src/rt/ambcomp.c

#ifndef lint
static const char       RCSid[] = "$Id: ambcomp.c,v 2.14 2005/04/19 01:15:06 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 */
        register AMBHEMI  *hp,
        RAY  *r,
        COLOR ac, 
        double  wt
)
{
        register int  i;
                                        /* set number of divisions */
        hp->nt = sqrt(ambdiv * wt * (1./PI/AVGREFL)) + 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 coefficients */
        copycolor(hp->acoef, ac);
        if (wt >= r->rweight)
                hp->drc = 1.;
        else
                hp->drc = wt / r->rweight;
                                        /* 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 */
        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;
                                        /* ambient coefficient for weight */
        setcolor(ar.rcoef, h->drc, h->drc, h->drc);
        if (rayorigin(&ar, AMBIENT, r, ar.rcoef) < 0)
                return(-1);
        copycolor(ar.rcoef, h->acoef);  /* correct coefficient for trace */
        b2 = 1.0/(h->nt*h->np + h->ns); /* XXX not uniform if ns > 0 */
        scalecolor(ar.rcoef, b2);
        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);
}


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;
        register int    c;

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


double
doambient(                              /* compute ambient component */
        COLOR  acol,
        RAY  *r,
        COLOR  ac,
        double  wt,
        FVECT  pg,
        FVECT  dg
)
{
        double  b, d;
        AMBHEMI  hemi;
        AMBSAMP  *div;
        AMBSAMP  dnew;
        register AMBSAMP  *dp;
        double  arad;
        int  ndivs;
        register int  i, j;
                                        /* initialize color */
        setcolor(acol, 0.0, 0.0, 0.0);
                                        /* initialize hemisphere */
        inithemi(&hemi, r, ac, wt);
        ndivs = hemi.nt * hemi.np;
        if (ndivs == 0)
                return(0.0);
                                        /* allocate super-samples */
        if (hemi.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 (hemi.ns > 0 && arad > FTINY && ndivs/arad < minarad)
                hemi.ns = 0;            /* close enough */
        else if (hemi.ns > 0) {         /* else perform super-sampling */
                comperrs(div, &hemi);                   /* compute errors */
                qsort(div, ndivs, sizeof(AMBSAMP), ambcmp);     /* sort divs */
                                                /* super-sample */
                for (i = hemi.ns; i > 0; i--) {
                        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) {
                                *dp = *(dp+1);
                                dp++;
                        }
                        *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+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);
