src/rt/ambcomp.c

#ifndef lint
static const char       RCSid[] = "$Id: ambcomp.c,v 2.22 2010/09/26 15:51:15 greg Exp $";
#endif
/*
 * Routines to compute "ambient" values using Monte Carlo
 *
 *  Declarations of external symbols in ambient.h
 */

#include "copyright.h"

#include  "ray.h"

#include  "ambient.h"

#include  "random.h"


void
inithemi(                       /* initialize sampling hemisphere */
        AMBHEMI  *hp,
        COLOR ac,
        RAY  *r,
        double  wt
)
{
        double  d;
        int  i;
                                        /* set number of divisions */
        if (ambacc <= FTINY &&
                        wt > (d = 0.8*intens(ac)*r->rweight/(ambdiv*minweight)))
                wt = d;                 /* avoid ray termination */
        hp->nt = sqrt(ambdiv * wt / PI) + 0.5;
        i = ambacc > FTINY ? 3 : 1;     /* minimum number of samples */
        if (hp->nt < i)
                hp->nt = i;
        hp->np = PI * hp->nt + 0.5;
                                        /* set number of super-samples */
        hp->ns = ambssamp * wt + 0.5;
                                        /* assign coefficient */
        copycolor(hp->acoef, ac);
        d = 1.0/(hp->nt*hp->np);
        scalecolor(hp->acoef, d);
                                        /* 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);
}


int
divsample(                              /* sample a division */
        AMBSAMP  *dp,
        AMBHEMI  *h,
        RAY  *r
)
{
        RAY  ar;
        int  hlist[3];
        double  spt[2];
        double  xd, yd, zd;
        double  b2;
        double  phi;
        int  i;
                                        /* ambient coefficient for weight */
        if (ambacc > FTINY)
                setcolor(ar.rcoef, AVGREFL, AVGREFL, AVGREFL);
        else
                copycolor(ar.rcoef, h->acoef);
        if (rayorigin(&ar, AMBIENT, r, ar.rcoef) < 0)
                return(-1);
        if (ambacc > FTINY) {
                multcolor(ar.rcoef, h->acoef);
                scalecolor(ar.rcoef, 1./AVGREFL);
        }
        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];
        checknorm(ar.rdir);
        dimlist[ndims++] = dp->t*h->np + dp->p + 90171;
        rayvalue(&ar);
        ndims--;
        multcolor(ar.rcol, ar.rcoef);   /* apply coefficient */
        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);
}


static int
ambcmp(                                 /* decreasing order */
        const void *p1,
        const void *p2
)
{
        const AMBSAMP   *d1 = (const AMBSAMP *)p1;
        const AMBSAMP   *d2 = (const AMBSAMP *)p2;

        if (d1->k < d2->k)
                return(1);
        if (d1->k > d2->k)
                return(-1);
        return(0);
}


static int
ambnorm(                                /* standard order */
        const void *p1,
        const void *p2
)
{
        const AMBSAMP   *d1 = (const AMBSAMP *)p1;
        const AMBSAMP   *d2 = (const AMBSAMP *)p2;
        int     c;

