src/gen/mkillum2.c

/* Copyright (c) 1991 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 * Routines to do the actual calculation for mkillum
 */

#include  "mkillum.h"

#include  "face.h"

#include  "cone.h"

#include  "random.h"


o_default(ob, il, rt, nm)       /* default illum action */
OBJREC  *ob;
struct illum_args  *il;
struct rtproc  *rt;
char  *nm;
{
        sprintf(errmsg, "(%s): cannot make illum for %s \"%s\"",
                        nm, ofun[ob->otype].funame, ob->oname);
        error(WARNING, errmsg);
        printobj(il->altmat, ob);
}


o_face(ob, il, rt, nm)          /* make an illum face */
OBJREC  *ob;
struct illum_args  *il;
struct rtproc  *rt;
char  *nm;
{
#define MAXMISS         (5*n*il->nsamps)
        int  dim[3];
        int  n, nalt, nazi, h;
        float  *distarr;
        double  sp[2], r1, r2;
        FVECT  dn, org, dir;
        FVECT  u, v;
        double  ur[2], vr[2];
        int  nmisses;
        register FACE  *fa;
        register int  i, j;
                                /* get/check arguments */
        fa = getface(ob);
        if (fa->area == 0.0) {
                freeface(ob);
                o_default(ob, il, rt, nm);
                return;
        }
                                /* set up sampling */
        if (il->sampdens <= 0)
                nalt = nazi = 1;
        else {
                n = PI * il->sampdens;
                nalt = sqrt(n/PI) + .5;
                nazi = PI*nalt + .5;
        }
        n = nalt*nazi;
        distarr = (float *)calloc(n, 3*sizeof(float));
        if (distarr == NULL)
                error(SYSTEM, "out of memory in o_face");
        mkaxes(u, v, fa->norm);
        ur[0] = vr[0] = FHUGE;
        ur[1] = vr[1] = -FHUGE;
        for (i = 0; i < fa->nv; i++) {
                r1 = DOT(VERTEX(fa,i),u);
                if (r1 < ur[0]) ur[0] = r1;
                if (r1 > ur[1]) ur[1] = r1;
                r2 = DOT(VERTEX(fa,i),v);
                if (r2 < vr[0]) vr[0] = r2;
                if (r2 > vr[1]) vr[1] = r2;
        }
        dim[0] = random();
                                /* sample polygon */
        nmisses = 0;
        for (dim[1] = 0; dim[1] < nalt; dim[1]++)
            for (dim[2] = 0; dim[2] < nazi; dim[2]++)
                for (i = 0; i < il->nsamps; i++) {
                                        /* random direction */
                    h = ilhash(dim, 3) + i;
                    multisamp(sp, 2, urand(h));
                    r1 = (dim[1] + sp[0])/nalt;
                    r2 = (dim[2] + sp[1] - .5)/nazi;
                    flatdir(dn, r1, r2);
                    for (j = 0; j < 3; j++)
                        dir[j] = -dn[0]*u[j] - dn[1]*v[j] - dn[2]*fa->norm[j];
                                        /* random location */
                    do {
                        multisamp(sp, 2, urand(h+4862+nmisses));
                        r1 = ur[0] + (ur[1]-ur[0]) * sp[0];
                        r2 = vr[0] + (vr[1]-vr[0]) * sp[1];
                        for (j = 0; j < 3; j++)
                            org[j] = r1*u[j] + r2*v[j]
                                        + fa->offset*fa->norm[j];
                    } while (!inface(org, fa) && nmisses++ < MAXMISS);
                    if (nmisses > MAXMISS) {
                        objerror(ob, WARNING, "bad aspect");
                        rt->nrays = 0;
                        freeface(ob);
                        free((char *)distarr);
                        o_default(ob, il, rt, nm);
                        return;
                    }
                    for (j = 0; j < 3; j++)
                        org[j] += .001*fa->norm[j];
                                        /* send sample */
                    raysamp(distarr+3*(dim[1]*nazi+dim[2]), org, dir, rt);
                }
        rayflush(rt);
                                /* write out the face and its distribution */
        if (average(il, distarr, nalt*nazi)) {
                if (il->sampdens > 0)
                        flatout(il, distarr, nalt, nazi, u, v, fa->norm);
                illumout(il, ob);
        } else
                printobj(il->altmat, ob);
                                /* clean up */
        freeface(ob);
        free((char *)distarr);
#undef MAXMISS
}


