock(F_WRLCK);
                                /* see if file has grown */
        if ((flen = lseek(fileno(ambfp), 0L, 2)) < 0)
                goto seekerr;
        if (n = flen - lastpos) {               /* file has grown */
                if (ambinp == NULL) {           /* use duplicate filedes */
                        ambinp = fdopen(dup(fileno(ambfp)), "r");
                        if (ambinp == NULL)
                                error(SYSTEM, "fdopen failed in ambsync");
                }
                if (fseek(ambinp, lastpos, 0) < 0)
                        goto seekerr;
                while (n >= AMBVALSIZ) {        /* load contributed values */
                        readambval(&avs, ambinp);
                        avinsert(avstore(&avs));
                        n -= AMBVALSIZ;
                }
                /*** seek always as safety measure
                if (n) ***/                     /* alignment */
                        if (lseek(fileno(ambfp), flen-n, 0) < 0)
                                goto seekerr;
        }
#ifdef  DEBUG
        if (ambfp->_ptr - ambfp->_base != nunflshed*AMBVALSIZ) {
                sprintf(errmsg, "ambient file buffer at %d rather than %d",
                                ambfp->_ptr - ambfp->_base,
                                nunflshed*AMBVALSIZ);
                error(CONSISTENCY, errmsg);
        }
#endif
syncend:
        n = fflush(ambfp);                      /* calls write() at last */
        if ((lastpos = lseek(fileno(ambfp), 0L, 1)) < 0)
                goto seekerr;
        aflock(F_UNLCK);                        /* release file */
        nunflshed = 0;
        return(n);
seekerr:
        error(SYSTEM, "seek failed in ambsync");
}

#else

int
ambsync()                       /* flush ambient file */
{
        if (nunflshed == 0)
                return(0);
        nunflshed = 0;
        return(fflush(ambfp));
}

#endif
Revision:	2.27
Committed:	Sat Apr 29 10:51:28 1995 UTC (30 years, 6 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.26:	+63 -29 lines
Log Message:	minor improvements
#	User	Rev	Content
1	greg	2.27	/* Copyright (c) 1995 Regents of the University of California */
2	greg	1.1
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* ambient.c - routines dealing with ambient (inter-reflected) component.
9			*/
10
11			#include "ray.h"
12
13			#include "octree.h"
14
15	greg	1.8	#include "otypes.h"
16
17	greg	1.14	#include "ambient.h"
18
19	greg	1.1	#include "random.h"
20
21	greg	2.12	#define OCTSCALE 0.5 /* ceil((valid rad.)/(cube size)) */
22	greg	1.1
23	greg	1.14	typedef struct ambtree {
24	greg	2.12	AMBVAL alist; / ambient value list */
25			struct ambtree kid; / 8 child nodes */
26	greg	1.14	} AMBTREE; /* ambient octree */
27
28	greg	1.1	extern CUBE thescene; /* contains space boundaries */
29
30	greg	2.27	extern char shm_boundary; / memory sharing boundary */
31	greg	2.26
32	greg	2.12	#define MAXASET 511 /* maximum number of elements in ambient set */
33			OBJECT ambset[MAXASET+1]={0}; /* ambient include/exclude set */
34	greg	1.1
35	greg	2.12	double maxarad; /* maximum ambient radius */
36			double minarad; /* minimum ambient radius */
37	greg	1.1
38	greg	2.12	static AMBTREE atrunk; /* our ambient trunk node */
39	greg	1.1
40			static FILE ambfp = NULL; / ambient file pointer */
41	greg	2.16	static int nunflshed = 0; /* number of unflushed ambient values */
42	greg	1.1
43	greg	2.26	#ifndef SORT_THRESH
44			#ifdef BIGMEM
45	greg	2.27	#define SORT_THRESH ((9L<<20)/sizeof(AMBVAL))
46	greg	2.26	#else
47	greg	2.27	#define SORT_THRESH ((3L<<20)/sizeof(AMBVAL))
48	greg	2.26	#endif
49			#endif
50			#ifndef SORT_INTVL
51	greg	2.27	#define SORT_INTVL (SORT_THRESH*8)
52	greg	2.26	#endif
53
54	greg	2.27	static unsigned long ambclock = 0; /* ambient access clock */
55			static unsigned int nambvals = 0; /* number of stored ambient values */
56			static unsigned long lastsort = 0; /* time of last value sort */
57	greg	2.26	static long sortintvl = SORT_INTVL; /* time until next sort */
58
59			#define MAXACLOCK (1L<<30) /* clock turnover value */
60	greg	2.27	/*
61			* Track access times unless we are sharing ambient values
62			* through memory on a multiprocessor, when we want to avoid
63			* claiming our own memory (copy on write).
