src/rt/ambcomp.c

#ifndef lint
static const char       RCSid[] = "$Id$";
#endif
/*
 * Routines to compute "ambient" values using Monte Carlo
 *
 *  Declarations of external symbols in ambient.h
 */

/* ====================================================================
 * The Radiance Software License, Version 1.0
 *
 * Copyright (c) 1990 - 2002 The Regents of the University of California,
 * through Lawrence Berkeley National Laboratory.   All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *         notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in
 *       the documentation and/or other materials provided with the
 *       distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *           if any, must include the following acknowledgment:
 *             "This product includes Radiance software
 *                 (http://radsite.lbl.gov/)
 *                 developed by the Lawrence Berkeley National Laboratory
 *               (http://www.lbl.gov/)."
 *       Alternately, this acknowledgment may appear in the software itself,
 *       if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
 *       and "The Regents of the University of California" must
 *       not be used to endorse or promote products derived from this
 *       software without prior written permission. For written
 *       permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Radiance",
 *       nor may "Radiance" appear in their name, without prior written
 *       permission of Lawrence Berkeley National Laboratory.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.   IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Lawrence Berkeley National Laboratory.   For more
 * information on Lawrence Berkeley National Laboratory, please see
 * <http://www.lbl.gov/>.
 */

#include  "ray.h"

#include  "ambient.h"

#include  "random.h"


static int
ambcmp(d1, d2)                          /* decreasing order */
AMBSAMP  *d1, *d2;
{
        if (d1->k < d2->k)
                return(1);
        if (d1->k > d2->k)
                return(-1);
        return(0);
}


static int
ambnorm(d1, d2)                         /* standard order */
AMBSAMP  *d1, *d2;
{
        register int  c;

        if (c = d1->t - d2->t)
                return(c);
        return(d1->p - d2->p);
}


int
divsample(dp, h, r)                     /* sample a division */
register AMBSAMP  *dp;
AMBHEMI  *h;
RAY  *r;
{
        RAY  ar;
        int  hlist[3];
        double  spt[2];
        double  xd, yd, zd;
        double  b2;
        double  phi;
        register int  i;

        if (rayorigin(&ar, r, AMBIENT, AVGREFL) < 0)
                return(-1);
        hlist[0] = r->rno;
        hlist[1] = dp->t;
        hlist[2] = dp->p;
        multisamp(spt, 2, urand(ilhash(hlist,3)+dp->n));
        zd = sqrt((dp->t + spt[0])/h->nt);
        phi = 2.0*PI * (dp->p + spt[1])/h->np;
        xd = tcos(phi) * zd;
        yd = tsin(phi) * zd;
        zd = sqrt(1.0 - zd*zd);
        for (i = 0; i < 3; i++)
                ar.rdir[i] =    xd*h->ux[i] +
                                yd*h->uy[i] +
                                zd*h->uz[i];
        dimlist[ndims++] = dp->t*h->np + dp->p + 90171;
        rayvalue(&ar);
        ndims--;
        addcolor(dp->v, ar.rcol);
                                        /* use rt to improve gradient calc */
        if (ar.rt > FTINY && ar.rt < FHUGE)
                dp->r += 1.0/ar.rt;
                                        /* (re)initialize error */
        if (dp->n++) {
                b2 = bright(dp->v)/dp->n - bright(ar.rcol);
                b2 = b2*b2 + dp->k*((dp->n-1)*(dp->n-1));
                dp->k = b2/(dp->n*dp->n);
        } else
                dp->k = 0.0;
        return(0);
}