o_sphere(ob, il, rt, nm)        /* make an illum sphere */
register OBJREC  *ob;
struct illum_args  *il;
struct rtproc  *rt;
char  *nm;
{
        int  dim[3];
        int  n, nalt, nazi;
        float  *distarr;
        double  sp[4], r1, r2, r3;
        FVECT  org, dir;
        FVECT  u, v;
        register int  i, j;
                                /* check arguments */
        if (ob->oargs.nfargs != 4)
                objerror(ob, USER, "bad # of arguments");
                                /* set up sampling */
        if (il->sampdens <= 0)
                nalt = nazi = 1;
        else {
                n = 4.*PI * il->sampdens;
                nalt = sqrt(n/PI) + .5;
                nazi = PI*nalt + .5;
        }
        n = nalt*nazi;
        distarr = (float *)calloc(n, 3*sizeof(float));
        if (distarr == NULL)
                error(SYSTEM, "out of memory in o_sphere");
        dim[0] = random();
                                /* sample sphere */
        for (dim[1] = 0; dim[1] < nalt; dim[1]++)
            for (dim[2] = 0; dim[2] < nazi; dim[2]++)
                for (i = 0; i < il->nsamps; i++) {
                                        /* next sample point */
                    multisamp(sp, 4, urand(ilhash(dim,3)+i));
                                        /* random direction */
                    r1 = (dim[1] + sp[0])/nalt;
                    r2 = (dim[2] + sp[1] - .5)/nazi;
                    rounddir(dir, r1, r2);
                                        /* random location */
                    mkaxes(u, v, dir);          /* yuck! */
                    r3 = sqrt(sp[2]);
                    r2 = 2.*PI*sp[3];
                    r1 = r3*ob->oargs.farg[3]*cos(r2);
                    r2 = r3*ob->oargs.farg[3]*sin(r2);
                    r3 = ob->oargs.farg[3]*sqrt(1.01-r3*r3);
                    for (j = 0; j < 3; j++) {
                        org[j] = ob->oargs.farg[j] + r1*u[j] + r2*v[j] +
                                        r3*dir[j];
                        dir[j] = -dir[j];
                    }
                                        /* send sample */
                    raysamp(distarr+3*(dim[1]*nazi+dim[2]), org, dir, rt);
                }
        rayflush(rt);
                                /* write out the sphere and its distribution */
        if (average(il, distarr, nalt*nazi)) {
                if (il->sampdens > 0)
                        roundout(il, distarr, nalt, nazi);
                else
                        objerror(ob, WARNING, "diffuse distribution");
                illumout(il, ob);
        } else
                printobj(il->altmat, ob);
                                /* clean up */
        free((char *)distarr);
}


o_ring(ob, il, rt, nm)          /* make an illum ring */
OBJREC  *ob;
struct illum_args  *il;
struct rtproc  *rt;
char  *nm;
{
        int  dim[3];
        int  n, nalt, nazi;
        float  *distarr;
        double  sp[4], r1, r2, r3;
        FVECT  dn, org, dir;
        FVECT  u, v;
        register CONE  *co;
        register int  i, j;
                                /* get/check arguments */
        co = getcone(ob, 0);
                                /* set up sampling */
        if (il->sampdens <= 0)
                nalt = nazi = 1;
        else {
                n = PI * il->sampdens;
                nalt = sqrt(n/PI) + .5;
                nazi = PI*nalt + .5;
        }
        n = nalt*nazi;
        distarr = (float *)calloc(n, 3*sizeof(float));
        if (distarr == NULL)
                error(SYSTEM, "out of memory in o_ring");
        mkaxes(u, v, co->ad);
        dim[0] = random();
                                /* sample disk */
        for (dim[1] = 0; dim[1] < nalt; dim[1]++)
            for (dim[2] = 0; dim[2] < nazi; dim[2]++)
                for (i = 0; i < il->nsamps; i++) {
                                        /* next sample point */
                    multisamp(sp, 4, urand(ilhash(dim,3)+i));
                                        /* random direction */
                    r1 = (dim[1] + sp[0])/nalt;
                    r2 = (dim[2] + sp[1] - .5)/nazi;
                    flatdir(dn, r1, r2);
                    for (j = 0; j < 3; j++)
                        dir[j] = -dn[0]*u[j] - dn[1]*v[j] - dn[2]*co->ad[j];
                                        /* random location */
                    r3 = sqrt(CO_R0(co)*CO_R0(co) +
                            sp[2]*(CO_R1(co)*CO_R1(co) - CO_R0(co)*CO_R0(co)));
                    r2 = 2.*PI*sp[3];
                    r1 = r3*cos(r2);
                    r2 = r3*sin(r2);
                    for (j = 0; j < 3; j++)
                        org[j] = CO_P0(co)[j] + r1*u[j] + r1*v[j] +
                                        .001*co->ad[j];