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


double
doambient(                              /* compute ambient component */
        COLOR  rcol,
        RAY  *r,
        double  wt,
        FVECT  pg,
        FVECT  dg
)
{
        double  b, d;
        AMBHEMI  hemi;
        AMBSAMP  *div;
        AMBSAMP  dnew;
        double  acol[3];
        AMBSAMP  *dp;
        double  arad;
        int  divcnt;
        int  i, j;
                                        /* initialize hemisphere */
        inithemi(&hemi, rcol, r, wt);
        divcnt = hemi.nt * hemi.np;
                                        /* initialize */
        if (pg != NULL)
                pg[0] = pg[1] = pg[2] = 0.0;
        if (dg != NULL)
                dg[0] = dg[1] = dg[2] = 0.0;
        setcolor(rcol, 0.0, 0.0, 0.0);
        if (divcnt == 0)
                return(0.0);
                                        /* allocate super-samples */
        if (hemi.ns > 0 || pg != NULL || dg != NULL) {
                div = (AMBSAMP *)malloc(divcnt*sizeof(AMBSAMP));
                if (div == NULL)
                        error(SYSTEM, "out of memory in doambient");
        } else
                div = NULL;
                                        /* sample the divisions */
        arad = 0.0;
        acol[0] = acol[1] = acol[2] = 0.0;
        if ((dp = div) == NULL)
                dp = &dnew;
        divcnt = 0;
        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) {
                                if (div != NULL)
                                        dp++;
                                continue;
                        }
                        arad += dp->r;
                        divcnt++;
                        if (div != NULL)
                                dp++;
                        else
                                addcolor(acol, dp->v);
                }
        if (!divcnt) {
                if (div != NULL)
                        free((void *)div);
                return(0.0);            /* no samples taken */
        }
        if (divcnt < hemi.nt*hemi.np) {
                pg = dg = NULL;         /* incomplete sampling */
                hemi.ns = 0;
        } else if (arad > FTINY && divcnt/arad < minarad) {
                hemi.ns = 0;            /* close enough */
        } else if (hemi.ns > 0) {       /* else perform super-sampling? */
                comperrs(div, &hemi);                   /* compute errors */
                qsort(div, divcnt, sizeof(AMBSAMP), ambcmp);    /* sort divs */
                                                /* super-sample */
                for (i = hemi.ns; i > 0; i--) {
                        dnew = *div;
                        if (divsample(&dnew, &hemi, r) < 0) {
                                dp++;
                                continue;
                        }
                        dp = div;               /* reinsert */
                        j = divcnt < i ? divcnt : i;
                        while (--j > 0 && dnew.k < dp[1].k) {
                                *dp = *(dp+1);
                                dp++;
                        }
                        *dp = dnew;
                }
                if (pg != NULL || dg != NULL)   /* restore order */
                        qsort(div, divcnt, sizeof(AMBSAMP), ambnorm);
        }
                                        /* compute returned values */
        if (div != NULL) {
                arad = 0.0;             /* note: divcnt may be < nt*np */
                for (i = hemi.nt*hemi.np, 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 = 1.0/b;      /* compute & normalize gradient(s) */
                        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;
                        }
                }
                free((void *)div);
        }
        copycolor(rcol, acol);
        if (arad <= FTINY)
                arad = maxarad;
        else
                arad = (divcnt+hemi.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);
}


void
comperrs(                       /* compute initial error estimates */
        AMBSAMP  *da,   /* assumes standard ordering */
        AMBHEMI  *hp
)
{
        double  b, b2;
        int  i, j;
        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(                                    /* compute position gradient */
        FVECT  gv,
        AMBSAMP  *da,                   /* assumes standard ordering */
        AMBHEMI  *hp
)
{
        int  i, j;
        double  nextsine, lastsine, b, d;
        double  mag0, mag1;
        double  phi, cosp, sinp, xd, yd;
        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])*(hp->nt*hp->np)/PI;
}