64			*/
65	greg	2.26	#define tracktime (shm_boundary == NULL \|\| ambfp == NULL)
66	greg	2.27	#define checksort() if (ambclock > lastsort+sortintvl && \
67			nambvals > SORT_THRESH) sortambvals(0)
68	greg	2.26
69	greg	2.12	#define AMBFLUSH (BUFSIZ/AMBVALSIZ)
70	greg	2.6
71	greg	2.12	#define newambval() (AMBVAL *)bmalloc(sizeof(AMBVAL))
72	greg	1.1
73	greg	2.7	extern long ftell(), lseek();
74	greg	2.26	static int initambfile(), avsave(), avinsert(), sortambvals();
75	greg	2.20	static AMBVAL *avstore();
76	greg	2.19	#ifdef F_SETLKW
77			static aflock();
78			#endif
79	greg	1.1
80	greg	2.7
81	greg	2.3	setambres(ar) /* set ambient resolution */
82			int ar;
83			{
84	greg	2.21	ambres = ar < 0 ? 0 : ar; /* may be done already */
85	greg	2.3	/* set min & max radii */
86			if (ar <= 0) {
87	greg	2.25	minarad = 0;
88	greg	2.3	maxarad = thescene.cusize / 2.0;
89			} else {
90			minarad = thescene.cusize / ar;
91	greg	2.25	maxarad = 16 * minarad; /* heuristic */
92	greg	2.3	if (maxarad > thescene.cusize / 2.0)
93			maxarad = thescene.cusize / 2.0;
94			}
95	greg	2.25	if (minarad <= FTINY)
96			minarad = 10*FTINY;
97			if (maxarad <= minarad)
98			maxarad = 64 * minarad;
99	greg	2.3	}
100
101
102	greg	2.21	setambacc(newa) /* set ambient accuracy */
103	greg	2.20	double newa;
104			{
105	greg	2.21	static double oldambacc = -1.0;
106	greg	2.20
107	greg	2.21	ambacc = newa < 0.0 ? 0.0 : newa; /* may be done already */
108			if (oldambacc < -FTINY)
109			oldambacc = ambacc; /* do nothing first call */
110			if (fabs(newa - oldambacc) < 0.01)
111	greg	2.20	return; /* insignificant -- don't bother */
112			if (ambacc <= FTINY)
113			return; /* cannot build new tree */
114			/* else need to rebuild tree */
115	greg	2.26	sortambvals(1);
116	greg	2.21	oldambacc = ambacc; /* remeber setting for next call */
117	greg	2.20	}
118
119
120	greg	1.1	setambient(afile) /* initialize calculation */
121			char *afile;
122			{
123	greg	2.9	long headlen;
124	greg	2.12	AMBVAL amb;
125	greg	2.3	/* init ambient limits */
126			setambres(ambres);
127	greg	2.21	setambacc(ambacc);
128	greg	2.19	if (afile == NULL)
129			return;
130	greg	2.20	if (ambacc <= FTINY) {
131	greg	2.21	sprintf(errmsg, "zero ambient accuracy so \"%s\" not opened",
132	greg	2.20	afile);
133			error(WARNING, errmsg);
134			return;
135			}
136	greg	2.3	/* open ambient file */
137	greg	2.19	if ((ambfp = fopen(afile, "r+")) != NULL) {
138			initambfile(0);
139			headlen = ftell(ambfp);
140			while (readambval(&amb, ambfp))
141	greg	2.21	avinsert(avstore(&amb));
142	greg	2.19	/* align */
143			fseek(ambfp, -((ftell(ambfp)-headlen)%AMBVALSIZ), 1);
144			} else if ((ambfp = fopen(afile, "w+")) != NULL)
145			initambfile(1);