                                        /* send sample */
                    raysamp(distarr+3*(dim[1]*nazi+dim[2]), org, dir, rt);
                }
        rayflush(rt);
                                /* write out the ring and its distribution */
        if (average(il, distarr, nalt*nazi)) {
                if (il->sampdens > 0)
                        flatout(il, distarr, nalt, nazi, u, v, co->ad);
                illumout(il, ob);
        } else
                printobj(il->altmat, ob);
                                /* clean up */
        freecone(ob);
        free((char *)distarr);
}


raysamp(res, org, dir, rt)      /* compute a ray sample */
float  res[3];
FVECT  org, dir;
register struct rtproc  *rt;
{
        register float  *fp;

        if (rt->nrays == rt->bsiz)
                rayflush(rt);
        rt->dest[rt->nrays] = res;
        fp = rt->buf + 6*rt->nrays++;
        *fp++ = org[0]; *fp++ = org[1]; *fp++ = org[2];
        *fp++ = dir[0]; *fp++ = dir[1]; *fp = dir[2];
}


rayflush(rt)                    /* flush buffered rays */
register struct rtproc  *rt;
{
        register int  i;

        if (rt->nrays <= 0)
                return;
        bzero(rt->buf+6*rt->nrays, 6*sizeof(float));
        errno = 0;
        if ( process(rt->pd, (char *)rt->buf, (char *)rt->buf,
                        3*sizeof(float)*rt->nrays,
                        6*sizeof(float)*(rt->nrays+1)) <
                        3*sizeof(float)*rt->nrays )
                error(SYSTEM, "error reading from rtrace process");
        i = rt->nrays;
        while (i--) {
                rt->dest[i][0] += rt->buf[3*i];
                rt->dest[i][1] += rt->buf[3*i+1];
                rt->dest[i][2] += rt->buf[3*i+2];
        }
        rt->nrays = 0;
}


mkaxes(u, v, n)                 /* compute u and v to go with n */
FVECT  u, v, n;
{
        register int  i;

        v[0] = v[1] = v[2] = 0.0;
        for (i = 0; i < 3; i++)
                if (n[i] < 0.6 && n[i] > -0.6)
                        break;
        v[i] = 1.0;
        fcross(u, v, n);
        normalize(u);
        fcross(v, n, u);
}


rounddir(dv, alt, azi)          /* compute uniform spherical direction */
register FVECT  dv;
double  alt, azi;
{
        double  d1, d2;

        dv[2] = 1. - 2.*alt;
        d1 = sqrt(1. - dv[2]*dv[2]);
        d2 = 2.*PI * azi;
        dv[0] = d1*cos(d2);
        dv[1] = d1*sin(d2);
}


flatdir(dv, alt, azi)           /* compute uniform hemispherical direction */
register FVECT  dv;
double  alt, azi;
{
        double  d1, d2;

