src/rt/ambient.c

/* Copyright (c) 1991 Regents of the University of California */

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

/*
 *  ambient.c - routines dealing with ambient (inter-reflected) component.
 *
 *  The macro AMBFLUSH (if defined) is the number of ambient values
 *      to wait before flushing to the ambient file.
 *
 *     5/9/86
 */

#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 */

#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 */

#define  AMBFLUSH       (BUFSIZ/AMBVALSIZ)

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

#define  newambtree()   (AMBTREE *)calloc(8, sizeof(AMBTREE))

extern long  ftell(), lseek();
static int  initambfile(), avsave(), avinsert(), ambsync();


setambres(ar)                           /* set ambient resolution */
int  ar;
{
                                                /* set min & max radii */
        if (ar <= 0) {
                minarad = 0.0;
                maxarad = thescene.cusize / 2.0;
        } else {
                minarad = thescene.cusize / ar;
                maxarad = 16.0 * minarad;               /* heuristic */
                if (maxarad > thescene.cusize / 2.0)
                        maxarad = thescene.cusize / 2.0;
        }
        if (maxarad <= FTINY)
                maxarad = .001;
}


setambient(afile)                       /* initialize calculation */
char  *afile;
{
        long  headlen;
        AMBVAL  amb;
                                                /* init ambient limits */
        setambres(ambres);
                                                /* open ambient file */
        if (afile != NULL)
                if ((ambfp = fopen(afile, "r+")) != NULL) {
                        initambfile(0);
                        headlen = ftell(ambfp);
                        while (readambval(&amb, ambfp))
                                avinsert(&amb, &atrunk, thescene.cuorg,
                                                thescene.cusize);
                                                        /* 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);
                }
}


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;
        }
                                                /* 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;
{
        extern double  sqrt();
        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) {
                /*
                 *  Ambient level test.
                 */
                if (av->lvl > al || 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[];

        setbuf(ambfp, bmalloc(BUFSIZ));
        if (creat) {                    /* new file */
                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);
                fflush(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;
{
        static int  nunflshed = 0;

        avinsert(av, &atrunk, thescene.cuorg, thescene.cusize);
        if (ambfp == NULL)
                return;
        if (writambval(av, ambfp) < 0)
                goto writerr;
        if (++nunflshed >= AMBFLUSH) {
                if (ambsync() == EOF)
                        goto writerr;
                nunflshed = 0;
        }
        return;
writerr:
        error(SYSTEM, "error writing ambient file");
}


static
avinsert(aval, at, c0, s)               /* insert ambient value in a tree */
AMBVAL  *aval;
register AMBTREE  *at;
FVECT  c0;
double  s;
{
        FVECT  ck0;
        int  branch;
        register AMBVAL  *av;
        register int  i;

        if ((av = newambval()) == NULL)
                goto memerr;
        copystruct(av, aval);
        VCOPY(ck0, c0);
        while (s*(OCTSCALE/2) > av->rad*ambacc) {
                if (at->kid == NULL)
                        if ((at->kid = newambtree()) == NULL)
                                goto memerr;
                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;
        }
        av->next = at->alist;
        at->alist = av;
        return;
memerr:
        error(SYSTEM, "out of memory in avinsert");
}


#ifdef  NIX

static
ambsync()                       /* flush ambient file */
{
        return(fflush(ambfp));
}

#else

#include  <fcntl.h>
#include  <sys/types.h>
#include  <sys/stat.h>

static
ambsync()                       /* synchronize ambient file */
{
        static FILE  *ambinp = NULL;
        struct flock  fls;
        struct stat  sts;
        AMBVAL  avs;
        long  lastpos, flen;
        register int  n;
                                /* gain exclusive access */
        fls.l_type = F_WRLCK;
        fls.l_whence = 0;
        fls.l_start = 0L;
        fls.l_len = 0L;
        if (fcntl(fileno(ambfp), F_SETLKW, &fls) < 0)
                error(SYSTEM, "cannot lock ambient file");
                                /* see if file has grown */
        lastpos = lseek(fileno(ambfp), 0L, 1);  /* get previous position */
        if (fstat(fileno(ambfp), &sts) < 0)     /* get current length */
                error(SYSTEM, "cannot stat ambient file");
        flen = sts.st_size;
        if (n = (flen - lastpos)/AMBVALSIZ) {   /* file has grown */
                if (ambinp == NULL)             /* use duplicate file */
                        ambinp = fdopen(dup(fileno(ambfp)), "r");
                while (n--) {                   /* load contributed values */
                        readambval(&avs, ambinp);
                        avinsert(&avs,&atrunk,thescene.cuorg,thescene.cusize);
                }                               /* moves shared file pointer */
                if (n = (flen - lastpos)%AMBVALSIZ)     /* alignment */
                        lseek(fileno(ambfp), flen-n, 0);
        }
        n = fflush(ambfp);                      /* calls write() at last */
        fls.l_type = F_UNLCK;                   /* release file */
        fcntl(fileno(ambfp), F_SETLKW, &fls);
        return(n);
}

