src/rt/ambcomp.c

#ifndef lint
static const char       RCSid[] = "$Id: ambcomp.c,v 2.13 2005/04/13 23:00:59 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"


int
inithemi(                       /* initialize sampling hemisphere */
        register AMBHEMI  *hp,
        RAY  *r,
        COLOR ac, 
        double  wt
)
{
        int     ns;
        double  d;
        register int  i;
                                        /* set number of divisions */
        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 */
        ns = ambssamp * wt + 0.5;
                                        /* assign coefficient */
        d = 1.0/(hp->nt*hp->np + ns);   /* XXX weight not uniform if ns > 0 */
        copycolor(hp->acoef, ac);
        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);
        return(ns);
}


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;
                                        /* assign coefficient */
        if (ambacc <= FTINY)            /* no storage, so report accurately */
                copycolor(ar.rcoef, h->acoef);
        else                            /* else lie for sake of cache */
                setcolor(ar.rcoef, AVGREFL, AVGREFL, AVGREFL);
        if (rayorigin(&ar, AMBIENT, r, ar.rcoef) < 0)
                return(-1);
        copycolor(ar.rcoef, h->acoef);  /* correct coefficient rtrace output */
        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, ns;
        register int  i, j;
                                        /* initialize color */
        setcolor(acol, 0.0, 0.0, 0.0);
                                        /* initialize hemisphere */
        ns = inithemi(&hemi, r, ac, wt);
        ndivs = hemi.nt * hemi.np;
        if (ndivs == 0)
                return(0.0);
                                        /* allocate super-samples */
        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--) {
                        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+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:	2.14
Committed:	Tue Apr 19 01:15:06 2005 UTC (19 years ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.13:	+105 -74 lines
Log Message:	Extensive changes to enable rtrace -oTW option for tracking ray contributions
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.14	static const char RCSid[] = "$Id: ambcomp.c,v 2.13 2005/04/13 23:00:59 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	2.14	int
20			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	int ns;
28			double d;
29			register int i;
30			/* set number of divisions */
31			hp->nt = sqrt(ambdiv * wt / PI) + 0.5;
32			i = ambacc > FTINY ? 3 : 1; /* minimum number of samples */
33			if (hp->nt < i)
34			hp->nt = i;
35			hp->np = PI * hp->nt + 0.5;
36			/* set number of super-samples */
37			ns = ambssamp * wt + 0.5;
38			/* assign coefficient */
39			d = 1.0/(hp->nthp->np + ns); / XXX weight not uniform if ns > 0 */
40			copycolor(hp->acoef, ac);
41			scalecolor(hp->acoef, d);
42			/* 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			return(ns);
55	greg	1.1	}
56
57
58	greg	2.9	int
59	greg	2.14	divsample( /* sample a division */
60			register AMBSAMP *dp,
61			AMBHEMI *h,
62			RAY *r
63			)
64	greg	1.1	{
65			RAY ar;
66	greg	1.11	int hlist[3];
67			double spt[2];