        d1 = sqrt(alt);
        d2 = 2.*PI * azi;
        dv[0] = d1*cos(d2);
        dv[1] = d1*sin(d2);
        dv[2] = sqrt(1. - alt);
}
Revision:	2.2
Committed:	Wed Mar 11 12:25:47 1992 UTC (33 years, 7 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.1:	+4 -5 lines
Log Message:	changed so light below threshold is printed as ordinary object
#	User	Rev	Content
1	greg	1.1	/* Copyright (c) 1991 Regents of the University of California */
2
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8	greg	1.4	* Routines to do the actual calculation for mkillum
9	greg	1.1	*/
10
11			#include "mkillum.h"
12
13			#include "face.h"
14
15			#include "cone.h"
16
17	greg	1.2	#include "random.h"
18	greg	1.1
19	greg	1.2
20			o_default(ob, il, rt, nm) /* default illum action */
21	greg	1.1	OBJREC *ob;
22			struct illum_args *il;
23			struct rtproc *rt;
24	greg	1.2	char *nm;
25	greg	1.1	{
26	greg	1.2	sprintf(errmsg, "(%s): cannot make illum for %s \"%s\"",
27			nm, ofun[ob->otype].funame, ob->oname);
28			error(WARNING, errmsg);
29	greg	2.2	printobj(il->altmat, ob);
30	greg	1.2	}
31
32
33			o_face(ob, il, rt, nm) /* make an illum face */
34			OBJREC *ob;
35			struct illum_args *il;
36			struct rtproc *rt;
37			char *nm;
38			{
39	greg	1.3	#define MAXMISS (5nil->nsamps)
40	greg	1.10	int dim[3];
41			int n, nalt, nazi, h;
42	greg	1.3	float *distarr;
43	greg	1.10	double sp[2], r1, r2;
44	greg	1.4	FVECT dn, org, dir;
45	greg	1.3	FVECT u, v;
46			double ur[2], vr[2];
47			int nmisses;
48			register FACE *fa;
49			register int i, j;
50			/* get/check arguments */
51			fa = getface(ob);
52			if (fa->area == 0.0) {
53			freeface(ob);
54			o_default(ob, il, rt, nm);
55			return;
56			}
57			/* set up sampling */
58	greg	1.11	if (il->sampdens <= 0)
59			nalt = nazi = 1;
60			else {
61			n = PI * il->sampdens;
62			nalt = sqrt(n/PI) + .5;
63			nazi = PI*nalt + .5;
64			}
65	greg	1.3	n = nalt*nazi;
66			distarr = (float )calloc(n, 3sizeof(float));
67			if (distarr == NULL)
68			error(SYSTEM, "out of memory in o_face");
69			mkaxes(u, v, fa->norm);
70			ur[0] = vr[0] = FHUGE;
71			ur[1] = vr[1] = -FHUGE;
72			for (i = 0; i < fa->nv; i++) {
73			r1 = DOT(VERTEX(fa,i),u);
74			if (r1 < ur[0]) ur[0] = r1;
75			if (r1 > ur[1]) ur[1] = r1;
76			r2 = DOT(VERTEX(fa,i),v);
77			if (r2 < vr[0]) vr[0] = r2;
78			if (r2 > vr[1]) vr[1] = r2;
79			}
80			dim[0] = random();
81			/* sample polygon */
82			nmisses = 0;
83			for (dim[1] = 0; dim[1] < nalt; dim[1]++)
84			for (dim[2] = 0; dim[2] < nazi; dim[2]++)
85			for (i = 0; i < il->nsamps; i++) {
86			/* random direction */
87	greg	1.10	h = ilhash(dim, 3) + i;
88	greg	1.11	multisamp(sp, 2, urand(h));
89	greg	1.10	r1 = (dim[1] + sp[0])/nalt;
90	greg	1.13	r2 = (dim[2] + sp[1] - .5)/nazi;
91	greg	1.3	flatdir(dn, r1, r2);
92			for (j = 0; j < 3; j++)
93	greg	1.5	dir[j] = -dn[0]u[j] - dn[1]v[j] - dn[2]*fa->norm[j];
94	greg	1.3	/* random location */
95			do {
96	greg	1.11	multisamp(sp, 2, urand(h+4862+nmisses));
97	greg	1.10	r1 = ur[0] + (ur[1]-ur[0]) * sp[0];
98			r2 = vr[0] + (vr[1]-vr[0]) * sp[1];
99	greg	1.3	for (j = 0; j < 3; j++)
100			org[j] = r1u[j] + r2v[j]
101			+ fa->offset*fa->norm[j];
102			} while (!inface(org, fa) && nmisses++ < MAXMISS);
103			if (nmisses > MAXMISS) {
104			objerror(ob, WARNING, "bad aspect");
105			rt->nrays = 0;
106			freeface(ob);
107			free((char *)distarr);
108			o_default(ob, il, rt, nm);
109			return;
110			}
111			for (j = 0; j < 3; j++)
112			org[j] += .001*fa->norm[j];
113			/* send sample */
114	greg	1.7	raysamp(distarr+3(dim[1]nazi+dim[2]), org, dir, rt);
115	greg	1.3	}
116			rayflush(rt);
117	greg	1.11	/* write out the face and its distribution */