oopsy:
        if (div != NULL)
                free((void *)div);
        return(0.0);
}


void
comperrs(                       /* 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(                                    /* 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(                                    /* 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:	2.15
Committed:	Sat May 28 22:27:54 2005 UTC (18 years, 11 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.14:	+22 -24 lines
Log Message:	Fixed application of ray weights and coefficients in ambient calculation
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.15	static const char RCSid[] = "$Id: ambcomp.c,v 2.14 2005/04/19 01:15:06 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			register AMBHEMI *hp,
22			RAY *r,
23			COLOR ac,
24			double wt
25			)
26	greg	1.1	{
27	greg	2.14	register int i;
28			/* set number of divisions */
29	greg	2.15	hp->nt = sqrt(ambdiv * wt * (1./PI/AVGREFL)) + 0.5;
30	greg	2.14	i = ambacc > FTINY ? 3 : 1; /* minimum number of samples */
31			if (hp->nt < i)
32			hp->nt = i;
33			hp->np = PI * hp->nt + 0.5;
34			/* set number of super-samples */
35	greg	2.15	hp->ns = ambssamp * wt + 0.5;
36			/* assign coefficients */
37	greg	2.14	copycolor(hp->acoef, ac);
38	greg	2.15	if (wt >= r->rweight)
39			hp->drc = 1.;
40			else
41			hp->drc = wt / r->rweight;
42	greg	2.14	/* make axes */
43			VCOPY(hp->uz, r->ron);
44			hp->uy[0] = hp->uy[1] = hp->uy[2] = 0.0;
45			for (i = 0; i < 3; i++)
46			if (hp->uz[i] < 0.6 && hp->uz[i] > -0.6)
47			break;
48			if (i >= 3)
49			error(CONSISTENCY, "bad ray direction in inithemi");
50			hp->uy[i] = 1.0;
51			fcross(hp->ux, hp->uy, hp->uz);
52			normalize(hp->ux);
53			fcross(hp->uy, hp->uz, hp->ux);
54	greg	1.1	}
55
56
57	greg	2.9	int
58	greg	2.14	divsample( /* sample a division */
59			register AMBSAMP *dp,
60			AMBHEMI *h,
61			RAY *r
62			)
63	greg	1.1	{
64			RAY ar;
65	greg	1.11	int hlist[3];
66			double spt[2];
67	greg	1.1	double xd, yd, zd;
68			double b2;
69			double phi;
70	greg	1.2	register int i;
71	greg	2.15	/* ambient coefficient for weight */
72			setcolor(ar.rcoef, h->drc, h->drc, h->drc);
73	greg	2.14	if (rayorigin(&ar, AMBIENT, r, ar.rcoef) < 0)
74	greg	1.4	return(-1);
75	greg	2.15	copycolor(ar.rcoef, h->acoef); /* correct coefficient for trace */
76			b2 = 1.0/(h->nth->np + h->ns); / XXX not uniform if ns > 0 */
77			scalecolor(ar.rcoef, b2);
78	greg	1.1	hlist[0] = r->rno;
79			hlist[1] = dp->t;
80			hlist[2] = dp->p;
81	greg	1.13	multisamp(spt, 2, urand(ilhash(hlist,3)+dp->n));
82	greg	1.11	zd = sqrt((dp->t + spt[0])/h->nt);
83			phi = 2.0PI (dp->p + spt[1])/h->np;
84	gwlarson	2.8	xd = tcos(phi) * zd;
85			yd = tsin(phi) * zd;
86	greg	1.1	zd = sqrt(1.0 - zd*zd);
87	greg	1.2	for (i = 0; i < 3; i++)
88			ar.rdir[i] = xd*h->ux[i] +
89			yd*h->uy[i] +
90			zd*h->uz[i];
91			dimlist[ndims++] = dp->t*h->np + dp->p + 90171;
92	greg	1.1	rayvalue(&ar);