double
doambient(acol, r, wt, pg, dg)          /* compute ambient component */
COLOR  acol;
RAY  *r;
double  wt;
FVECT  pg, dg;
{
        double  b, d;
        AMBHEMI  hemi;
        AMBSAMP  *div;
        AMBSAMP  dnew;
        register AMBSAMP  *dp;
        double  arad;
        int  ndivs, ns;
        register int  i, j;
                                        /* initialize color */
        setcolor(acol, 0.0, 0.0, 0.0);
                                        /* initialize hemisphere */
        inithemi(&hemi, r, wt);
        ndivs = hemi.nt * hemi.np;
        if (ndivs == 0)
                return(0.0);
                                        /* set number of super-samples */
        ns = ambssamp * wt + 0.5;
        if (ns > 0 || pg != NULL || dg != NULL) {
                div = (AMBSAMP *)malloc(ndivs*sizeof(AMBSAMP));
                if (div == NULL)
                        error(SYSTEM, "out of memory in doambient");
        } else
                div = NULL;
                                        /* sample the divisions */
        arad = 0.0;
        if ((dp = div) == NULL)
                dp = &dnew;
        for (i = 0; i < hemi.nt; i++)
                for (j = 0; j < hemi.np; j++) {
                        dp->t = i; dp->p = j;
                        setcolor(dp->v, 0.0, 0.0, 0.0);
                        dp->r = 0.0;
                        dp->n = 0;
                        if (divsample(dp, &hemi, r) < 0)
                                goto oopsy;
                        arad += dp->r;
                        if (div != NULL)
                                dp++;
                        else
                                addcolor(acol, dp->v);
                }
        if (ns > 0 && arad > FTINY && ndivs/arad < minarad)
                ns = 0;                 /* close enough */
        else if (ns > 0) {              /* else perform super-sampling */
                comperrs(div, &hemi);                   /* compute errors */
                qsort(div, ndivs, sizeof(AMBSAMP), ambcmp);     /* sort divs */
                                                /* super-sample */
                for (i = ns; i > 0; i--) {
                        copystruct(&dnew, div);
                        if (divsample(&dnew, &hemi, r) < 0)
                                goto oopsy;
                                                        /* reinsert */
                        dp = div;
                        j = ndivs < i ? ndivs : i;
                        while (--j > 0 && dnew.k < dp[1].k) {
                                copystruct(dp, dp+1);
                                dp++;
                        }
                        copystruct(dp, &dnew);
                }
                if (pg != NULL || dg != NULL)   /* restore order */
                        qsort(div, ndivs, sizeof(AMBSAMP), ambnorm);
        }
                                        /* compute returned values */
        if (div != NULL) {
                arad = 0.0;
                for (i = ndivs, dp = div; i-- > 0; dp++) {
                        arad += dp->r;
                        if (dp->n > 1) {
                                b = 1.0/dp->n;
                                scalecolor(dp->v, b);
                                dp->r *= b;
                                dp->n = 1;
                        }
                        addcolor(acol, dp->v);
                }
                b = bright(acol);
                if (b > FTINY) {
                        b = ndivs/b;
                        if (pg != NULL) {
                                posgradient(pg, div, &hemi);
                                for (i = 0; i < 3; i++)
                                        pg[i] *= b;
                        }
                        if (dg != NULL) {
                                dirgradient(dg, div, &hemi);
                                for (i = 0; i < 3; i++)
                                        dg[i] *= b;
                        }
                } else {
                        if (pg != NULL)
                                for (i = 0; i < 3; i++)
                                        pg[i] = 0.0;
                        if (dg != NULL)
                                for (i = 0; i < 3; i++)
                                        dg[i] = 0.0;
                }
                free((void *)div);
        }
        b = 1.0/ndivs;
        scalecolor(acol, b);
        if (arad <= FTINY)
                arad = maxarad;
        else
                arad = (ndivs+ns)/arad;
        if (pg != NULL) {               /* reduce radius if gradient large */
                d = DOT(pg,pg);
                if (d*arad*arad > 1.0)
                        arad = 1.0/sqrt(d);
        }
        if (arad < minarad) {
                arad = minarad;
                if (pg != NULL && d*arad*arad > 1.0) {  /* cap gradient */
                        d = 1.0/arad/sqrt(d);
                        for (i = 0; i < 3; i++)
                                pg[i] *= d;
                }
        }
        if ((arad /= sqrt(wt)) > maxarad)
                arad = maxarad;
        return(arad);
oopsy:
        if (div != NULL)
                free((void *)div);
        return(0.0);
}