146			else {
147			sprintf(errmsg, "cannot open ambient file \"%s\"", afile);
148			error(SYSTEM, errmsg);
149	greg	2.16	}
150	greg	2.19	nunflshed++; /* lie */
151			ambsync();
152	greg	1.8	}
153
154
155			ambnotify(obj) /* record new modifier */
156	greg	2.12	OBJECT obj;
157	greg	1.8	{
158	greg	1.11	static int hitlimit = 0;
159	greg	2.12	register OBJREC *o = objptr(obj);
160	greg	1.8	register char **amblp;
161
162	greg	1.11	if (hitlimit \|\| !ismodifier(o->otype))
163	greg	1.8	return;
164			for (amblp = amblist; *amblp != NULL; amblp++)
165			if (!strcmp(o->oname, *amblp)) {
166	greg	1.11	if (ambset[0] >= MAXASET) {
167			error(WARNING, "too many modifiers in ambient list");
168			hitlimit++;
169			return; /* should this be fatal? */
170			}
171	greg	1.8	insertelem(ambset, obj);
172			return;
173	greg	1.1	}
174			}
175
176
177			ambient(acol, r) /* compute ambient component for ray */
178			COLOR acol;
179			register RAY *r;
180			{
181			static int rdepth = 0; /* ambient recursion */
182	greg	2.12	double d;
183	greg	1.1
184			if (ambdiv <= 0) /* no ambient calculation */
185			goto dumbamb;
186			/* check number of bounces */
187	greg	1.16	if (rdepth >= ambounce)
188	greg	1.1	goto dumbamb;
189			/* check ambient list */
190			if (ambincl != -1 && r->ro != NULL &&
191			ambincl != inset(ambset, r->ro->omod))
192			goto dumbamb;
193
194			if (ambacc <= FTINY) { /* no ambient storage */
195	greg	1.16	rdepth++;
196			d = doambient(acol, r, r->rweight, NULL, NULL);
197			rdepth--;
198			if (d == 0.0)
199	greg	1.1	goto dumbamb;
200	greg	1.16	return;
201	greg	1.1	}
202	greg	2.27	/* resort memory? */
203			checksort();
204	greg	1.1	/* get ambient value */
205			setcolor(acol, 0.0, 0.0, 0.0);
206	greg	1.16	d = sumambient(acol, r, rdepth,
207			&atrunk, thescene.cuorg, thescene.cusize);
208			if (d > FTINY)
209			scalecolor(acol, 1.0/d);
210			else {
211			d = makeambient(acol, r, rdepth++);
212			rdepth--;
213			}
214			if (d > FTINY)
215			return;
216	greg	1.1	dumbamb: /* return global value */
217			copycolor(acol, ambval);
218			}
219
220
221			double
222	greg	1.16	sumambient(acol, r, al, at, c0, s) /* get interpolated ambient value */
223	greg	1.1	COLOR acol;
224			register RAY *r;
225	greg	1.16	int al;
226	greg	2.12	AMBTREE *at;
227	greg	1.1	FVECT c0;
228	greg	2.12	double s;
229	greg	1.1	{
230	greg	2.12	double d, e1, e2, wt, wsum;
231	greg	1.1	COLOR ct;
232			FVECT ck0;
233			int i;
234			register int j;
235	greg	2.12	register AMBVAL *av;
236	greg	1.7	/* do this node */
237	greg	1.1	wsum = 0.0;
238			for (av = at->alist; av != NULL; av = av->next) {
239	greg	2.26	if (tracktime)
240			av->latick = ambclock++;
241	greg	1.1	/*
242	greg	1.16	* Ambient level test.