93			ndims--;
94			addcolor(dp->v, ar.rcol);
95	greg	2.9	/* use rt to improve gradient calc */
96			if (ar.rt > FTINY && ar.rt < FHUGE)
97			dp->r += 1.0/ar.rt;
98	greg	1.1	/* (re)initialize error */
99			if (dp->n++) {
100			b2 = bright(dp->v)/dp->n - bright(ar.rcol);
101			b2 = b2b2 + dp->k((dp->n-1)*(dp->n-1));
102			dp->k = b2/(dp->n*dp->n);
103			} else
104			dp->k = 0.0;
105	greg	1.4	return(0);
106	greg	1.1	}
107
108
109	greg	2.14	static int
110			ambcmp( /* decreasing order */
111			const void *p1,
112			const void *p2
113			)
114			{
115			const AMBSAMP d1 = (const AMBSAMP )p1;
116			const AMBSAMP d2 = (const AMBSAMP )p2;
117
118			if (d1->k < d2->k)
119			return(1);
120			if (d1->k > d2->k)
121			return(-1);
122			return(0);
123			}
124
125
126			static int
127			ambnorm( /* standard order */
128			const void *p1,
129			const void *p2
130			)
131			{
132			const AMBSAMP d1 = (const AMBSAMP )p1;
133			const AMBSAMP d2 = (const AMBSAMP )p2;
134			register int c;
135
136			if ( (c = d1->t - d2->t) )
137			return(c);
138			return(d1->p - d2->p);
139			}
140
141
142	greg	1.1	double
143	greg	2.14	doambient( /* compute ambient component */
144			COLOR acol,
145			RAY *r,
146			COLOR ac,
147			double wt,
148			FVECT pg,
149			FVECT dg
150			)
151	greg	1.1	{
152			double b, d;
153			AMBHEMI hemi;
154			AMBSAMP *div;
155			AMBSAMP dnew;
156			register AMBSAMP *dp;
157			double arad;
158	greg	2.15	int ndivs;
159	greg	1.1	register int i, j;
160			/* initialize color */
161			setcolor(acol, 0.0, 0.0, 0.0);
162			/* initialize hemisphere */
163	greg	2.15	inithemi(&hemi, r, ac, wt);
164	greg	1.1	ndivs = hemi.nt * hemi.np;
165			if (ndivs == 0)
166			return(0.0);
167	greg	2.14	/* allocate super-samples */
168	greg	2.15	if (hemi.ns > 0 \|\| pg != NULL \|\| dg != NULL) {
169	greg	1.1	div = (AMBSAMP )malloc(ndivssizeof(AMBSAMP));
170			if (div == NULL)
171			error(SYSTEM, "out of memory in doambient");
172			} else
173			div = NULL;
174			/* sample the divisions */
175			arad = 0.0;
176			if ((dp = div) == NULL)
177			dp = &dnew;
178			for (i = 0; i < hemi.nt; i++)
179			for (j = 0; j < hemi.np; j++) {
180			dp->t = i; dp->p = j;
181			setcolor(dp->v, 0.0, 0.0, 0.0);
182	greg	1.2	dp->r = 0.0;
183	greg	1.1	dp->n = 0;
184	greg	1.4	if (divsample(dp, &hemi, r) < 0)
185	greg	1.1	goto oopsy;
186	greg	2.6	arad += dp->r;
187	greg	1.1	if (div != NULL)
188			dp++;
189	greg	2.6	else
190	greg	1.1	addcolor(acol, dp->v);
191			}
192	greg	2.15	if (hemi.ns > 0 && arad > FTINY && ndivs/arad < minarad)
193			hemi.ns = 0; /* close enough */
194			else if (hemi.ns > 0) { /* else perform super-sampling */
195	greg	1.4	comperrs(div, &hemi); /* compute errors */
196	greg	1.1	qsort(div, ndivs, sizeof(AMBSAMP), ambcmp); /* sort divs */
197			/* super-sample */
198	greg	2.15	for (i = hemi.ns; i > 0; i--) {
199	schorsch	2.11	dnew = *div;
200	greg	1.4	if (divsample(&dnew, &hemi, r) < 0)
201	greg	1.1	goto oopsy;
202			/* reinsert */
203			dp = div;