void
inithemi(hp, r, wt)             /* initialize sampling hemisphere */
register AMBHEMI  *hp;
RAY  *r;
double  wt;
{
        register int  i;
                                        /* set number of divisions */
        if (wt < (.25*PI)/ambdiv+FTINY) {
                hp->nt = hp->np = 0;
                return;                 /* zero samples */
        }
        hp->nt = sqrt(ambdiv * wt / PI) + 0.5;
        hp->np = PI * hp->nt + 0.5;
                                        /* make axes */
        VCOPY(hp->uz, r->ron);
        hp->uy[0] = hp->uy[1] = hp->uy[2] = 0.0;
        for (i = 0; i < 3; i++)
                if (hp->uz[i] < 0.6 && hp->uz[i] > -0.6)
                        break;
        if (i >= 3)
                error(CONSISTENCY, "bad ray direction in inithemi");
        hp->uy[i] = 1.0;
        fcross(hp->ux, hp->uy, hp->uz);
        normalize(hp->ux);
        fcross(hp->uy, hp->uz, hp->ux);
}


void
comperrs(da, hp)                /* compute initial error estimates */
AMBSAMP  *da;           /* assumes standard ordering */
register AMBHEMI  *hp;
{
        double  b, b2;
        int  i, j;
        register AMBSAMP  *dp;
                                /* sum differences from neighbors */
        dp = da;
        for (i = 0; i < hp->nt; i++)
                for (j = 0; j < hp->np; j++) {
#ifdef  DEBUG
                        if (dp->t != i || dp->p != j)
                                error(CONSISTENCY,
                                        "division order in comperrs");
#endif
                        b = bright(dp[0].v);
                        if (i > 0) {            /* from above */
                                b2 = bright(dp[-hp->np].v) - b;
                                b2 *= b2 * 0.25;
                                dp[0].k += b2;
                                dp[-hp->np].k += b2;
                        }
                        if (j > 0) {            /* from behind */
                                b2 = bright(dp[-1].v) - b;
                                b2 *= b2 * 0.25;
                                dp[0].k += b2;
                                dp[-1].k += b2;
                        } else {                /* around */
                                b2 = bright(dp[hp->np-1].v) - b;
                                b2 *= b2 * 0.25;
                                dp[0].k += b2;
                                dp[hp->np-1].k += b2;
                        }
                        dp++;
                }
                                /* divide by number of neighbors */
        dp = da;
        for (j = 0; j < hp->np; j++)            /* top row */
                (dp++)->k *= 1.0/3.0;
        if (hp->nt < 2)
                return;
        for (i = 1; i < hp->nt-1; i++)          /* central region */
                for (j = 0; j < hp->np; j++)
                        (dp++)->k *= 0.25;
        for (j = 0; j < hp->np; j++)            /* bottom row */
                (dp++)->k *= 1.0/3.0;
}


void
posgradient(gv, da, hp)                         /* compute position gradient */
FVECT  gv;
AMBSAMP  *da;                   /* assumes standard ordering */
register AMBHEMI  *hp;
{
        register int  i, j;
        double  nextsine, lastsine, b, d;
        double  mag0, mag1;
        double  phi, cosp, sinp, xd, yd;
        register AMBSAMP  *dp;