void
dirgradient(                                    /* compute direction gradient */
        FVECT  gv,
        AMBSAMP  *da,                   /* assumes standard ordering */
        AMBHEMI  *hp
)
{
        int  i, j;
        double  mag;
        double  phi, xd, yd;
        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];
}
Revision:	2.23
Committed:	Tue Feb 5 05:40:06 2013 UTC (11 years, 2 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.22:	+22 -19 lines
Log Message:	Improved accuracy of ambient calculation for large -ad settings
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.23	static const char RCSid[] = "$Id: ambcomp.c,v 2.22 2010/09/26 15:51:15 greg Exp $";
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	greg	2.10	#include "copyright.h"
11	greg	1.1
12			#include "ray.h"
13
14			#include "ambient.h"
15
16			#include "random.h"
17
18
19	greg	2.15	void
20	greg	2.14	inithemi( /* initialize sampling hemisphere */
21	greg	2.23	AMBHEMI *hp,
22	greg	2.16	COLOR ac,
23	greg	2.14	RAY *r,
24			double wt
25			)
26	greg	1.1	{
27	greg	2.16	double d;
28	greg	2.23	int i;
29	greg	2.14	/* set number of divisions */
30	greg	2.16	if (ambacc <= FTINY &&
31	greg	2.20	wt > (d = 0.8intens(ac)r->rweight/(ambdiv*minweight)))
32	greg	2.16	wt = d; /* avoid ray termination */
33			hp->nt = sqrt(ambdiv * wt / PI) + 0.5;
34	greg	2.14	i = ambacc > FTINY ? 3 : 1; /* minimum number of samples */
35			if (hp->nt < i)
36			hp->nt = i;
37			hp->np = PI * hp->nt + 0.5;
38			/* set number of super-samples */
39	greg	2.15	hp->ns = ambssamp * wt + 0.5;
40	greg	2.16	/* assign coefficient */
41	greg	2.14	copycolor(hp->acoef, ac);
42	greg	2.16	d = 1.0/(hp->nt*hp->np);
43			scalecolor(hp->acoef, d);
44	greg	2.14	/* make axes */
45			VCOPY(hp->uz, r->ron);
46			hp->uy[0] = hp->uy[1] = hp->uy[2] = 0.0;
47			for (i = 0; i < 3; i++)
48			if (hp->uz[i] < 0.6 && hp->uz[i] > -0.6)
49			break;
50			if (i >= 3)
51			error(CONSISTENCY, "bad ray direction in inithemi");
52			hp->uy[i] = 1.0;
53			fcross(hp->ux, hp->uy, hp->uz);
54			normalize(hp->ux);
55			fcross(hp->uy, hp->uz, hp->ux);
56	greg	1.1	}
57
58
59	greg	2.9	int
60	greg	2.14	divsample( /* sample a division */
61	greg	2.23	AMBSAMP *dp,
62	greg	2.14	AMBHEMI *h,
63			RAY *r
64			)
65	greg	1.1	{
66			RAY ar;
67	greg	1.11	int hlist[3];
68			double spt[2];
69	greg	1.1	double xd, yd, zd;
70			double b2;
71			double phi;
72	greg	2.23	int i;
73	greg	2.15	/* ambient coefficient for weight */
74	greg	2.16	if (ambacc > FTINY)
75			setcolor(ar.rcoef, AVGREFL, AVGREFL, AVGREFL);
76			else
77			copycolor(ar.rcoef, h->acoef);
78	greg	2.14	if (rayorigin(&ar, AMBIENT, r, ar.rcoef) < 0)
79	greg	1.4	return(-1);
80	greg	2.17	if (ambacc > FTINY) {
81			multcolor(ar.rcoef, h->acoef);
82			scalecolor(ar.rcoef, 1./AVGREFL);
83			}
84	greg	1.1	hlist[0] = r->rno;
85			hlist[1] = dp->t;
86			hlist[2] = dp->p;
87	greg	1.13	multisamp(spt, 2, urand(ilhash(hlist,3)+dp->n));
88	greg	1.11	zd = sqrt((dp->t + spt[0])/h->nt);
89			phi = 2.0PI (dp->p + spt[1])/h->np;
90	gwlarson	2.8	xd = tcos(phi) * zd;
91			yd = tsin(phi) * zd;
92	greg	1.1	zd = sqrt(1.0 - zd*zd);
93	greg	1.2	for (i = 0; i < 3; i++)
94			ar.rdir[i] = xd*h->ux[i] +
95			yd*h->uy[i] +