243	greg	1.1	*/
244	greg	2.23	if (av->lvl > al) /* list sorted, so this works */
245			break;
246			if (av->weight < r->rweight-FTINY)
247	greg	1.1	continue;
248			/*
249			* Ambient radius test.
250			*/
251			e1 = 0.0;
252			for (j = 0; j < 3; j++) {
253			d = av->pos[j] - r->rop[j];
254			e1 += d * d;
255			}
256			e1 /= av->rad * av->rad;
257			if (e1 > ambaccambacc1.21)
258			continue;
259			/*
260			* Normal direction test.
261			*/
262			e2 = (1.0 - DOT(av->dir, r->ron)) * r->rweight;
263			if (e2 < 0.0) e2 = 0.0;
264			if (e1 + e2 > ambaccambacc1.21)
265			continue;
266			/*
267			* Ray behind test.
268			*/
269			d = 0.0;
270			for (j = 0; j < 3; j++)
271			d += (r->rop[j] - av->pos[j]) *
272			(av->dir[j] + r->ron[j]);
273	greg	1.18	if (d0.5 < -minaradambacc-.001)
274	greg	1.1	continue;
275			/*
276			* Jittering final test reduces image artifacts.
277			*/
278			wt = sqrt(e1) + sqrt(e2);
279	greg	2.2	wt = .9 + .2urand(9015+samplendx);
280	greg	1.6	if (wt > ambacc)
281	greg	1.1	continue;
282			if (wt <= 1e-3)
283			wt = 1e3;
284			else
285			wt = 1.0 / wt;
286			wsum += wt;
287	greg	1.15	extambient(ct, av, r->rop, r->ron);
288	greg	1.1	scalecolor(ct, wt);
289			addcolor(acol, ct);
290	greg	1.7	}
291			if (at->kid == NULL)
292			return(wsum);
293			/* do children */
294			s *= 0.5;
295			for (i = 0; i < 8; i++) {
296			for (j = 0; j < 3; j++) {
297			ck0[j] = c0[j];
298			if (1<<j & i)
299			ck0[j] += s;
300			if (r->rop[j] < ck0[j] - OCTSCALE*s)
301			break;
302			if (r->rop[j] > ck0[j] + (1.0+OCTSCALE)*s)
303			break;
304			}
305			if (j == 3)
306	greg	1.16	wsum += sumambient(acol, r, al, at->kid+i, ck0, s);
307	greg	1.1	}
308			return(wsum);
309			}
310
311
312			double
313	greg	1.16	makeambient(acol, r, al) /* make a new ambient value */
314	greg	1.1	COLOR acol;
315			register RAY *r;
316	greg	1.16	int al;
317	greg	1.1	{
318	greg	2.12	AMBVAL amb;
319	greg	1.14	FVECT gp, gd;
320	greg	1.16	/* compute weight */
321			amb.weight = pow(AVGREFL, (double)al);
322	greg	1.17	if (r->rweight < 0.2amb.weight) / heuristic */
323	greg	1.16	amb.weight = r->rweight;
324			/* compute ambient */
325			amb.rad = doambient(acol, r, amb.weight, gp, gd);
326	greg	1.1	if (amb.rad == 0.0)
327			return(0.0);
328			/* store it */
329			VCOPY(amb.pos, r->rop);
330			VCOPY(amb.dir, r->ron);
331	greg	1.16	amb.lvl = al;
332	greg	1.1	copycolor(amb.val, acol);
333	greg	1.14	VCOPY(amb.gpos, gp);
334			VCOPY(amb.gdir, gd);
335	greg	1.1	/* insert into tree */
336	greg	2.7	avsave(&amb); /* and save to file */
337	greg	1.1	return(amb.rad);
338	greg	1.15	}
339
340
341			extambient(cr, ap, pv, nv) /* extrapolate value at pv, nv */
342			COLOR cr;
343	greg	2.12	register AMBVAL *ap;
344	greg	1.15	FVECT pv, nv;
345			{
346			FVECT v1, v2;
347			register int i;
348	greg	2.12	double d;
349	greg	1.15
350			d = 1.0; /* zeroeth order */
351			/* gradient due to translation */
352			for (i = 0; i < 3; i++)
353			d += ap->gpos[i]*(pv[i]-ap->pos[i]);
354			/* gradient due to rotation */
355			VCOPY(v1, ap->dir);
356			fcross(v2, v1, nv);
357			d += DOT(ap->gdir, v2);
358			if (d <= 0.0) {
359			setcolor(cr, 0.0, 0.0, 0.0);
360			return;
361			}