        xd = yd = 0.0;
        for (j = 0; j < hp->np; j++) {
                dp = da + j;
                mag0 = mag1 = 0.0;
                lastsine = 0.0;
                for (i = 0; i < hp->nt; i++) {
#ifdef  DEBUG
                        if (dp->t != i || dp->p != j)
                                error(CONSISTENCY,
                                        "division order in posgradient");
#endif
                        b = bright(dp->v);
                        if (i > 0) {
                                d = dp[-hp->np].r;
                                if (dp[0].r > d) d = dp[0].r;
                                                        /* sin(t)*cos(t)^2 */
                                d *= lastsine * (1.0 - (double)i/hp->nt);
                                mag0 += d*(b - bright(dp[-hp->np].v));
                        }
                        nextsine = sqrt((double)(i+1)/hp->nt);
                        if (j > 0) {
                                d = dp[-1].r;
                                if (dp[0].r > d) d = dp[0].r;
                                mag1 += d * (nextsine - lastsine) *
                                                (b - bright(dp[-1].v));
                        } else {
                                d = dp[hp->np-1].r;
                                if (dp[0].r > d) d = dp[0].r;
                                mag1 += d * (nextsine - lastsine) *
                                                (b - bright(dp[hp->np-1].v));
                        }
                        dp += hp->np;
                        lastsine = nextsine;
                }
                mag0 *= 2.0*PI / hp->np;
                phi = 2.0*PI * (double)j/hp->np;
                cosp = tcos(phi); sinp = tsin(phi);
                xd += mag0*cosp - mag1*sinp;
                yd += mag0*sinp + mag1*cosp;
        }
        for (i = 0; i < 3; i++)
                gv[i] = (xd*hp->ux[i] + yd*hp->uy[i])/PI;
}


void
dirgradient(gv, da, hp)                         /* compute direction gradient */
FVECT  gv;
AMBSAMP  *da;                   /* assumes standard ordering */
register AMBHEMI  *hp;
{
        register int  i, j;
        double  mag;
        double  phi, xd, yd;
        register AMBSAMP  *dp;