204			j = ndivs < i ? ndivs : i;
205			while (--j > 0 && dnew.k < dp[1].k) {
206	schorsch	2.11	dp = (dp+1);
207	greg	1.1	dp++;
208			}
209	schorsch	2.11	*dp = dnew;
210	greg	1.1	}
211	greg	1.2	if (pg != NULL \|\| dg != NULL) /* restore order */
212	greg	1.1	qsort(div, ndivs, sizeof(AMBSAMP), ambnorm);
213			}
214			/* compute returned values */
215	greg	1.3	if (div != NULL) {
216	greg	2.6	arad = 0.0;
217	greg	1.3	for (i = ndivs, dp = div; i-- > 0; dp++) {
218			arad += dp->r;
219			if (dp->n > 1) {
220			b = 1.0/dp->n;
221			scalecolor(dp->v, b);
222			dp->r *= b;
223			dp->n = 1;
224			}
225			addcolor(acol, dp->v);
226			}
227	greg	1.5	b = bright(acol);
228	greg	1.6	if (b > FTINY) {
229	greg	1.5	b = ndivs/b;
230	greg	1.6	if (pg != NULL) {
231			posgradient(pg, div, &hemi);
232			for (i = 0; i < 3; i++)
233			pg[i] *= b;
234			}
235			if (dg != NULL) {
236			dirgradient(dg, div, &hemi);
237			for (i = 0; i < 3; i++)
238			dg[i] *= b;
239			}
240			} else {
241			if (pg != NULL)
242			for (i = 0; i < 3; i++)
243			pg[i] = 0.0;
244			if (dg != NULL)
245			for (i = 0; i < 3; i++)
246			dg[i] = 0.0;
247	greg	1.5	}
248	greg	2.9	free((void *)div);
249	greg	1.3	}
250	greg	1.1	b = 1.0/ndivs;
251			scalecolor(acol, b);
252			if (arad <= FTINY)
253	greg	1.16	arad = maxarad;
254	greg	2.3	else
255	greg	2.15	arad = (ndivs+hemi.ns)/arad;
256	greg	1.15	if (pg != NULL) { /* reduce radius if gradient large */
257			d = DOT(pg,pg);
258			if (daradarad > 1.0)
259			arad = 1.0/sqrt(d);
260			}
261	greg	1.16	if (arad < minarad) {
262	greg	1.1	arad = minarad;
263	greg	1.16	if (pg != NULL && daradarad > 1.0) { /* cap gradient */
264			d = 1.0/arad/sqrt(d);
265			for (i = 0; i < 3; i++)
266			pg[i] *= d;
267			}
268			}
269	greg	2.3	if ((arad /= sqrt(wt)) > maxarad)
270			arad = maxarad;
271			return(arad);
272	greg	1.1	oopsy:
273			if (div != NULL)
274	greg	2.9	free((void *)div);
275	greg	1.1	return(0.0);
276			}
277
278
279	greg	2.9	void
280	greg	2.14	comperrs( /* compute initial error estimates */
281			AMBSAMP da, / assumes standard ordering */
282			register AMBHEMI *hp
283			)
284	greg	1.1	{
285			double b, b2;
286			int i, j;
287			register AMBSAMP *dp;
288			/* sum differences from neighbors */
289			dp = da;
290			for (i = 0; i < hp->nt; i++)
291			for (j = 0; j < hp->np; j++) {
292	greg	1.6	#ifdef DEBUG
293			if (dp->t != i \|\| dp->p != j)
294			error(CONSISTENCY,
295			"division order in comperrs");
296			#endif
297	greg	1.1	b = bright(dp[0].v);
298			if (i > 0) { /* from above */
299			b2 = bright(dp[-hp->np].v) - b;
300			b2 = b2 0.25;
301			dp[0].k += b2;
302			dp[-hp->np].k += b2;
303			}
304			if (j > 0) { /* from behind */
305			b2 = bright(dp[-1].v) - b;
306			b2 = b2 0.25;
307			dp[0].k += b2;
308			dp[-1].k += b2;
309	greg	1.4	} else { /* around */
310			b2 = bright(dp[hp->np-1].v) - b;
311	greg	1.1	b2 = b2 0.25;
312			dp[0].k += b2;
313	greg	1.4	dp[hp->np-1].k += b2;
314	greg	1.1	}
315			dp++;
316			}
317			/* divide by number of neighbors */
