src/rt/ambcomp.c

#ifndef lint
static const char       RCSid[] = "$Id: ambcomp.c,v 2.12 2003/07/27 22:12:03 schorsch 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"


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--) {
                        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
inithemi(hp, r, wt)             /* initialize sampling hemisphere */
register AMBHEMI  *hp;
RAY  *r;
double  wt;
{
        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;
                                        /* 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:	2.13
Committed:	Wed Apr 13 23:00:59 2005 UTC (19 years ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.12:	+4 -5 lines
Log Message:	Changed minimum number of ambient rays
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.13	static const char RCSid[] = "$Id: ambcomp.c,v 2.12 2003/07/27 22:12:03 schorsch 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			static int
20			ambcmp(d1, d2) /* decreasing order */
21			AMBSAMP d1, d2;
22			{
23			if (d1->k < d2->k)
24			return(1);
25			if (d1->k > d2->k)
26			return(-1);
27			return(0);
28			}
29
30
31			static int
32			ambnorm(d1, d2) /* standard order */
33			AMBSAMP d1, d2;
34			{
35			register int c;
36
37	schorsch	2.12	if ( (c = d1->t - d2->t) )
38	greg	1.1	return(c);
39			return(d1->p - d2->p);
40			}
41
42
43	greg	2.9	int
44	greg	1.1	divsample(dp, h, r) /* sample a division */
45			register AMBSAMP *dp;
46			AMBHEMI *h;
47			RAY *r;
48			{
49			RAY ar;
50	greg	1.11	int hlist[3];
51			double spt[2];
52	greg	1.1	double xd, yd, zd;
53			double b2;
54			double phi;
55	greg	1.2	register int i;
56	greg	1.1
57	greg	1.12	if (rayorigin(&ar, r, AMBIENT, AVGREFL) < 0)
58	greg	1.4	return(-1);
59	greg	1.1	hlist[0] = r->rno;
60			hlist[1] = dp->t;
61			hlist[2] = dp->p;
62	greg	1.13	multisamp(spt, 2, urand(ilhash(hlist,3)+dp->n));
63	greg	1.11	zd = sqrt((dp->t + spt[0])/h->nt);
64			phi = 2.0PI (dp->p + spt[1])/h->np;
65	gwlarson	2.8	xd = tcos(phi) * zd;
66			yd = tsin(phi) * zd;
67	greg	1.1	zd = sqrt(1.0 - zd*zd);
68	greg	1.2	for (i = 0; i < 3; i++)
69			ar.rdir[i] = xd*h->ux[i] +
70			yd*h->uy[i] +
71			zd*h->uz[i];
72			dimlist[ndims++] = dp->t*h->np + dp->p + 90171;
73	greg	1.1	rayvalue(&ar);
74			ndims--;
75			addcolor(dp->v, ar.rcol);
76	greg	2.9	/* use rt to improve gradient calc */
77			if (ar.rt > FTINY && ar.rt < FHUGE)
78			dp->r += 1.0/ar.rt;
79	greg	1.1	/* (re)initialize error */
80			if (dp->n++) {
81			b2 = bright(dp->v)/dp->n - bright(ar.rcol);
82			b2 = b2b2 + dp->k((dp->n-1)*(dp->n-1));
83			dp->k = b2/(dp->n*dp->n);
84			} else
85			dp->k = 0.0;
86	greg	1.4	return(0);
87	greg	1.1	}
88
89
90			double
91	greg	1.12	doambient(acol, r, wt, pg, dg) /* compute ambient component */
92	greg	1.1	COLOR acol;
93			RAY *r;
94	greg	1.12	double wt;
95	greg	1.1	FVECT pg, dg;