        xd = yd = 0.0;
        for (j = 0; j < hp->np; j++) {
                dp = da + j;
                mag = 0.0;
                for (i = 0; i < hp->nt; i++) {
#ifdef  DEBUG
                        if (dp->t != i || dp->p != j)
                                error(CONSISTENCY,
                                        "division order in dirgradient");
#endif
                                                        /* tan(t) */
                        mag += bright(dp->v)/sqrt(hp->nt/(i+.5) - 1.0);
                        dp += hp->np;
                }
                phi = 2.0*PI * (j+.5)/hp->np + PI/2.0;
                xd += mag * tcos(phi);
                yd += mag * tsin(phi);
        }
        for (i = 0; i < 3; i++)
                gv[i] = (xd*hp->ux[i] + yd*hp->uy[i])/(hp->nt*hp->np);
}
Revision:	2.9
Committed:	Sat Feb 22 02:07:28 2003 UTC (21 years, 2 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.8:	+70 -22 lines
Log Message:	Changes and check-in for 3.5 release Includes new source files and modifications not recorded for many years See ray/doc/notes/ReleaseNotes for notes between 3.1 and 3.5 release
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.9	static const char RCSid[] = "$Id$";
3	greg	1.1	#endif
4			/*
5			* Routines to compute "ambient" values using Monte Carlo
6	greg	2.9	*
7			* Declarations of external symbols in ambient.h
8			*/
9
10			/* ====================================================================
11			* The Radiance Software License, Version 1.0
12			*
13			* Copyright (c) 1990 - 2002 The Regents of the University of California,
14			* through Lawrence Berkeley National Laboratory. All rights reserved.
15			*
16			* Redistribution and use in source and binary forms, with or without
17			* modification, are permitted provided that the following conditions
18			* are met:
19			*
20			* 1. Redistributions of source code must retain the above copyright
21			* notice, this list of conditions and the following disclaimer.
22			*
23			* 2. Redistributions in binary form must reproduce the above copyright
24			* notice, this list of conditions and the following disclaimer in
25			* the documentation and/or other materials provided with the
26			* distribution.
27			*
28			* 3. The end-user documentation included with the redistribution,
29			* if any, must include the following acknowledgment:
30			* "This product includes Radiance software
31			* (http://radsite.lbl.gov/)
32			* developed by the Lawrence Berkeley National Laboratory
33			* (http://www.lbl.gov/)."
34			* Alternately, this acknowledgment may appear in the software itself,
35			* if and wherever such third-party acknowledgments normally appear.
36			*
37			* 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
38			* and "The Regents of the University of California" must
39			* not be used to endorse or promote products derived from this
40			* software without prior written permission. For written
41			* permission, please contact [email protected].
42			*
43			* 5. Products derived from this software may not be called "Radiance",
44			* nor may "Radiance" appear in their name, without prior written
45			* permission of Lawrence Berkeley National Laboratory.
46			*
47			* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
48			* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
49			* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
50			* DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
51			* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
52			* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
53			* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
54			* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