362			copycolor(cr, ap->val);
363			scalecolor(cr, d);
364	greg	1.1	}
365
366
367			static
368	greg	2.9	initambfile(creat) /* initialize ambient file */
369			int creat;
370			{
371			extern char progname, octname, VersionID[];
372
373	greg	2.19	#ifdef F_SETLKW
374			aflock(creat ? F_WRLCK : F_RDLCK);
375			#endif
376	greg	2.12	#ifdef MSDOS
377			setmode(fileno(ambfp), O_BINARY);
378			#endif
379	greg	2.21	setbuf(ambfp, bmalloc(BUFSIZ+8));
380	greg	2.9	if (creat) { /* new file */
381	greg	2.24	newheader("RADIANCE", ambfp);
382	greg	2.9	fprintf(ambfp, "%s -av %g %g %g -ab %d -aa %g ",
383			progname, colval(ambval,RED),
384			colval(ambval,GRN), colval(ambval,BLU),
385			ambounce, ambacc);
386			fprintf(ambfp, "-ad %d -as %d -ar %d %s\n",
387			ambdiv, ambssamp, ambres,
388			octname==NULL ? "" : octname);
389			fprintf(ambfp, "SOFTWARE= %s\n", VersionID);
390			fputformat(AMBFMT, ambfp);
391			putc('\n', ambfp);
392			putambmagic(ambfp);
393	greg	2.17	} else if (checkheader(ambfp, AMBFMT, NULL) < 0 \|\| !hasambmagic(ambfp))
394			error(USER, "bad ambient file");
395	greg	2.9	}
396
397
398			static
399	greg	2.7	avsave(av) /* insert and save an ambient value */
400	greg	2.12	AMBVAL *av;
401	greg	1.1	{
402	greg	2.21	avinsert(avstore(av));
403	greg	1.1	if (ambfp == NULL)
404			return;
405	greg	2.5	if (writambval(av, ambfp) < 0)
406	greg	1.1	goto writerr;
407	greg	2.16	if (++nunflshed >= AMBFLUSH)
408	greg	2.7	if (ambsync() == EOF)
409	greg	1.1	goto writerr;
410			return;
411			writerr:
412	greg	2.17	error(SYSTEM, "error writing ambient file");
413	greg	1.1	}
414
415
416	greg	2.20	static AMBVAL *
417			avstore(aval) /* allocate memory and store aval */
418			register AMBVAL *aval;
419			{
420			register AMBVAL *av;
421
422			if ((av = newambval()) == NULL)
423			error(SYSTEM, "out of memory in avstore");
424			copystruct(av, aval);
425	greg	2.26	av->latick = ambclock;
426			av->next = NULL;
427			nambvals++;
428	greg	2.20	return(av);
429			}
430
431
432	greg	2.26	#define ATALLOCSZ 512 /* #/8 trees to allocate at once */
433
434			static AMBTREE atfreelist = NULL; / free ambient tree structures */
435
436
437	greg	1.1	static
438	greg	2.26	AMBTREE *
439			newambtree() /* allocate 8 ambient tree structs */
440			{
441			register AMBTREE atp, upperlim;
442
443			if (atfreelist == NULL) { /* get more nodes */
444			atfreelist = (AMBTREE )bmalloc(ATALLOCSZ8*sizeof(AMBTREE));
445			if (atfreelist == NULL)
446			return(NULL);
447			/* link new free list */
448			upperlim = atfreelist + 8*(ATALLOCSZ-1);
449			for (atp = atfreelist; atp < upperlim; atp += 8)
450			atp->kid = atp + 8;
451			atp->kid = NULL;
452			}
453			atp = atfreelist;
454			atfreelist = atp->kid;
455			bzero((char )atp, 8sizeof(AMBTREE));
456			return(atp);
457			}
458
459
460			static
461			freeambtree(atp) /* free 8 ambient tree structs */
462			AMBTREE *atp;
463			{
464			atp->kid = atfreelist;
465			atfreelist = atp;
466			}
467
468
469			static
470	greg	2.21	avinsert(av) /* insert ambient value in our tree */
471	greg	2.20	register AMBVAL *av;
472	greg	1.1	{
473	greg	2.21	register AMBTREE *at;
474	greg	2.23	register AMBVAL *ap;
475			AMBVAL avh;
476	greg	1.1	FVECT ck0;