96			zd*h->uz[i];
97	greg	2.22	checknorm(ar.rdir);
98	greg	1.2	dimlist[ndims++] = dp->t*h->np + dp->p + 90171;
99	greg	1.1	rayvalue(&ar);
100			ndims--;
101	greg	2.16	multcolor(ar.rcol, ar.rcoef); /* apply coefficient */
102	greg	1.1	addcolor(dp->v, ar.rcol);
103	greg	2.9	/* use rt to improve gradient calc */
104			if (ar.rt > FTINY && ar.rt < FHUGE)
105			dp->r += 1.0/ar.rt;
106	greg	1.1	/* (re)initialize error */
107			if (dp->n++) {
108			b2 = bright(dp->v)/dp->n - bright(ar.rcol);
109			b2 = b2b2 + dp->k((dp->n-1)*(dp->n-1));
110			dp->k = b2/(dp->n*dp->n);
111			} else
112			dp->k = 0.0;
113	greg	1.4	return(0);
114	greg	1.1	}
115
116
117	greg	2.14	static int
118			ambcmp( /* decreasing order */
119			const void *p1,
120			const void *p2
121			)
122			{
123			const AMBSAMP d1 = (const AMBSAMP )p1;
124			const AMBSAMP d2 = (const AMBSAMP )p2;
125
126			if (d1->k < d2->k)
127			return(1);
128			if (d1->k > d2->k)
129			return(-1);
130			return(0);
131			}
132
133
134			static int
135			ambnorm( /* standard order */
136			const void *p1,
137			const void *p2
138			)
139			{
140			const AMBSAMP d1 = (const AMBSAMP )p1;
141			const AMBSAMP d2 = (const AMBSAMP )p2;
142	greg	2.23	int c;
143	greg	2.14
144			if ( (c = d1->t - d2->t) )
145			return(c);
146			return(d1->p - d2->p);
147			}
148
149
150	greg	1.1	double
151	greg	2.14	doambient( /* compute ambient component */
152	greg	2.23	COLOR rcol,
153	greg	2.14	RAY *r,
154			double wt,
155			FVECT pg,
156			FVECT dg
157			)
158	greg	1.1	{
159			double b, d;
160			AMBHEMI hemi;
161			AMBSAMP *div;
162			AMBSAMP dnew;
163	greg	2.23	double acol[3];
164			AMBSAMP *dp;
165	greg	1.1	double arad;
166	greg	2.19	int divcnt;
167	greg	2.23	int i, j;
168	greg	1.1	/* initialize hemisphere */
169	greg	2.23	inithemi(&hemi, rcol, r, wt);
170	greg	2.19	divcnt = hemi.nt * hemi.np;
171	greg	2.17	/* initialize */
172			if (pg != NULL)
173			pg[0] = pg[1] = pg[2] = 0.0;
174			if (dg != NULL)
175			dg[0] = dg[1] = dg[2] = 0.0;
176	greg	2.23	setcolor(rcol, 0.0, 0.0, 0.0);
177	greg	2.19	if (divcnt == 0)
178	greg	1.1	return(0.0);
179	greg	2.14	/* allocate super-samples */
180	greg	2.15	if (hemi.ns > 0 \|\| pg != NULL \|\| dg != NULL) {
181	greg	2.19	div = (AMBSAMP )malloc(divcntsizeof(AMBSAMP));
182	greg	1.1	if (div == NULL)
183			error(SYSTEM, "out of memory in doambient");
184			} else
185			div = NULL;
186			/* sample the divisions */
187			arad = 0.0;
188	greg	2.23	acol[0] = acol[1] = acol[2] = 0.0;
189	greg	1.1	if ((dp = div) == NULL)
190			dp = &dnew;
191	greg	2.19	divcnt = 0;
192	greg	1.1	for (i = 0; i < hemi.nt; i++)
193			for (j = 0; j < hemi.np; j++) {
194			dp->t = i; dp->p = j;
195			setcolor(dp->v, 0.0, 0.0, 0.0);
196	greg	1.2	dp->r = 0.0;
197	greg	1.1	dp->n = 0;
198	greg	2.16	if (divsample(dp, &hemi, r) < 0) {
199	greg	2.19	if (div != NULL)
200			dp++;
201	greg	2.16	continue;
202			}
203	greg	2.6	arad += dp->r;
204	greg	2.19	divcnt++;
205	greg	1.1	if (div != NULL)
206			dp++;
207	greg	2.6	else
208	greg	1.1	addcolor(acol, dp->v);
209			}
210	greg	2.21	if (!divcnt) {
211			if (div != NULL)
212			free((void *)div);
213	greg	2.19	return(0.0); /* no samples taken */
214	greg	2.21	}
215	greg	2.19	if (divcnt < hemi.nt*hemi.np) {