55			* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
56			* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
57			* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
58			* SUCH DAMAGE.
59			* ====================================================================
60			*
61			* This software consists of voluntary contributions made by many
62			* individuals on behalf of Lawrence Berkeley National Laboratory. For more
63			* information on Lawrence Berkeley National Laboratory, please see
64			* <http://www.lbl.gov/>.
65	greg	1.1	*/
66
67			#include "ray.h"
68
69			#include "ambient.h"
70
71			#include "random.h"
72
73
74			static int
75			ambcmp(d1, d2) /* decreasing order */
76			AMBSAMP d1, d2;
77			{
78			if (d1->k < d2->k)
79			return(1);
80			if (d1->k > d2->k)
81			return(-1);
82			return(0);
83			}
84
85
86			static int
87			ambnorm(d1, d2) /* standard order */
88			AMBSAMP d1, d2;
89			{
90			register int c;
91
92			if (c = d1->t - d2->t)
93			return(c);
94			return(d1->p - d2->p);
95			}
96
97
98	greg	2.9	int
99	greg	1.1	divsample(dp, h, r) /* sample a division */
100			register AMBSAMP *dp;
101			AMBHEMI *h;
102			RAY *r;
103			{
104			RAY ar;
105	greg	1.11	int hlist[3];
106			double spt[2];
107	greg	1.1	double xd, yd, zd;
108			double b2;
109			double phi;
110	greg	1.2	register int i;
111	greg	1.1
112	greg	1.12	if (rayorigin(&ar, r, AMBIENT, AVGREFL) < 0)
113	greg	1.4	return(-1);
114	greg	1.1	hlist[0] = r->rno;
115			hlist[1] = dp->t;
116			hlist[2] = dp->p;
117	greg	1.13	multisamp(spt, 2, urand(ilhash(hlist,3)+dp->n));
118	greg	1.11	zd = sqrt((dp->t + spt[0])/h->nt);
119			phi = 2.0PI (dp->p + spt[1])/h->np;
120	gwlarson	2.8	xd = tcos(phi) * zd;
121			yd = tsin(phi) * zd;
122	greg	1.1	zd = sqrt(1.0 - zd*zd);
123	greg	1.2	for (i = 0; i < 3; i++)
124			ar.rdir[i] = xd*h->ux[i] +
125			yd*h->uy[i] +
126			zd*h->uz[i];
127			dimlist[ndims++] = dp->t*h->np + dp->p + 90171;
128	greg	1.1	rayvalue(&ar);
129			ndims--;
130			addcolor(dp->v, ar.rcol);
131	greg	2.9	/* use rt to improve gradient calc */
132			if (ar.rt > FTINY && ar.rt < FHUGE)
133			dp->r += 1.0/ar.rt;
134	greg	1.1	/* (re)initialize error */
135			if (dp->n++) {
136			b2 = bright(dp->v)/dp->n - bright(ar.rcol);
137			b2 = b2b2 + dp->k((dp->n-1)*(dp->n-1));
138			dp->k = b2/(dp->n*dp->n);
139			} else
140			dp->k = 0.0;
141	greg	1.4	return(0);
142	greg	1.1	}
143
144
145			double
146	greg	1.12	doambient(acol, r, wt, pg, dg) /* compute ambient component */
147	greg	1.1	COLOR acol;
148			RAY *r;
149	greg	1.12	double wt;
150	greg	1.1	FVECT pg, dg;
151			{
152			double b, d;
153			AMBHEMI hemi;
154			AMBSAMP *div;
155			AMBSAMP dnew;
156			register AMBSAMP *dp;
157			double arad;
158			int ndivs, ns;
159			register int i, j;
160			/* initialize color */
161			setcolor(acol, 0.0, 0.0, 0.0);
162			/* initialize hemisphere */
163	greg	1.12	inithemi(&hemi, r, wt);
164	greg	1.1	ndivs = hemi.nt * hemi.np;
165			if (ndivs == 0)
166			return(0.0);
167			/* set number of super-samples */
168	greg	1.12	ns = ambssamp * wt + 0.5;
169	greg	1.1	if (ns > 0 \|\| pg != NULL \|\| dg != NULL) {
170			div = (AMBSAMP )malloc(ndivssizeof(AMBSAMP));
171			if (div == NULL)
172			error(SYSTEM, "out of memory in doambient");
173			} else
174			div = NULL;
175			/* sample the divisions */
176			arad = 0.0;
177			if ((dp = div) == NULL)
178			dp = &dnew;
179			for (i = 0; i < hemi.nt; i++)
180			for (j = 0; j < hemi.np; j++) {
181			dp->t = i; dp->p = j;
182			setcolor(dp->v, 0.0, 0.0, 0.0);
183	greg	1.2	dp->r = 0.0;
184	greg	1.1	dp->n = 0;
185	greg	1.4	if (divsample(dp, &hemi, r) < 0)
186	greg	1.1	goto oopsy;
187	greg	2.6	arad += dp->r;
188	greg	1.1	if (div != NULL)
189			dp++;
190	greg	2.6	else