#endif
Revision:	2.10
Committed:	Thu Jul 16 16:47:28 1992 UTC (31 years, 9 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.9:	+28 -16 lines
Log Message:	made ambsync() more efficient with use of duplicate file descriptor
#	User	Rev	Content
1	greg	1.14	/* Copyright (c) 1991 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			* The macro AMBFLUSH (if defined) is the number of ambient values
11			* to wait before flushing to the ambient file.
12			*
13			* 5/9/86
14			*/
15
16			#include "ray.h"
17
18			#include "octree.h"
19
20	greg	1.8	#include "otypes.h"
21
22	greg	1.14	#include "ambient.h"
23
24	greg	1.1	#include "random.h"
25
26			#define OCTSCALE 0.5 /* ceil((valid rad.)/(cube size)) */
27
28	greg	1.14	typedef struct ambtree {
29			AMBVAL alist; / ambient value list */
30			struct ambtree kid; / 8 child nodes */
31			} AMBTREE; /* ambient octree */
32
33	greg	1.1	extern CUBE thescene; /* contains space boundaries */
34
35	greg	1.11	#define MAXASET 511 /* maximum number of elements in ambient set */
36			OBJECT ambset[MAXASET+1]={0}; /* ambient include/exclude set */
37	greg	1.1
38			double maxarad; /* maximum ambient radius */
39			double minarad; /* minimum ambient radius */
40
41			static AMBTREE atrunk; /* our ambient trunk node */
42
43			static FILE ambfp = NULL; / ambient file pointer */
44
45	greg	2.6	#define AMBFLUSH (BUFSIZ/AMBVALSIZ)
46
47	greg	1.1	#define newambval() (AMBVAL *)bmalloc(sizeof(AMBVAL))
48
49			#define newambtree() (AMBTREE *)calloc(8, sizeof(AMBTREE))
50
51	greg	2.7	extern long ftell(), lseek();
52	greg	2.10	static int initambfile(), avsave(), avinsert(), ambsync();
53	greg	1.1
54	greg	2.7
55	greg	2.3	setambres(ar) /* set ambient resolution */
56			int ar;
57			{
58			/* set min & max radii */
59			if (ar <= 0) {
60			minarad = 0.0;
61			maxarad = thescene.cusize / 2.0;
62			} else {
63			minarad = thescene.cusize / ar;
64			maxarad = 16.0 * minarad; /* heuristic */
65			if (maxarad > thescene.cusize / 2.0)
66			maxarad = thescene.cusize / 2.0;
67			}
68	greg	2.4	if (maxarad <= FTINY)
69			maxarad = .001;
70	greg	2.3	}
71
72
73	greg	1.1	setambient(afile) /* initialize calculation */
74			char *afile;
75			{
76	greg	2.9	long headlen;
77	greg	1.1	AMBVAL amb;
78	greg	2.3	/* init ambient limits */
79			setambres(ambres);
80			/* open ambient file */
81	greg	2.10	if (afile != NULL)
82	greg	1.1	if ((ambfp = fopen(afile, "r+")) != NULL) {
83	greg	2.6	initambfile(0);
84	greg	2.9	headlen = ftell(ambfp);
85	greg	2.5	while (readambval(&amb, ambfp))
86	greg	1.1	avinsert(&amb, &atrunk, thescene.cuorg,
87			thescene.cusize);
88			/* align */
89	greg	2.9	fseek(ambfp, -((ftell(ambfp)-headlen)%AMBVALSIZ), 1);
90	greg	2.10	} else if ((ambfp = fopen(afile, "w+")) != NULL)
91	greg	2.6	initambfile(1);
92			else {
93	greg	1.1	sprintf(errmsg, "cannot open ambient file \"%s\"",
94			afile);
95			error(SYSTEM, errmsg);
96	greg	1.8	}
97			}
98
99
100			ambnotify(obj) /* record new modifier */
101			OBJECT obj;
102			{
103	greg	1.11	static int hitlimit = 0;
104	greg	1.8	register OBJREC *o = objptr(obj);
