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 */
static char  *afname;           /* ambient file name */
static long  ambheadlen;        /* length of ambient file header */

#define  AMBFLUSH       (BUFSIZ/AMBVALSIZ)

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

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

extern long  ftell(), lseek();


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;
{
        AMBVAL  amb;
                                                /* init ambient limits */
        setambres(ambres);
                                                /* open ambient file */
        if ((afname = afile) != NULL)
                if ((ambfp = fopen(afile, "r+")) != NULL) {
                        initambfile(0);
                        while (readambval(&amb, ambfp))
                                avinsert(&amb, &atrunk, thescene.cuorg,
                                                thescene.cusize);
                                                        /* align */
                        fseek(ambfp, -((ftell(ambfp)-ambheadlen)%AMBVALSIZ), 1);
                } else if ((ambfp = fopen(afile, "w")) != NULL)
                        initambfile(1);
                else {
                        sprintf(errmsg, "cannot open ambient file \"%s\"",
                                        afile);
                        error(SYSTEM, errmsg);
                }
}


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

        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);
                fputformat(AMBFMT, ambfp);
                putc('\n', ambfp);
                putambmagic(ambfp);
                fflush(ambfp);
        } else if (checkheader(ambfp, AMBFMT, NULL) < 0
                        || !hasambmagic(ambfp)) {
                sprintf(errmsg, "\"%s\" is not an ambient file", afname);
                error(USER, afname);
        }
        ambheadlen = ftell(ambfp);
}


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
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");
}


#include  <fcntl.h>


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