191	greg	1.1	addcolor(acol, dp->v);
192			}
193	greg	2.5	if (ns > 0 && arad > FTINY && ndivs/arad < minarad)
194			ns = 0; /* close enough */
195			else if (ns > 0) { /* else perform super-sampling */
196	greg	1.4	comperrs(div, &hemi); /* compute errors */
197	greg	1.1	qsort(div, ndivs, sizeof(AMBSAMP), ambcmp); /* sort divs */
198			/* super-sample */
199			for (i = ns; i > 0; i--) {
200			copystruct(&dnew, div);
201	greg	1.4	if (divsample(&dnew, &hemi, r) < 0)
202	greg	1.1	goto oopsy;
203			/* reinsert */
204			dp = div;
205			j = ndivs < i ? ndivs : i;
206			while (--j > 0 && dnew.k < dp[1].k) {
207			copystruct(dp, dp+1);
208			dp++;
209			}
210			copystruct(dp, &dnew);
211			}
212	greg	1.2	if (pg != NULL \|\| dg != NULL) /* restore order */
213	greg	1.1	qsort(div, ndivs, sizeof(AMBSAMP), ambnorm);
214			}
215			/* compute returned values */
216	greg	1.3	if (div != NULL) {
217	greg	2.6	arad = 0.0;
218	greg	1.3	for (i = ndivs, dp = div; i-- > 0; dp++) {
219			arad += dp->r;
220			if (dp->n > 1) {
221			b = 1.0/dp->n;
222			scalecolor(dp->v, b);
223			dp->r *= b;
224			dp->n = 1;
225			}
226			addcolor(acol, dp->v);
227			}
228	greg	1.5	b = bright(acol);
229	greg	1.6	if (b > FTINY) {
230	greg	1.5	b = ndivs/b;
231	greg	1.6	if (pg != NULL) {
232			posgradient(pg, div, &hemi);
233			for (i = 0; i < 3; i++)
234			pg[i] *= b;
235			}
236			if (dg != NULL) {
237			dirgradient(dg, div, &hemi);
238			for (i = 0; i < 3; i++)
239			dg[i] *= b;
240			}
241			} else {
242			if (pg != NULL)
243			for (i = 0; i < 3; i++)
244			pg[i] = 0.0;
245			if (dg != NULL)
246			for (i = 0; i < 3; i++)
247			dg[i] = 0.0;
248	greg	1.5	}
249	greg	2.9	free((void *)div);
250	greg	1.3	}
251	greg	1.1	b = 1.0/ndivs;
252			scalecolor(acol, b);
253			if (arad <= FTINY)
254	greg	1.16	arad = maxarad;
255	greg	2.3	else
256	greg	1.1	arad = (ndivs+ns)/arad;
257	greg	1.15	if (pg != NULL) { /* reduce radius if gradient large */
258			d = DOT(pg,pg);
259			if (daradarad > 1.0)
260			arad = 1.0/sqrt(d);
261			}
262	greg	1.16	if (arad < minarad) {
263	greg	1.1	arad = minarad;
264	greg	1.16	if (pg != NULL && daradarad > 1.0) { /* cap gradient */
265			d = 1.0/arad/sqrt(d);
266			for (i = 0; i < 3; i++)
267			pg[i] *= d;
268			}
269			}
270	greg	2.3	if ((arad /= sqrt(wt)) > maxarad)
271			arad = maxarad;
272			return(arad);
273	greg	1.1	oopsy:
274			if (div != NULL)
275	greg	2.9	free((void *)div);
276	greg	1.1	return(0.0);
277			}
278
279
280	greg	2.9	void
281	greg	1.12	inithemi(hp, r, wt) /* initialize sampling hemisphere */
282	greg	1.1	register AMBHEMI *hp;
283			RAY *r;
284	greg	1.12	double wt;
285	greg	1.1	{
286	greg	1.2	register int i;
287	greg	1.1	/* set number of divisions */
288	greg	1.14	if (wt < (.25*PI)/ambdiv+FTINY) {
289			hp->nt = hp->np = 0;
290			return; /* zero samples */
291			}
292	greg	1.12	hp->nt = sqrt(ambdiv * wt / PI) + 0.5;
293	greg	1.14	hp->np = PI * hp->nt + 0.5;
294	greg	1.1	/* make axes */
295			VCOPY(hp->uz, r->ron);
296			hp->uy[0] = hp->uy[1] = hp->uy[2] = 0.0;
297	greg	1.2	for (i = 0; i < 3; i++)
298			if (hp->uz[i] < 0.6 && hp->uz[i] > -0.6)
299	greg	1.1	break;
300	greg	1.2	if (i >= 3)
301	greg	1.1	error(CONSISTENCY, "bad ray direction in inithemi");
302	greg	1.2	hp->uy[i] = 1.0;
303	greg	1.3	fcross(hp->ux, hp->uy, hp->uz);
304			normalize(hp->ux);
305			fcross(hp->uy, hp->uz, hp->ux);
306	greg	1.1	}
307
308
309	greg	2.9	void
310	greg	1.1	comperrs(da, hp) /* compute initial error estimates */
311	greg	1.2	AMBSAMP da; / assumes standard ordering */
312	greg	1.1	register AMBHEMI *hp;
313			{
314			double b, b2;
315			int i, j;
316			register AMBSAMP *dp;
317			/* sum differences from neighbors */
318			dp = da;
319			for (i = 0; i < hp->nt; i++)