105			register char **amblp;
106
107	greg	1.11	if (hitlimit \|\| !ismodifier(o->otype))
108	greg	1.8	return;
109			for (amblp = amblist; *amblp != NULL; amblp++)
110			if (!strcmp(o->oname, *amblp)) {
111	greg	1.11	if (ambset[0] >= MAXASET) {
112			error(WARNING, "too many modifiers in ambient list");
113			hitlimit++;
114			return; /* should this be fatal? */
115			}
116	greg	1.8	insertelem(ambset, obj);
117			return;
118	greg	1.1	}
119			}
120
121
122			ambient(acol, r) /* compute ambient component for ray */
123			COLOR acol;
124			register RAY *r;
125			{
126			static int rdepth = 0; /* ambient recursion */
127	greg	1.16	double d;
128	greg	1.1
129			if (ambdiv <= 0) /* no ambient calculation */
130			goto dumbamb;
131			/* check number of bounces */
132	greg	1.16	if (rdepth >= ambounce)
133	greg	1.1	goto dumbamb;
134			/* check ambient list */
135			if (ambincl != -1 && r->ro != NULL &&
136			ambincl != inset(ambset, r->ro->omod))
137			goto dumbamb;
138
139			if (ambacc <= FTINY) { /* no ambient storage */
140	greg	1.16	rdepth++;
141			d = doambient(acol, r, r->rweight, NULL, NULL);
142			rdepth--;
143			if (d == 0.0)
144	greg	1.1	goto dumbamb;
145	greg	1.16	return;
146	greg	1.1	}
147			/* get ambient value */
148			setcolor(acol, 0.0, 0.0, 0.0);
149	greg	1.16	d = sumambient(acol, r, rdepth,
150			&atrunk, thescene.cuorg, thescene.cusize);
151			if (d > FTINY)
152			scalecolor(acol, 1.0/d);
153			else {
154			d = makeambient(acol, r, rdepth++);
155			rdepth--;
156			}
157			if (d > FTINY)
158			return;
159	greg	1.1	dumbamb: /* return global value */
160			copycolor(acol, ambval);
161			}
162
163
164			double
165	greg	1.16	sumambient(acol, r, al, at, c0, s) /* get interpolated ambient value */
166	greg	1.1	COLOR acol;
167			register RAY *r;
168	greg	1.16	int al;
169	greg	1.1	AMBTREE *at;
170			FVECT c0;
171			double s;
172			{
173			extern double sqrt();
174			double d, e1, e2, wt, wsum;
175			COLOR ct;
176			FVECT ck0;
177			int i;
178			register int j;
179			register AMBVAL *av;
180	greg	1.7	/* do this node */
181	greg	1.1	wsum = 0.0;
182			for (av = at->alist; av != NULL; av = av->next) {
183			/*
184	greg	1.16	* Ambient level test.
185	greg	1.1	*/
186	greg	1.16	if (av->lvl > al \|\| av->weight < r->rweight-FTINY)
187	greg	1.1	continue;
188			/*
189			* Ambient radius test.
190			*/
191			e1 = 0.0;
192			for (j = 0; j < 3; j++) {
193			d = av->pos[j] - r->rop[j];
194			e1 += d * d;
195			}
196			e1 /= av->rad * av->rad;
197			if (e1 > ambaccambacc1.21)
198			continue;
199			/*
200			* Normal direction test.
201			*/
202			e2 = (1.0 - DOT(av->dir, r->ron)) * r->rweight;
203			if (e2 < 0.0) e2 = 0.0;
204			if (e1 + e2 > ambaccambacc1.21)
205			continue;
206			/*
207			* Ray behind test.
208			*/
209			d = 0.0;
210			for (j = 0; j < 3; j++)
211			d += (r->rop[j] - av->pos[j]) *
212			(av->dir[j] + r->ron[j]);
213	greg	1.18	if (d0.5 < -minaradambacc-.001)
214	greg	1.1	continue;
215			/*
216			* Jittering final test reduces image artifacts.
217			*/
218			wt = sqrt(e1) + sqrt(e2);
219	greg	2.2	wt = .9 + .2urand(9015+samplendx);
