/* Copyright (c) 1992 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "@(#)ambient.c 2.14 11/3/92 LBL";
#endif

/*
 *  ambient.c - routines dealing with ambient (inter-reflected) component.
 *
 *     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;
{
	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[];

#ifdef MSDOS
	setmode(fileno(ambfp), O_BINARY);
#endif
	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);
#ifndef	 NIX
		sync();			/* protect against NFS buffering */
#endif
	} 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  <sys/types.h>
#include  <sys/stat.h>

static
ambsync()			/* synchronize ambient file */
{
	static FILE  *ambinp = NULL;
	struct flock  fls;
	struct stat  sts;
#define	flen	sts.st_size
	AMBVAL	avs;
	long  lastpos;
	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");
	if (n = (flen - lastpos)/AMBVALSIZ) {	/* file has grown */
		if (ambinp == NULL) {		/* use duplicate file */
			ambinp = fdopen(dup(fileno(ambfp)), "r");
			if (ambinp == NULL)
				error(SYSTEM, "fdopen failed in ambsync");
		}
		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