320			for (j = 0; j < hp->np; j++) {
321	greg	1.6	#ifdef DEBUG
322			if (dp->t != i \|\| dp->p != j)
323			error(CONSISTENCY,
324			"division order in comperrs");
325			#endif
326	greg	1.1	b = bright(dp[0].v);
327			if (i > 0) { /* from above */
328			b2 = bright(dp[-hp->np].v) - b;
329			b2 = b2 0.25;
330			dp[0].k += b2;
331			dp[-hp->np].k += b2;
332			}
333			if (j > 0) { /* from behind */
334			b2 = bright(dp[-1].v) - b;
335			b2 = b2 0.25;
336			dp[0].k += b2;
337			dp[-1].k += b2;
338	greg	1.4	} else { /* around */
339			b2 = bright(dp[hp->np-1].v) - b;
340	greg	1.1	b2 = b2 0.25;
341			dp[0].k += b2;
342	greg	1.4	dp[hp->np-1].k += b2;
343	greg	1.1	}
344			dp++;
345			}
346			/* divide by number of neighbors */
347			dp = da;
348			for (j = 0; j < hp->np; j++) /* top row */
349			(dp++)->k *= 1.0/3.0;
350			if (hp->nt < 2)
351			return;
352			for (i = 1; i < hp->nt-1; i++) /* central region */
353			for (j = 0; j < hp->np; j++)
354			(dp++)->k *= 0.25;
355			for (j = 0; j < hp->np; j++) /* bottom row */
356			(dp++)->k *= 1.0/3.0;
357			}
358
359
360	greg	2.9	void
361	greg	1.1	posgradient(gv, da, hp) /* compute position gradient */
362			FVECT gv;
363	greg	1.2	AMBSAMP da; / assumes standard ordering */
364	greg	2.2	register AMBHEMI *hp;
365	greg	1.1	{
366	greg	1.2	register int i, j;
367	greg	2.2	double nextsine, lastsine, b, d;
368	greg	1.2	double mag0, mag1;
369			double phi, cosp, sinp, xd, yd;
370			register AMBSAMP *dp;
371
372			xd = yd = 0.0;
373			for (j = 0; j < hp->np; j++) {
374			dp = da + j;
375			mag0 = mag1 = 0.0;
376	greg	2.2	lastsine = 0.0;
377	greg	1.2	for (i = 0; i < hp->nt; i++) {
378			#ifdef DEBUG
379			if (dp->t != i \|\| dp->p != j)
380			error(CONSISTENCY,
381			"division order in posgradient");
382			#endif
383			b = bright(dp->v);
384			if (i > 0) {
385			d = dp[-hp->np].r;
386			if (dp[0].r > d) d = dp[0].r;
387	greg	2.2	/* sin(t)cos(t)^2 /
388			d = lastsine (1.0 - (double)i/hp->nt);
389	greg	1.2	mag0 += d*(b - bright(dp[-hp->np].v));
390			}
391	greg	2.2	nextsine = sqrt((double)(i+1)/hp->nt);
392	greg	1.2	if (j > 0) {
393			d = dp[-1].r;
394			if (dp[0].r > d) d = dp[0].r;
395	greg	2.2	mag1 += d * (nextsine - lastsine) *
396			(b - bright(dp[-1].v));
397	greg	1.2	} else {
398			d = dp[hp->np-1].r;
399			if (dp[0].r > d) d = dp[0].r;
400	greg	2.2	mag1 += d * (nextsine - lastsine) *
401			(b - bright(dp[hp->np-1].v));
402	greg	1.2	}
403			dp += hp->np;
404	greg	2.2	lastsine = nextsine;
405	greg	1.2	}
406	greg	2.2	mag0 = 2.0PI / hp->np;
407	greg	1.2	phi = 2.0PI (double)j/hp->np;
408	gwlarson	2.8	cosp = tcos(phi); sinp = tsin(phi);
409	greg	1.2	xd += mag0cosp - mag1sinp;
410			yd += mag0sinp + mag1cosp;
411			}
412			for (i = 0; i < 3; i++)
413	greg	1.5	gv[i] = (xdhp->ux[i] + ydhp->uy[i])/PI;
414	greg	1.1	}
415
416
417	greg	2.9	void
418	greg	1.1	dirgradient(gv, da, hp) /* compute direction gradient */
419			FVECT gv;
420	greg	1.2	AMBSAMP da; / assumes standard ordering */
421	greg	2.2	register AMBHEMI *hp;
422	greg	1.1	{
423	greg	1.2	register int i, j;
424			double mag;
425			double phi, xd, yd;
426			register AMBSAMP *dp;
427
428			xd = yd = 0.0;
429			for (j = 0; j < hp->np; j++) {
430			dp = da + j;
431			mag = 0.0;
432			for (i = 0; i < hp->nt; i++) {
433			#ifdef DEBUG
434			if (dp->t != i \|\| dp->p != j)
435			error(CONSISTENCY,
436			"division order in dirgradient");
437			#endif
438	greg	2.2	/* tan(t) */
439			mag += bright(dp->v)/sqrt(hp->nt/(i+.5) - 1.0);
440	greg	1.2	dp += hp->np;
441			}
442			phi = 2.0PI (j+.5)/hp->np + PI/2.0;
443	gwlarson	2.8	xd += mag * tcos(phi);
444			yd += mag * tsin(phi);
445	greg	1.2	}
446			for (i = 0; i < 3; i++)
447	greg	2.2	gv[i] = (xdhp->ux[i] + ydhp->uy[i])/(hp->nt*hp->np);
448	greg	1.1	}