318			dp = da;
319			for (j = 0; j < hp->np; j++) /* top row */
320			(dp++)->k *= 1.0/3.0;
321			if (hp->nt < 2)
322			return;
323			for (i = 1; i < hp->nt-1; i++) /* central region */
324			for (j = 0; j < hp->np; j++)
325			(dp++)->k *= 0.25;
326			for (j = 0; j < hp->np; j++) /* bottom row */
327			(dp++)->k *= 1.0/3.0;
328			}
329
330
331	greg	2.9	void
332	greg	2.14	posgradient( /* compute position gradient */
333			FVECT gv,
334			AMBSAMP da, / assumes standard ordering */
335			register AMBHEMI *hp
336			)
337	greg	1.1	{
338	greg	1.2	register int i, j;
339	greg	2.2	double nextsine, lastsine, b, d;
340	greg	1.2	double mag0, mag1;
341			double phi, cosp, sinp, xd, yd;
342			register AMBSAMP *dp;
343
344			xd = yd = 0.0;
345			for (j = 0; j < hp->np; j++) {
346			dp = da + j;
347			mag0 = mag1 = 0.0;
348	greg	2.2	lastsine = 0.0;
349	greg	1.2	for (i = 0; i < hp->nt; i++) {
350			#ifdef DEBUG
351			if (dp->t != i \|\| dp->p != j)
352			error(CONSISTENCY,
353			"division order in posgradient");
354			#endif
355			b = bright(dp->v);
356			if (i > 0) {
357			d = dp[-hp->np].r;
358			if (dp[0].r > d) d = dp[0].r;
359	greg	2.2	/* sin(t)cos(t)^2 /
360			d = lastsine (1.0 - (double)i/hp->nt);
361	greg	1.2	mag0 += d*(b - bright(dp[-hp->np].v));
362			}
363	greg	2.2	nextsine = sqrt((double)(i+1)/hp->nt);
364	greg	1.2	if (j > 0) {
365			d = dp[-1].r;
366			if (dp[0].r > d) d = dp[0].r;
367	greg	2.2	mag1 += d * (nextsine - lastsine) *
368			(b - bright(dp[-1].v));
369	greg	1.2	} else {
370			d = dp[hp->np-1].r;
371			if (dp[0].r > d) d = dp[0].r;
372	greg	2.2	mag1 += d * (nextsine - lastsine) *
373			(b - bright(dp[hp->np-1].v));
374	greg	1.2	}
375			dp += hp->np;
376	greg	2.2	lastsine = nextsine;
377	greg	1.2	}
378	greg	2.2	mag0 = 2.0PI / hp->np;
379	greg	1.2	phi = 2.0PI (double)j/hp->np;
380	gwlarson	2.8	cosp = tcos(phi); sinp = tsin(phi);
381	greg	1.2	xd += mag0cosp - mag1sinp;
382			yd += mag0sinp + mag1cosp;
383			}
384			for (i = 0; i < 3; i++)
385	greg	1.5	gv[i] = (xdhp->ux[i] + ydhp->uy[i])/PI;
386	greg	1.1	}
387
388
389	greg	2.9	void
390	greg	2.14	dirgradient( /* compute direction gradient */
391			FVECT gv,
392			AMBSAMP da, / assumes standard ordering */
393			register AMBHEMI *hp
394			)
395	greg	1.1	{
396	greg	1.2	register int i, j;
397			double mag;
398			double phi, xd, yd;
399			register AMBSAMP *dp;
400
401			xd = yd = 0.0;
402			for (j = 0; j < hp->np; j++) {
403			dp = da + j;
404			mag = 0.0;
405			for (i = 0; i < hp->nt; i++) {
406			#ifdef DEBUG
407			if (dp->t != i \|\| dp->p != j)
408			error(CONSISTENCY,
409			"division order in dirgradient");
410			#endif
411	greg	2.2	/* tan(t) */
412			mag += bright(dp->v)/sqrt(hp->nt/(i+.5) - 1.0);
413	greg	1.2	dp += hp->np;
414			}
415			phi = 2.0PI (j+.5)/hp->np + PI/2.0;
416	gwlarson	2.8	xd += mag * tcos(phi);
417			yd += mag * tsin(phi);
418	greg	1.2	}
419			for (i = 0; i < 3; i++)
420	greg	2.2	gv[i] = (xdhp->ux[i] + ydhp->uy[i])/(hp->nt*hp->np);
421	greg	1.1	}