220	greg	1.6	if (wt > ambacc)
221	greg	1.1	continue;
222			if (wt <= 1e-3)
223			wt = 1e3;
224			else
225			wt = 1.0 / wt;
226			wsum += wt;
227	greg	1.15	extambient(ct, av, r->rop, r->ron);
228	greg	1.1	scalecolor(ct, wt);
229			addcolor(acol, ct);
230	greg	1.7	}
231			if (at->kid == NULL)
232			return(wsum);
233			/* do children */
234			s *= 0.5;
235			for (i = 0; i < 8; i++) {
236			for (j = 0; j < 3; j++) {
237			ck0[j] = c0[j];
238			if (1<<j & i)
239			ck0[j] += s;
240			if (r->rop[j] < ck0[j] - OCTSCALE*s)
241			break;
242			if (r->rop[j] > ck0[j] + (1.0+OCTSCALE)*s)
243			break;
244			}
245			if (j == 3)
246	greg	1.16	wsum += sumambient(acol, r, al, at->kid+i, ck0, s);
247	greg	1.1	}
248			return(wsum);
249			}
250
251
252			double
253	greg	1.16	makeambient(acol, r, al) /* make a new ambient value */
254	greg	1.1	COLOR acol;
255			register RAY *r;
256	greg	1.16	int al;
257	greg	1.1	{
258			AMBVAL amb;
259	greg	1.14	FVECT gp, gd;
260	greg	1.16	/* compute weight */
261			amb.weight = pow(AVGREFL, (double)al);
262	greg	1.17	if (r->rweight < 0.2amb.weight) / heuristic */
263	greg	1.16	amb.weight = r->rweight;
264			/* compute ambient */
265			amb.rad = doambient(acol, r, amb.weight, gp, gd);
266	greg	1.1	if (amb.rad == 0.0)
267			return(0.0);
268			/* store it */
269			VCOPY(amb.pos, r->rop);
270			VCOPY(amb.dir, r->ron);
271	greg	1.16	amb.lvl = al;
272	greg	1.1	copycolor(amb.val, acol);
273	greg	1.14	VCOPY(amb.gpos, gp);
274			VCOPY(amb.gdir, gd);
275	greg	1.1	/* insert into tree */
276	greg	2.7	avsave(&amb); /* and save to file */
277	greg	1.1	return(amb.rad);
278	greg	1.15	}
279
280
281			extambient(cr, ap, pv, nv) /* extrapolate value at pv, nv */
282			COLOR cr;
283			register AMBVAL *ap;
284			FVECT pv, nv;
285			{
286			FVECT v1, v2;
287			register int i;
288			double d;
289
290			d = 1.0; /* zeroeth order */
291			/* gradient due to translation */
292			for (i = 0; i < 3; i++)
293			d += ap->gpos[i]*(pv[i]-ap->pos[i]);
294			/* gradient due to rotation */
295			VCOPY(v1, ap->dir);
296			fcross(v2, v1, nv);
297			d += DOT(ap->gdir, v2);
298			if (d <= 0.0) {
299			setcolor(cr, 0.0, 0.0, 0.0);
300			return;
301			}
302			copycolor(cr, ap->val);
303			scalecolor(cr, d);
304	greg	1.1	}
305
306
307			static
308	greg	2.9	initambfile(creat) /* initialize ambient file */
309			int creat;
310			{
311			extern char progname, octname, VersionID[];
312
313			setbuf(ambfp, bmalloc(BUFSIZ));
314			if (creat) { /* new file */
315			fprintf(ambfp, "%s -av %g %g %g -ab %d -aa %g ",
316			progname, colval(ambval,RED),
317			colval(ambval,GRN), colval(ambval,BLU),
318			ambounce, ambacc);
319			fprintf(ambfp, "-ad %d -as %d -ar %d %s\n",
320			ambdiv, ambssamp, ambres,
321			octname==NULL ? "" : octname);
322			fprintf(ambfp, "SOFTWARE= %s\n", VersionID);
323			fputformat(AMBFMT, ambfp);
324			putc('\n', ambfp);
325			putambmagic(ambfp);
326			fflush(ambfp);
327	greg	2.10	} else if (checkheader(ambfp, AMBFMT, NULL) < 0 \|\| !hasambmagic(ambfp))
328			error(USER, "bad ambient file");
329	greg	2.9	}
330
331
332			static