68	greg	1.1	double xd, yd, zd;
69			double b2;
70			double phi;
71	greg	1.2	register int i;
72	greg	2.14	/* assign coefficient */
73			if (ambacc <= FTINY) /* no storage, so report accurately */
74			copycolor(ar.rcoef, h->acoef);
75			else /* else lie for sake of cache */
76			setcolor(ar.rcoef, AVGREFL, AVGREFL, AVGREFL);
77			if (rayorigin(&ar, AMBIENT, r, ar.rcoef) < 0)
78	greg	1.4	return(-1);
79	greg	2.14	copycolor(ar.rcoef, h->acoef); /* correct coefficient rtrace output */
80	greg	1.1	hlist[0] = r->rno;
81			hlist[1] = dp->t;
82			hlist[2] = dp->p;
83	greg	1.13	multisamp(spt, 2, urand(ilhash(hlist,3)+dp->n));
84	greg	1.11	zd = sqrt((dp->t + spt[0])/h->nt);
85			phi = 2.0PI (dp->p + spt[1])/h->np;
86	gwlarson	2.8	xd = tcos(phi) * zd;
87			yd = tsin(phi) * zd;
88	greg	1.1	zd = sqrt(1.0 - zd*zd);
89	greg	1.2	for (i = 0; i < 3; i++)
90			ar.rdir[i] = xd*h->ux[i] +
91			yd*h->uy[i] +
92			zd*h->uz[i];
93			dimlist[ndims++] = dp->t*h->np + dp->p + 90171;
94	greg	1.1	rayvalue(&ar);
95			ndims--;
96			addcolor(dp->v, ar.rcol);
97	greg	2.9	/* use rt to improve gradient calc */
98			if (ar.rt > FTINY && ar.rt < FHUGE)
99			dp->r += 1.0/ar.rt;
100	greg	1.1	/* (re)initialize error */
101			if (dp->n++) {
102			b2 = bright(dp->v)/dp->n - bright(ar.rcol);
103			b2 = b2b2 + dp->k((dp->n-1)*(dp->n-1));
104			dp->k = b2/(dp->n*dp->n);
105			} else
106			dp->k = 0.0;
107	greg	1.4	return(0);
108	greg	1.1	}
109
110
111	greg	2.14	static int
112			ambcmp( /* decreasing order */
113			const void *p1,
114			const void *p2
115			)
116			{
117			const AMBSAMP d1 = (const AMBSAMP )p1;
118			const AMBSAMP d2 = (const AMBSAMP )p2;
119
120			if (d1->k < d2->k)
121			return(1);
122			if (d1->k > d2->k)
123			return(-1);
124			return(0);
125			}
126
127
128			static int
129			ambnorm( /* standard order */
130			const void *p1,
131			const void *p2
132			)
133			{
134			const AMBSAMP d1 = (const AMBSAMP )p1;
135			const AMBSAMP d2 = (const AMBSAMP )p2;
136			register int c;
137
138			if ( (c = d1->t - d2->t) )
139			return(c);
140			return(d1->p - d2->p);
141			}
142
143
144	greg	1.1	double
145	greg	2.14	doambient( /* compute ambient component */
146			COLOR acol,
147			RAY *r,
148			COLOR ac,
149			double wt,
150			FVECT pg,
151			FVECT dg
152			)
153	greg	1.1	{
154			double b, d;
155			AMBHEMI hemi;
156			AMBSAMP *div;
157			AMBSAMP dnew;
158			register AMBSAMP *dp;
159			double arad;
160			int ndivs, ns;
161			register int i, j;
162			/* initialize color */
163			setcolor(acol, 0.0, 0.0, 0.0);
164			/* initialize hemisphere */
165	greg	2.14	ns = inithemi(&hemi, r, ac, wt);
166	greg	1.1	ndivs = hemi.nt * hemi.np;
167			if (ndivs == 0)
168			return(0.0);
169	greg	2.14	/* allocate super-samples */
170	greg	1.1	if (ns > 0 \|\| pg != NULL \|\| dg != NULL) {
171			div = (AMBSAMP )malloc(ndivssizeof(AMBSAMP));
172			if (div == NULL)
173			error(SYSTEM, "out of memory in doambient");
174			} else
175			div = NULL;
176			/* sample the divisions */
177			arad = 0.0;
178			if ((dp = div) == NULL)
179			dp = &dnew;
180			for (i = 0; i < hemi.nt; i++)
181			for (j = 0; j < hemi.np; j++) {
182			dp->t = i; dp->p = j;
183			setcolor(dp->v, 0.0, 0.0, 0.0);
184	greg	1.2	dp->r = 0.0;
185	greg	1.1	dp->n = 0;
186	greg	1.4	if (divsample(dp, &hemi, r) < 0)
187	greg	1.1	goto oopsy;