216			pg = dg = NULL; /* incomplete sampling */
217			hemi.ns = 0;
218			} else if (arad > FTINY && divcnt/arad < minarad) {
219	greg	2.15	hemi.ns = 0; /* close enough */
220	greg	2.19	} else if (hemi.ns > 0) { /* else perform super-sampling? */
221	greg	1.4	comperrs(div, &hemi); /* compute errors */
222	greg	2.19	qsort(div, divcnt, sizeof(AMBSAMP), ambcmp); /* sort divs */
223	greg	1.1	/* super-sample */
224	greg	2.15	for (i = hemi.ns; i > 0; i--) {
225	schorsch	2.11	dnew = *div;
226	greg	2.16	if (divsample(&dnew, &hemi, r) < 0) {
227			dp++;
228			continue;
229			}
230			dp = div; /* reinsert */
231	greg	2.19	j = divcnt < i ? divcnt : i;
232	greg	1.1	while (--j > 0 && dnew.k < dp[1].k) {
233	schorsch	2.11	dp = (dp+1);
234	greg	1.1	dp++;
235			}
236	schorsch	2.11	*dp = dnew;
237	greg	1.1	}
238	greg	1.2	if (pg != NULL \|\| dg != NULL) /* restore order */
239	greg	2.19	qsort(div, divcnt, sizeof(AMBSAMP), ambnorm);
240	greg	1.1	}
241			/* compute returned values */
242	greg	1.3	if (div != NULL) {
243	greg	2.19	arad = 0.0; /* note: divcnt may be < ntnp /
244			for (i = hemi.nt*hemi.np, dp = div; i-- > 0; dp++) {
245	greg	1.3	arad += dp->r;
246			if (dp->n > 1) {
247			b = 1.0/dp->n;
248			scalecolor(dp->v, b);
249			dp->r *= b;
250			dp->n = 1;
251			}
252			addcolor(acol, dp->v);
253			}
254	greg	1.5	b = bright(acol);
255	greg	1.6	if (b > FTINY) {
256	greg	2.17	b = 1.0/b; /* compute & normalize gradient(s) */
257	greg	1.6	if (pg != NULL) {
258			posgradient(pg, div, &hemi);
259			for (i = 0; i < 3; i++)
260			pg[i] *= b;
261			}
262			if (dg != NULL) {
263			dirgradient(dg, div, &hemi);
264			for (i = 0; i < 3; i++)
265			dg[i] *= b;
266			}
267	greg	1.5	}
268	greg	2.9	free((void *)div);
269	greg	1.3	}
270	greg	2.23	copycolor(rcol, acol);
271	greg	1.1	if (arad <= FTINY)
272	greg	1.16	arad = maxarad;
273	greg	2.3	else
274	greg	2.19	arad = (divcnt+hemi.ns)/arad;
275	greg	1.15	if (pg != NULL) { /* reduce radius if gradient large */
276			d = DOT(pg,pg);
277			if (daradarad > 1.0)
278			arad = 1.0/sqrt(d);
279			}
280	greg	1.16	if (arad < minarad) {
281	greg	1.1	arad = minarad;
282	greg	1.16	if (pg != NULL && daradarad > 1.0) { /* cap gradient */
283			d = 1.0/arad/sqrt(d);
284			for (i = 0; i < 3; i++)
285			pg[i] *= d;
286			}
287			}
288	greg	2.3	if ((arad /= sqrt(wt)) > maxarad)
289			arad = maxarad;
290			return(arad);
291	greg	1.1	}
292
293
294	greg	2.9	void
295	greg	2.14	comperrs( /* compute initial error estimates */
296			AMBSAMP da, / assumes standard ordering */
297	greg	2.23	AMBHEMI *hp
298	greg	2.14	)
299	greg	1.1	{
300			double b, b2;
301			int i, j;
302	greg	2.23	AMBSAMP *dp;
303	greg	1.1	/* sum differences from neighbors */
304			dp = da;
305			for (i = 0; i < hp->nt; i++)
306			for (j = 0; j < hp->np; j++) {
307	greg	1.6	#ifdef DEBUG
308			if (dp->t != i \|\| dp->p != j)
309			error(CONSISTENCY,
310			"division order in comperrs");
311			#endif
312	greg	1.1	b = bright(dp[0].v);
313			if (i > 0) { /* from above */
314			b2 = bright(dp[-hp->np].v) - b;
315			b2 = b2 0.25;
316			dp[0].k += b2;
317			dp[-hp->np].k += b2;
318			}
319			if (j > 0) { /* from behind */
320			b2 = bright(dp[-1].v) - b;
321			b2 = b2 0.25;
322			dp[0].k += b2;
323			dp[-1].k += b2;