96			{
97			double b, d;
98			AMBHEMI hemi;
99			AMBSAMP *div;
100			AMBSAMP dnew;
101			register AMBSAMP *dp;
102			double arad;
103			int ndivs, ns;
104			register int i, j;
105			/* initialize color */
106			setcolor(acol, 0.0, 0.0, 0.0);
107			/* initialize hemisphere */
108	greg	1.12	inithemi(&hemi, r, wt);
109	greg	1.1	ndivs = hemi.nt * hemi.np;
110			if (ndivs == 0)
111			return(0.0);
112			/* set number of super-samples */
113	greg	1.12	ns = ambssamp * wt + 0.5;
114	greg	1.1	if (ns > 0 \|\| pg != NULL \|\| dg != NULL) {
115			div = (AMBSAMP )malloc(ndivssizeof(AMBSAMP));
116			if (div == NULL)
117			error(SYSTEM, "out of memory in doambient");
118			} else
119			div = NULL;
120			/* sample the divisions */
121			arad = 0.0;
122			if ((dp = div) == NULL)
123			dp = &dnew;
124			for (i = 0; i < hemi.nt; i++)
125			for (j = 0; j < hemi.np; j++) {
126			dp->t = i; dp->p = j;
127			setcolor(dp->v, 0.0, 0.0, 0.0);
128	greg	1.2	dp->r = 0.0;
129	greg	1.1	dp->n = 0;
130	greg	1.4	if (divsample(dp, &hemi, r) < 0)
131	greg	1.1	goto oopsy;
132	greg	2.6	arad += dp->r;
133	greg	1.1	if (div != NULL)
134			dp++;
135	greg	2.6	else
136	greg	1.1	addcolor(acol, dp->v);
137			}
138	greg	2.5	if (ns > 0 && arad > FTINY && ndivs/arad < minarad)
139			ns = 0; /* close enough */
140			else if (ns > 0) { /* else perform super-sampling */
141	greg	1.4	comperrs(div, &hemi); /* compute errors */
142	greg	1.1	qsort(div, ndivs, sizeof(AMBSAMP), ambcmp); /* sort divs */
143			/* super-sample */
144			for (i = ns; i > 0; i--) {
145	schorsch	2.11	dnew = *div;
146	greg	1.4	if (divsample(&dnew, &hemi, r) < 0)
147	greg	1.1	goto oopsy;
148			/* reinsert */
149			dp = div;
150			j = ndivs < i ? ndivs : i;
151			while (--j > 0 && dnew.k < dp[1].k) {
152	schorsch	2.11	dp = (dp+1);
153	greg	1.1	dp++;
154			}
155	schorsch	2.11	*dp = dnew;
156	greg	1.1	}
157	greg	1.2	if (pg != NULL \|\| dg != NULL) /* restore order */
158	greg	1.1	qsort(div, ndivs, sizeof(AMBSAMP), ambnorm);
159			}
160			/* compute returned values */
161	greg	1.3	if (div != NULL) {
162	greg	2.6	arad = 0.0;
163	greg	1.3	for (i = ndivs, dp = div; i-- > 0; dp++) {
164			arad += dp->r;
165			if (dp->n > 1) {
166			b = 1.0/dp->n;
167			scalecolor(dp->v, b);
168			dp->r *= b;
169			dp->n = 1;
170			}
171			addcolor(acol, dp->v);
172			}
173	greg	1.5	b = bright(acol);
174	greg	1.6	if (b > FTINY) {
175	greg	1.5	b = ndivs/b;
176	greg	1.6	if (pg != NULL) {
177			posgradient(pg, div, &hemi);
178			for (i = 0; i < 3; i++)
179			pg[i] *= b;
180			}
181			if (dg != NULL) {
182			dirgradient(dg, div, &hemi);
183			for (i = 0; i < 3; i++)
184			dg[i] *= b;
185			}
186			} else {
187			if (pg != NULL)
188			for (i = 0; i < 3; i++)
189			pg[i] = 0.0;
190			if (dg != NULL)
191			for (i = 0; i < 3; i++)
192			dg[i] = 0.0;
193	greg	1.5	}
194	greg	2.9	free((void *)div);