188	greg	2.6	arad += dp->r;
189	greg	1.1	if (div != NULL)
190			dp++;
191	greg	2.6	else
192	greg	1.1	addcolor(acol, dp->v);
193			}
194	greg	2.5	if (ns > 0 && arad > FTINY && ndivs/arad < minarad)
195			ns = 0; /* close enough */
196			else if (ns > 0) { /* else perform super-sampling */
197	greg	1.4	comperrs(div, &hemi); /* compute errors */
198	greg	1.1	qsort(div, ndivs, sizeof(AMBSAMP), ambcmp); /* sort divs */
199			/* super-sample */
200			for (i = ns; i > 0; i--) {
201	schorsch	2.11	dnew = *div;
202	greg	1.4	if (divsample(&dnew, &hemi, r) < 0)
203	greg	1.1	goto oopsy;
204			/* reinsert */
205			dp = div;
206			j = ndivs < i ? ndivs : i;
207			while (--j > 0 && dnew.k < dp[1].k) {
208	schorsch	2.11	dp = (dp+1);
209	greg	1.1	dp++;
210			}
211	schorsch	2.11	*dp = dnew;
212	greg	1.1	}
213	greg	1.2	if (pg != NULL \|\| dg != NULL) /* restore order */
214	greg	1.1	qsort(div, ndivs, sizeof(AMBSAMP), ambnorm);
215			}
216			/* compute returned values */
217	greg	1.3	if (div != NULL) {
218	greg	2.6	arad = 0.0;
219	greg	1.3	for (i = ndivs, dp = div; i-- > 0; dp++) {
220			arad += dp->r;
221			if (dp->n > 1) {
222			b = 1.0/dp->n;
223			scalecolor(dp->v, b);
224			dp->r *= b;
225			dp->n = 1;
226			}
227			addcolor(acol, dp->v);
228			}
229	greg	1.5	b = bright(acol);
230	greg	1.6	if (b > FTINY) {
231	greg	1.5	b = ndivs/b;
232	greg	1.6	if (pg != NULL) {
233			posgradient(pg, div, &hemi);
234			for (i = 0; i < 3; i++)
235			pg[i] *= b;
236			}
237			if (dg != NULL) {
238			dirgradient(dg, div, &hemi);
239			for (i = 0; i < 3; i++)
240			dg[i] *= b;
241			}
242			} else {
243			if (pg != NULL)
244			for (i = 0; i < 3; i++)
245			pg[i] = 0.0;
246			if (dg != NULL)
247			for (i = 0; i < 3; i++)
248			dg[i] = 0.0;
249	greg	1.5	}
250	greg	2.9	free((void *)div);
251	greg	1.3	}
252	greg	1.1	b = 1.0/ndivs;
253			scalecolor(acol, b);
254			if (arad <= FTINY)
255	greg	1.16	arad = maxarad;
256	greg	2.3	else
257	greg	1.1	arad = (ndivs+ns)/arad;
258	greg	1.15	if (pg != NULL) { /* reduce radius if gradient large */
259			d = DOT(pg,pg);
260			if (daradarad > 1.0)
261			arad = 1.0/sqrt(d);
262			}
263	greg	1.16	if (arad < minarad) {
264	greg	1.1	arad = minarad;
265	greg	1.16	if (pg != NULL && daradarad > 1.0) { /* cap gradient */
266			d = 1.0/arad/sqrt(d);
267			for (i = 0; i < 3; i++)
268			pg[i] *= d;
269			}
270			}
271	greg	2.3	if ((arad /= sqrt(wt)) > maxarad)
272			arad = maxarad;
273			return(arad);
274	greg	1.1	oopsy:
275			if (div != NULL)
276	greg	2.9	free((void *)div);
277	greg	1.1	return(0.0);
278			}
279
280
281	greg	2.9	void
282	greg	2.14	comperrs( /* compute initial error estimates */
283			AMBSAMP da, / assumes standard ordering */
284			register AMBHEMI *hp
285			)
286	greg	1.1	{
287			double b, b2;
288			int i, j;
289			register AMBSAMP *dp;
290			/* sum differences from neighbors */
291			dp = da;
292			for (i = 0; i < hp->nt; i++)
293			for (j = 0; j < hp->np; j++) {
294	greg	1.6	#ifdef DEBUG
295			if (dp->t != i \|\| dp->p != j)
296			error(CONSISTENCY,
297			"division order in comperrs");
298			#endif
299	greg	1.1	b = bright(dp[0].v);
300			if (i > 0) { /* from above */
301			b2 = bright(dp[-hp->np].v) - b;
302			b2 = b2 0.25;
303			dp[0].k += b2;
304			dp[-hp->np].k += b2;
305			}
306			if (j > 0) { /* from behind */