477	greg	2.21	double s;
478	greg	1.1	int branch;
479			register int i;
480
481	greg	2.20	if (av->rad <= FTINY)
482			error(CONSISTENCY, "zero ambient radius in avinsert");
483	greg	2.21	at = &atrunk;
484			VCOPY(ck0, thescene.cuorg);
485			s = thescene.cusize;
486	greg	1.1	while (s(OCTSCALE/2) > av->radambacc) {
487			if (at->kid == NULL)
488			if ((at->kid = newambtree()) == NULL)
489	greg	2.20	error(SYSTEM, "out of memory in avinsert");
490	greg	1.1	s *= 0.5;
491			branch = 0;
492			for (i = 0; i < 3; i++)
493			if (av->pos[i] > ck0[i] + s) {
494			ck0[i] += s;
495			branch \|= 1 << i;
496			}
497			at = at->kid + branch;
498			}
499	greg	2.23	avh.next = at->alist; /* order by increasing level */
500			for (ap = &avh; ap->next != NULL; ap = ap->next)
501			if (ap->next->lvl >= av->lvl)
502			break;
503			av->next = ap->next;
504			ap->next = av;
505			at->alist = avh.next;
506	greg	2.7	}
507
508
509	greg	2.20	static
510	greg	2.26	unloadatree(at, f) /* unload an ambient value tree */
511	greg	2.20	register AMBTREE *at;
512	greg	2.26	int (*f)();
513	greg	2.20	{
514			register AMBVAL *av;
515			register int i;
516			/* transfer values at this node */
517			for (av = at->alist; av != NULL; av = at->alist) {
518			at->alist = av->next;
519	greg	2.26	(*f)(av);
520	greg	2.20	}
521	greg	2.21	if (at->kid == NULL)
522			return;
523	greg	2.20	for (i = 0; i < 8; i++) /* transfer and free children */
524	greg	2.26	unloadatree(at->kid+i, f);
525	greg	2.20	freeambtree(at->kid);
526	greg	2.26	at->kid = NULL;
527			}
528
529
530			static AMBVAL avlist1, avlist2; /* ambient value lists for sorting */
531			static int i_avlist; /* index for lists */
532
533
534			static
535			av2list(av)
536			AMBVAL *av;
537			{
538	greg	2.27	#ifdef DEBUG
539	greg	2.26	if (i_avlist >= nambvals)
540			error(CONSISTENCY, "too many ambient values in av2list1");
541	greg	2.27	#endif
542	greg	2.26	avlist1[i_avlist] = avlist2[i_avlist] = av;
543			i_avlist++;
544			}
545
546
547			static int
548			alatcmp(avp1, avp2) /* compare ambient values for MRA */
549			AMBVAL avp1, avp2;
550			{
551			return((avp2).latick - (avp1).latick);
552			}
553
554
555			static int
556			aposcmp(avp1, avp2) /* compare ambient value positions */
557			AMBVAL avp1, avp2;
558			{
559			return(avp1 - avp2);
560			}
561
562
563	greg	2.27	#ifdef DEBUG
564			static int
565			avlmemi(avaddr) /* find list position from address */
566			AMBVAL *avaddr;
567			{
568			register AMBVAL **avlpp;
569
570			avlpp = (AMBVAL *)bsearch((char )&avaddr, (char *)avlist2,
571			nambvals, sizeof(AMBVAL *), aposcmp);
572			if (avlpp == NULL)
573			error(CONSISTENCY, "address not found in avlmemi");
574			return(avlpp - avlist2);
575			}
576			#else
577			#define avlmemi(avaddr) ((AMBVAL *)bsearch((char )&avaddr,(char *)avlist2, \
578			nambvals,sizeof(AMBVAL *),aposcmp) - avlist2)
579			#endif
580
581
582	greg	2.26	static
583			sortambvals(always) /* resort ambient values */
584			int always;
585			{
586			AMBTREE oldatrunk;
587			AMBVAL tav, tap, pnext;
588			register int i, j;
589			/*
590			* The idea here is to minimize memory thrashing
591			* in VM systems by improving reference locality.