195	greg	1.3	}
196	greg	1.1	b = 1.0/ndivs;
197			scalecolor(acol, b);
198			if (arad <= FTINY)
199	greg	1.16	arad = maxarad;
200	greg	2.3	else
201	greg	1.1	arad = (ndivs+ns)/arad;
202	greg	1.15	if (pg != NULL) { /* reduce radius if gradient large */
203			d = DOT(pg,pg);
204			if (daradarad > 1.0)
205			arad = 1.0/sqrt(d);
206			}
207	greg	1.16	if (arad < minarad) {
208	greg	1.1	arad = minarad;
209	greg	1.16	if (pg != NULL && daradarad > 1.0) { /* cap gradient */
210			d = 1.0/arad/sqrt(d);
211			for (i = 0; i < 3; i++)
212			pg[i] *= d;
213			}
214			}
215	greg	2.3	if ((arad /= sqrt(wt)) > maxarad)
216			arad = maxarad;
217			return(arad);
218	greg	1.1	oopsy:
219			if (div != NULL)
220	greg	2.9	free((void *)div);
221	greg	1.1	return(0.0);
222			}
223
224
225	greg	2.9	void
226	greg	1.12	inithemi(hp, r, wt) /* initialize sampling hemisphere */
227	greg	1.1	register AMBHEMI *hp;
228			RAY *r;
229	greg	1.12	double wt;
230	greg	1.1	{
231	greg	1.2	register int i;
232	greg	1.1	/* set number of divisions */
233	greg	1.12	hp->nt = sqrt(ambdiv * wt / PI) + 0.5;
234	greg	2.13	i = ambacc > FTINY ? 3 : 1; /* minimum number of samples */
235			if (hp->nt < i)
236			hp->nt = i;
237	greg	1.14	hp->np = PI * hp->nt + 0.5;
238	greg	1.1	/* make axes */
239			VCOPY(hp->uz, r->ron);
240			hp->uy[0] = hp->uy[1] = hp->uy[2] = 0.0;
241	greg	1.2	for (i = 0; i < 3; i++)
242			if (hp->uz[i] < 0.6 && hp->uz[i] > -0.6)
243	greg	1.1	break;
244	greg	1.2	if (i >= 3)
245	greg	1.1	error(CONSISTENCY, "bad ray direction in inithemi");
246	greg	1.2	hp->uy[i] = 1.0;
247	greg	1.3	fcross(hp->ux, hp->uy, hp->uz);
248			normalize(hp->ux);
249			fcross(hp->uy, hp->uz, hp->ux);
250	greg	1.1	}
251
252
253	greg	2.9	void
254	greg	1.1	comperrs(da, hp) /* compute initial error estimates */
255	greg	1.2	AMBSAMP da; / assumes standard ordering */
256	greg	1.1	register AMBHEMI *hp;
257			{
258			double b, b2;
259			int i, j;
260			register AMBSAMP *dp;
261			/* sum differences from neighbors */
262			dp = da;
263			for (i = 0; i < hp->nt; i++)
264			for (j = 0; j < hp->np; j++) {
265	greg	1.6	#ifdef DEBUG
266			if (dp->t != i \|\| dp->p != j)
267			error(CONSISTENCY,
268			"division order in comperrs");
269			#endif
270	greg	1.1	b = bright(dp[0].v);
271			if (i > 0) { /* from above */
272			b2 = bright(dp[-hp->np].v) - b;
273			b2 = b2 0.25;
274			dp[0].k += b2;
275			dp[-hp->np].k += b2;
276			}
277			if (j > 0) { /* from behind */
278			b2 = bright(dp[-1].v) - b;
279			b2 = b2 0.25;
280			dp[0].k += b2;
281			dp[-1].k += b2;
282	greg	1.4	} else { /* around */
283			b2 = bright(dp[hp->np-1].v) - b;
284	greg	1.1	b2 = b2 0.25;
285			dp[0].k += b2;
286	greg	1.4	dp[hp->np-1].k += b2;
287	greg	1.1	}
288			dp++;
289			}
290			/* divide by number of neighbors */
291			dp = da;
292			for (j = 0; j < hp->np; j++) /* top row */
293			(dp++)->k *= 1.0/3.0;