307			b2 = bright(dp[-1].v) - b;
308			b2 = b2 0.25;
309			dp[0].k += b2;
310			dp[-1].k += b2;
311	greg	1.4	} else { /* around */
312			b2 = bright(dp[hp->np-1].v) - b;
313	greg	1.1	b2 = b2 0.25;
314			dp[0].k += b2;
315	greg	1.4	dp[hp->np-1].k += b2;
316	greg	1.1	}
317			dp++;
318			}
319			/* divide by number of neighbors */
320			dp = da;
321			for (j = 0; j < hp->np; j++) /* top row */
322			(dp++)->k *= 1.0/3.0;
323			if (hp->nt < 2)
324			return;
325			for (i = 1; i < hp->nt-1; i++) /* central region */
326			for (j = 0; j < hp->np; j++)
327			(dp++)->k *= 0.25;
328			for (j = 0; j < hp->np; j++) /* bottom row */
329			(dp++)->k *= 1.0/3.0;
330			}
331
332
333	greg	2.9	void
334	greg	2.14	posgradient( /* compute position gradient */
335			FVECT gv,
336			AMBSAMP da, / assumes standard ordering */
337			register AMBHEMI *hp
338			)
339	greg	1.1	{
340	greg	1.2	register int i, j;
341	greg	2.2	double nextsine, lastsine, b, d;
342	greg	1.2	double mag0, mag1;
343			double phi, cosp, sinp, xd, yd;
344			register AMBSAMP *dp;
345
346			xd = yd = 0.0;
347			for (j = 0; j < hp->np; j++) {
348			dp = da + j;
349			mag0 = mag1 = 0.0;
350	greg	2.2	lastsine = 0.0;
351	greg	1.2	for (i = 0; i < hp->nt; i++) {
352			#ifdef DEBUG
353			if (dp->t != i \|\| dp->p != j)
354			error(CONSISTENCY,
355			"division order in posgradient");
356			#endif
357			b = bright(dp->v);
358			if (i > 0) {
359			d = dp[-hp->np].r;
360			if (dp[0].r > d) d = dp[0].r;
361	greg	2.2	/* sin(t)cos(t)^2 /
362			d = lastsine (1.0 - (double)i/hp->nt);
363	greg	1.2	mag0 += d*(b - bright(dp[-hp->np].v));
364			}
365	greg	2.2	nextsine = sqrt((double)(i+1)/hp->nt);
366	greg	1.2	if (j > 0) {
367			d = dp[-1].r;
368			if (dp[0].r > d) d = dp[0].r;
369	greg	2.2	mag1 += d * (nextsine - lastsine) *
370			(b - bright(dp[-1].v));
371	greg	1.2	} else {
372			d = dp[hp->np-1].r;
373			if (dp[0].r > d) d = dp[0].r;
374	greg	2.2	mag1 += d * (nextsine - lastsine) *
375			(b - bright(dp[hp->np-1].v));
376	greg	1.2	}
377			dp += hp->np;
378	greg	2.2	lastsine = nextsine;
379	greg	1.2	}
380	greg	2.2	mag0 = 2.0PI / hp->np;
381	greg	1.2	phi = 2.0PI (double)j/hp->np;
382	gwlarson	2.8	cosp = tcos(phi); sinp = tsin(phi);
383	greg	1.2	xd += mag0cosp - mag1sinp;
384			yd += mag0sinp + mag1cosp;
385			}
386			for (i = 0; i < 3; i++)
387	greg	1.5	gv[i] = (xdhp->ux[i] + ydhp->uy[i])/PI;
388	greg	1.1	}
389
390
391	greg	2.9	void
392	greg	2.14	dirgradient( /* compute direction gradient */
393			FVECT gv,
394			AMBSAMP da, / assumes standard ordering */
395			register AMBHEMI *hp
396			)
397	greg	1.1	{
398	greg	1.2	register int i, j;
399			double mag;
400			double phi, xd, yd;
401			register AMBSAMP *dp;
402
403			xd = yd = 0.0;
404			for (j = 0; j < hp->np; j++) {
405			dp = da + j;
406			mag = 0.0;
407			for (i = 0; i < hp->nt; i++) {
408			#ifdef DEBUG
409			if (dp->t != i \|\| dp->p != j)
410			error(CONSISTENCY,
411			"division order in dirgradient");
412			#endif
413	greg	2.2	/* tan(t) */
414			mag += bright(dp->v)/sqrt(hp->nt/(i+.5) - 1.0);
415	greg	1.2	dp += hp->np;
416			}
417			phi = 2.0PI (j+.5)/hp->np + PI/2.0;
418	gwlarson	2.8	xd += mag * tcos(phi);
419			yd += mag * tsin(phi);
420	greg	1.2	}
421			for (i = 0; i < 3; i++)
422	greg	2.2	gv[i] = (xdhp->ux[i] + ydhp->uy[i])/(hp->nt*hp->np);
423	greg	1.1	}