592			* We do this by periodically sorting our stored ambient
593			* values in memory in order of most recently to least
594			* recently accessed. This ordering was chosen so that new
595			* ambient values (which tend to be less important) go into
596			* higher memory with the infrequently accessed values.
597			* Since we expect our values to need sorting less
598			* frequently as the process continues, we double our
599			* waiting interval after each call.
600			* This routine is also called by setambacc() with
601			* the "always" parameter set to 1 so that the ambient
602			* tree will be rebuilt with the new accuracy parameter.
603			*/
604	greg	2.27	if (tracktime) { /* allocate pointer arrays to sort */
605	greg	2.26	avlist1 = (AMBVAL *)malloc(nambvalssizeof(AMBVAL *));
606			avlist2 = (AMBVAL *)malloc(nambvalssizeof(AMBVAL *));
607			} else
608			avlist1 = avlist2 = NULL;
609	greg	2.27	if (avlist2 == NULL) { /* no time tracking -- rebuild tree? */
610	greg	2.26	if (avlist1 != NULL)
611			free((char *)avlist1);
612	greg	2.27	if (always) { /* rebuild without sorting */
613			copystruct(&oldatrunk, &atrunk);
614			atrunk.alist = NULL;
615			atrunk.kid = NULL;
616			unloadatree(&oldatrunk, avinsert);
617			}
618	greg	2.26	} else { /* sort memory by last access time */
619			/*
620			* Sorting memory is tricky because it isn't contiguous.
621			* We have to sort an array of pointers by MRA and also
622			* by memory position. We then copy values in "loops"
623			* to minimize memory hits. Nevertheless, we will visit
624	greg	2.27	* everyone at least twice, and this is an expensive process
625	greg	2.26	* when we're thrashing, which is when we need to do it.
626			*/
627	greg	2.27	#ifdef DEBUG
628			sprintf(errmsg, "sorting %u ambient values...", nambvals);
629			eputs(errmsg);
630			#endif
631			i_avlist = 0;
632			unloadatree(&atrunk, av2list); /* empty current tree */
633			#ifdef DEBUG
634			if (i_avlist < nambvals)
635			error(CONSISTENCY, "missing ambient values in sortambvals");
636			#endif
637	greg	2.26	qsort((char )avlist1, nambvals, sizeof(AMBVAL ), alatcmp);
638			qsort((char )avlist2, nambvals, sizeof(AMBVAL ), aposcmp);
639			for (i = 0; i < nambvals; i++) {
640	greg	2.27	if (avlist1[i] == NULL)
641	greg	2.26	continue;
642			tap = avlist2[i];
643			copystruct(&tav, tap);
644			for (j = i; (pnext = avlist1[j]) != tap;
645	greg	2.27	j = avlmemi(pnext)) {
646	greg	2.26	copystruct(avlist2[j], pnext);
647			avinsert(avlist2[j]);
648			avlist1[j] = NULL;
649			}
650			copystruct(avlist2[j], &tav);
651			avinsert(avlist2[j]);
652			avlist1[j] = NULL;
653			}
654			free((char *)avlist1);
655			free((char *)avlist2);
656	greg	2.27	if (sortintvl < SORT_INTVL<<6)