294			if (hp->nt < 2)
295			return;
296			for (i = 1; i < hp->nt-1; i++) /* central region */
297			for (j = 0; j < hp->np; j++)
298			(dp++)->k *= 0.25;
299			for (j = 0; j < hp->np; j++) /* bottom row */
300			(dp++)->k *= 1.0/3.0;
301			}
302
303
304	greg	2.9	void
305	greg	1.1	posgradient(gv, da, hp) /* compute position gradient */
306			FVECT gv;
307	greg	1.2	AMBSAMP da; / assumes standard ordering */
308	greg	2.2	register AMBHEMI *hp;
309	greg	1.1	{
310	greg	1.2	register int i, j;
311	greg	2.2	double nextsine, lastsine, b, d;
312	greg	1.2	double mag0, mag1;
313			double phi, cosp, sinp, xd, yd;
314			register AMBSAMP *dp;
315
316			xd = yd = 0.0;
317			for (j = 0; j < hp->np; j++) {
318			dp = da + j;
319			mag0 = mag1 = 0.0;
320	greg	2.2	lastsine = 0.0;
321	greg	1.2	for (i = 0; i < hp->nt; i++) {
322			#ifdef DEBUG
323			if (dp->t != i \|\| dp->p != j)
324			error(CONSISTENCY,
325			"division order in posgradient");
326			#endif
327			b = bright(dp->v);
328			if (i > 0) {
329			d = dp[-hp->np].r;
330			if (dp[0].r > d) d = dp[0].r;
331	greg	2.2	/* sin(t)cos(t)^2 /
332			d = lastsine (1.0 - (double)i/hp->nt);
333	greg	1.2	mag0 += d*(b - bright(dp[-hp->np].v));
334			}
335	greg	2.2	nextsine = sqrt((double)(i+1)/hp->nt);
336	greg	1.2	if (j > 0) {
337			d = dp[-1].r;
338			if (dp[0].r > d) d = dp[0].r;
339	greg	2.2	mag1 += d * (nextsine - lastsine) *
340			(b - bright(dp[-1].v));
341	greg	1.2	} else {
342			d = dp[hp->np-1].r;
343			if (dp[0].r > d) d = dp[0].r;
344	greg	2.2	mag1 += d * (nextsine - lastsine) *
345			(b - bright(dp[hp->np-1].v));
346	greg	1.2	}
347			dp += hp->np;
348	greg	2.2	lastsine = nextsine;
349	greg	1.2	}
350	greg	2.2	mag0 = 2.0PI / hp->np;
351	greg	1.2	phi = 2.0PI (double)j/hp->np;
352	gwlarson	2.8	cosp = tcos(phi); sinp = tsin(phi);
353	greg	1.2	xd += mag0cosp - mag1sinp;
354			yd += mag0sinp + mag1cosp;
355			}
356			for (i = 0; i < 3; i++)
357	greg	1.5	gv[i] = (xdhp->ux[i] + ydhp->uy[i])/PI;
358	greg	1.1	}
359
360
361	greg	2.9	void
362	greg	1.1	dirgradient(gv, da, hp) /* compute direction gradient */
363			FVECT gv;
364	greg	1.2	AMBSAMP da; / assumes standard ordering */
365	greg	2.2	register AMBHEMI *hp;
366	greg	1.1	{
367	greg	1.2	register int i, j;
368			double mag;
369			double phi, 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			mag = 0.0;
376			for (i = 0; i < hp->nt; i++) {
377			#ifdef DEBUG
378			if (dp->t != i \|\| dp->p != j)
379			error(CONSISTENCY,
380			"division order in dirgradient");
381			#endif
382	greg	2.2	/* tan(t) */
383			mag += bright(dp->v)/sqrt(hp->nt/(i+.5) - 1.0);
384	greg	1.2	dp += hp->np;
385			}
386			phi = 2.0PI (j+.5)/hp->np + PI/2.0;
387	gwlarson	2.8	xd += mag * tcos(phi);
388			yd += mag * tsin(phi);
389	greg	1.2	}
390			for (i = 0; i < 3; i++)
391	greg	2.2	gv[i] = (xdhp->ux[i] + ydhp->uy[i])/(hp->nt*hp->np);
392	greg	1.1	}