324	greg	1.4	} else { /* around */
325			b2 = bright(dp[hp->np-1].v) - b;
326	greg	1.1	b2 = b2 0.25;
327			dp[0].k += b2;
328	greg	1.4	dp[hp->np-1].k += b2;
329	greg	1.1	}
330			dp++;
331			}
332			/* divide by number of neighbors */
333			dp = da;
334			for (j = 0; j < hp->np; j++) /* top row */
335			(dp++)->k *= 1.0/3.0;
336			if (hp->nt < 2)
337			return;
338			for (i = 1; i < hp->nt-1; i++) /* central region */
339			for (j = 0; j < hp->np; j++)
340			(dp++)->k *= 0.25;
341			for (j = 0; j < hp->np; j++) /* bottom row */
342			(dp++)->k *= 1.0/3.0;
343			}
344
345
346	greg	2.9	void
347	greg	2.14	posgradient( /* compute position gradient */
348			FVECT gv,
349			AMBSAMP da, / assumes standard ordering */
350	greg	2.23	AMBHEMI *hp
351	greg	2.14	)
352	greg	1.1	{
353	greg	2.23	int i, j;
354	greg	2.2	double nextsine, lastsine, b, d;
355	greg	1.2	double mag0, mag1;
356			double phi, cosp, sinp, xd, yd;
357	greg	2.23	AMBSAMP *dp;
358	greg	1.2
359			xd = yd = 0.0;
360			for (j = 0; j < hp->np; j++) {
361			dp = da + j;
362			mag0 = mag1 = 0.0;
363	greg	2.2	lastsine = 0.0;
364	greg	1.2	for (i = 0; i < hp->nt; i++) {
365			#ifdef DEBUG
366			if (dp->t != i \|\| dp->p != j)
367			error(CONSISTENCY,
368			"division order in posgradient");
369			#endif
370			b = bright(dp->v);
371			if (i > 0) {
372			d = dp[-hp->np].r;
373			if (dp[0].r > d) d = dp[0].r;
374	greg	2.2	/* sin(t)cos(t)^2 /
375			d = lastsine (1.0 - (double)i/hp->nt);
376	greg	1.2	mag0 += d*(b - bright(dp[-hp->np].v));
377			}
378	greg	2.2	nextsine = sqrt((double)(i+1)/hp->nt);
379	greg	1.2	if (j > 0) {
380			d = dp[-1].r;
381			if (dp[0].r > d) d = dp[0].r;
382	greg	2.2	mag1 += d * (nextsine - lastsine) *
383			(b - bright(dp[-1].v));
384	greg	1.2	} else {
385			d = dp[hp->np-1].r;
386			if (dp[0].r > d) d = dp[0].r;
387	greg	2.2	mag1 += d * (nextsine - lastsine) *
388			(b - bright(dp[hp->np-1].v));
389	greg	1.2	}
390			dp += hp->np;
391	greg	2.2	lastsine = nextsine;
392	greg	1.2	}
393	greg	2.2	mag0 = 2.0PI / hp->np;
394	greg	1.2	phi = 2.0PI (double)j/hp->np;
395	gwlarson	2.8	cosp = tcos(phi); sinp = tsin(phi);
396	greg	1.2	xd += mag0cosp - mag1sinp;
397			yd += mag0sinp + mag1cosp;
398			}
399			for (i = 0; i < 3; i++)
400	greg	2.16	gv[i] = (xdhp->ux[i] + ydhp->uy[i])(hp->nthp->np)/PI;
401	greg	1.1	}
402
403
404	greg	2.9	void
405	greg	2.14	dirgradient( /* compute direction gradient */
406			FVECT gv,
407			AMBSAMP da, / assumes standard ordering */
408	greg	2.23	AMBHEMI *hp
409	greg	2.14	)
410	greg	1.1	{
411	greg	2.23	int i, j;
412	greg	1.2	double mag;
413			double phi, xd, yd;
414	greg	2.23	AMBSAMP *dp;
415	greg	1.2
416			xd = yd = 0.0;
417			for (j = 0; j < hp->np; j++) {
418			dp = da + j;
419			mag = 0.0;
420			for (i = 0; i < hp->nt; i++) {
421			#ifdef DEBUG
422			if (dp->t != i \|\| dp->p != j)
423			error(CONSISTENCY,
424			"division order in dirgradient");
425			#endif
426	greg	2.2	/* tan(t) */
427			mag += bright(dp->v)/sqrt(hp->nt/(i+.5) - 1.0);
428	greg	1.2	dp += hp->np;
429			}
430			phi = 2.0PI (j+.5)/hp->np + PI/2.0;
431	gwlarson	2.8	xd += mag * tcos(phi);
432			yd += mag * tsin(phi);
433	greg	1.2	}
434			for (i = 0; i < 3; i++)
435	greg	2.16	gv[i] = xdhp->ux[i] + ydhp->uy[i];
436	greg	1.1	}