657	greg	2.26	sortintvl <<= 1; /* wait twice as long next */
658	greg	2.27	#ifdef DEBUG
659			eputs("done\n");
660			#endif
661	greg	2.26	}
662			if (ambclock >= MAXACLOCK)
663			ambclock = MAXACLOCK/2;
664			lastsort = ambclock;
665	greg	2.20	}
666
667
668	greg	2.18	#ifdef F_SETLKW
669	greg	2.10
670	greg	2.19	static
671			aflock(typ) /* lock/unlock ambient file */
672			int typ;
673			{
674			static struct flock fls; /* static so initialized to zeroes */
675
676			fls.l_type = typ;
677			if (fcntl(fileno(ambfp), F_SETLKW, &fls) < 0)
678			error(SYSTEM, "cannot (un)lock ambient file");
679			}
680
681
682	greg	2.16	int
683	greg	2.7	ambsync() /* synchronize ambient file */
684			{
685			static FILE *ambinp = NULL;
686	greg	2.15	static long lastpos = -1;
687			long flen;
688	greg	2.12	AMBVAL avs;
689	greg	2.7	register int n;
690	greg	2.16
691			if (nunflshed == 0)
692			return(0);
693	greg	2.19	if (lastpos < 0) /* initializing (locked in initambfile) */
694			goto syncend;
695	greg	2.7	/* gain exclusive access */
696	greg	2.19	aflock(F_WRLCK);
697	greg	2.7	/* see if file has grown */
698	greg	2.15	if ((flen = lseek(fileno(ambfp), 0L, 2)) < 0)
699	greg	2.21	goto seekerr;
700	greg	2.15	if (n = flen - lastpos) { /* file has grown */
701	greg	2.17	if (ambinp == NULL) { /* use duplicate filedes */
702			ambinp = fdopen(dup(fileno(ambfp)), "r");
703	greg	2.14	if (ambinp == NULL)
704	greg	2.17	error(SYSTEM, "fdopen failed in ambsync");
705	greg	2.14	}
706	greg	2.15	if (fseek(ambinp, lastpos, 0) < 0)
707	greg	2.21	goto seekerr;
708	greg	2.15	while (n >= AMBVALSIZ) { /* load contributed values */
709	greg	2.7	readambval(&avs, ambinp);
710	greg	2.21	avinsert(avstore(&avs));
711	greg	2.15	n -= AMBVALSIZ;
712			}
713	greg	2.22	/*** seek always as safety measure
714			if (n) **/ / alignment */
715	greg	2.21	if (lseek(fileno(ambfp), flen-n, 0) < 0)
716			goto seekerr;
717	greg	2.7	}
718	greg	2.21	#ifdef DEBUG
719			if (ambfp->_ptr - ambfp->_base != nunflshed*AMBVALSIZ) {
720			sprintf(errmsg, "ambient file buffer at %d rather than %d",
721			ambfp->_ptr - ambfp->_base,
722			nunflshed*AMBVALSIZ);
723			error(CONSISTENCY, errmsg);
724			}
725			#endif
726	greg	2.15	syncend:
727	greg	2.7	n = fflush(ambfp); /* calls write() at last */
728	greg	2.21	if ((lastpos = lseek(fileno(ambfp), 0L, 1)) < 0)
729			goto seekerr;
730	greg	2.19	aflock(F_UNLCK); /* release file */
731	greg	2.16	nunflshed = 0;
732	greg	2.7	return(n);
733	greg	2.21	seekerr:
734			error(SYSTEM, "seek failed in ambsync");
735	greg	2.18	}
736
737			#else
738
739			int
740			ambsync() /* flush ambient file */
741			{
742			if (nunflshed == 0)
743			return(0);
744			nunflshed = 0;
745			return(fflush(ambfp));
746	greg	1.1	}
747	greg	2.10
748			#endif