333	greg	2.7	avsave(av) /* insert and save an ambient value */
334	greg	1.1	AMBVAL *av;
335			{
336			static int nunflshed = 0;
337	greg	2.6
338	greg	2.7	avinsert(av, &atrunk, thescene.cuorg, thescene.cusize);
339	greg	1.1	if (ambfp == NULL)
340			return;
341	greg	2.5	if (writambval(av, ambfp) < 0)
342	greg	1.1	goto writerr;
343			if (++nunflshed >= AMBFLUSH) {
344	greg	2.7	if (ambsync() == EOF)
345	greg	1.1	goto writerr;
346			nunflshed = 0;
347			}
348			return;
349			writerr:
350			error(SYSTEM, "error writing ambient file");
351			}
352
353
354			static
355			avinsert(aval, at, c0, s) /* insert ambient value in a tree */
356			AMBVAL *aval;
357			register AMBTREE *at;
358			FVECT c0;
359			double s;
360			{
361			FVECT ck0;
362			int branch;
363			register AMBVAL *av;
364			register int i;
365
366			if ((av = newambval()) == NULL)
367			goto memerr;
368	greg	1.9	copystruct(av, aval);
369	greg	1.1	VCOPY(ck0, c0);
370			while (s(OCTSCALE/2) > av->radambacc) {
371			if (at->kid == NULL)
372			if ((at->kid = newambtree()) == NULL)
373			goto memerr;
374			s *= 0.5;
375			branch = 0;
376			for (i = 0; i < 3; i++)
377			if (av->pos[i] > ck0[i] + s) {
378			ck0[i] += s;
379			branch \|= 1 << i;
380			}
381			at = at->kid + branch;
382			}
383			av->next = at->alist;
384			at->alist = av;
385			return;
386			memerr:
387			error(SYSTEM, "out of memory in avinsert");
388	greg	2.7	}
389
390
391	greg	2.10	#ifdef NIX
392
393			static
394			ambsync() /* flush ambient file */
395			{
396			return(fflush(ambfp));
397			}
398
399			#else
400
401	greg	2.7	#include <fcntl.h>
402	greg	2.10	#include <sys/types.h>
403			#include <sys/stat.h>
404	greg	2.7
405			static
406			ambsync() /* synchronize ambient file */
407			{
408			static FILE *ambinp = NULL;
409			struct flock fls;
410	greg	2.10	struct stat sts;
411	greg	2.7	AMBVAL avs;
412			long lastpos, flen;
413			register int n;
414			/* gain exclusive access */
415			fls.l_type = F_WRLCK;
416			fls.l_whence = 0;
417			fls.l_start = 0L;
418			fls.l_len = 0L;
419			if (fcntl(fileno(ambfp), F_SETLKW, &fls) < 0)
420			error(SYSTEM, "cannot lock ambient file");
421			/* see if file has grown */
422	greg	2.9	lastpos = lseek(fileno(ambfp), 0L, 1); /* get previous position */
423	greg	2.10	if (fstat(fileno(ambfp), &sts) < 0) /* get current length */
424			error(SYSTEM, "cannot stat ambient file");
425			flen = sts.st_size;
426	greg	2.7	if (n = (flen - lastpos)/AMBVALSIZ) { /* file has grown */
427	greg	2.10	if (ambinp == NULL) /* use duplicate file */
428			ambinp = fdopen(dup(fileno(ambfp)), "r");
429	greg	2.7	while (n--) { /* load contributed values */
430			readambval(&avs, ambinp);
431			avinsert(&avs,&atrunk,thescene.cuorg,thescene.cusize);
432	greg	2.10	} /* moves shared file pointer */
433			if (n = (flen - lastpos)%AMBVALSIZ) /* alignment */
434			lseek(fileno(ambfp), flen-n, 0);
435	greg	2.7	}
436			n = fflush(ambfp); /* calls write() at last */
437			fls.l_type = F_UNLCK; /* release file */
438			fcntl(fileno(ambfp), F_SETLKW, &fls);
439			return(n);
440	greg	1.1	}
441	greg	2.10
442			#endif