118	greg	1.12	if (average(il, distarr, nalt*nazi)) {
119			if (il->sampdens > 0)
120			flatout(il, distarr, nalt, nazi, u, v, fa->norm);
121			illumout(il, ob);
122	greg	2.2	} else
123	greg	1.12	printobj(il->altmat, ob);
124	greg	1.3	/* clean up */
125			freeface(ob);
126			free((char *)distarr);
127			#undef MAXMISS
128	greg	1.2	}
129
130
131			o_sphere(ob, il, rt, nm) /* make an illum sphere */
132	greg	1.3	register OBJREC *ob;
133	greg	1.2	struct illum_args *il;
134			struct rtproc *rt;
135			char *nm;
136			{
137	greg	1.10	int dim[3];
138	greg	1.2	int n, nalt, nazi;
139			float *distarr;
140	greg	1.10	double sp[4], r1, r2, r3;
141	greg	1.4	FVECT org, dir;
142	greg	1.2	FVECT u, v;
143			register int i, j;
144			/* check arguments */
145			if (ob->oargs.nfargs != 4)
146			objerror(ob, USER, "bad # of arguments");
147			/* set up sampling */
148	greg	1.11	if (il->sampdens <= 0)
149			nalt = nazi = 1;
150			else {
151			n = 4.PI il->sampdens;
152			nalt = sqrt(n/PI) + .5;
153			nazi = PI*nalt + .5;
154			}
155	greg	1.2	n = nalt*nazi;
156			distarr = (float )calloc(n, 3sizeof(float));
157			if (distarr == NULL)
158			error(SYSTEM, "out of memory in o_sphere");
159			dim[0] = random();
160			/* sample sphere */
161			for (dim[1] = 0; dim[1] < nalt; dim[1]++)
162	greg	1.8	for (dim[2] = 0; dim[2] < nazi; dim[2]++)
163	greg	1.2	for (i = 0; i < il->nsamps; i++) {
164	greg	1.10	/* next sample point */
165	greg	1.11	multisamp(sp, 4, urand(ilhash(dim,3)+i));
166	greg	1.2	/* random direction */
167	greg	1.10	r1 = (dim[1] + sp[0])/nalt;
168	greg	1.13	r2 = (dim[2] + sp[1] - .5)/nazi;
169	greg	1.2	rounddir(dir, r1, r2);
170			/* random location */
171	greg	1.8	mkaxes(u, v, dir); /* yuck! */
172	greg	1.10	r3 = sqrt(sp[2]);
173			r2 = 2.PIsp[3];
174	greg	1.5	r1 = r3ob->oargs.farg[3]cos(r2);
175			r2 = r3ob->oargs.farg[3]sin(r2);
176			r3 = ob->oargs.farg[3]sqrt(1.01-r3r3);
177			for (j = 0; j < 3; j++) {
178			org[j] = ob->oargs.farg[j] + r1u[j] + r2v[j] +
179			r3*dir[j];
180			dir[j] = -dir[j];
181			}
182	greg	1.2	/* send sample */
183	greg	1.7	raysamp(distarr+3(dim[1]nazi+dim[2]), org, dir, rt);
184	greg	1.2	}
185			rayflush(rt);
186	greg	1.11	/* write out the sphere and its distribution */
187	greg	1.12	if (average(il, distarr, nalt*nazi)) {
188			if (il->sampdens > 0)
189			roundout(il, distarr, nalt, nazi);
190			else
191			objerror(ob, WARNING, "diffuse distribution");
192			illumout(il, ob);
193	greg	2.2	} else
194	greg	1.12	printobj(il->altmat, ob);
195	greg	1.2	/* clean up */
196			free((char *)distarr);
197			}
198
199
200			o_ring(ob, il, rt, nm) /* make an illum ring */
201			OBJREC *ob;
202			struct illum_args *il;
203			struct rtproc *rt;
204			char *nm;
205			{
206	greg	1.10	int dim[3];
207	greg	1.3	int n, nalt, nazi;
208			float *distarr;
209	greg	1.10	double sp[4], r1, r2, r3;
210	greg	1.4	FVECT dn, org, dir;
211	greg	1.3	FVECT u, v;
212			register CONE *co;
213			register int i, j;
214			/* get/check arguments */
215			co = getcone(ob, 0);
216			/* set up sampling */
217	greg	1.11	if (il->sampdens <= 0)
218			nalt = nazi = 1;
219			else {
220			n = PI * il->sampdens;
221			nalt = sqrt(n/PI) + .5;
222			nazi = PI*nalt + .5;
223			}
224	greg	1.3	n = nalt*nazi;
225			distarr = (float )calloc(n, 3sizeof(float));
226			if (distarr == NULL)
227			error(SYSTEM, "out of memory in o_ring");
228			mkaxes(u, v, co->ad);
229			dim[0] = random();
230			/* sample disk */
231			for (dim[1] = 0; dim[1] < nalt; dim[1]++)
232			for (dim[2] = 0; dim[2] < nazi; dim[2]++)
233			for (i = 0; i < il->nsamps; i++) {
234	greg	1.10	/* next sample point */
235	greg	1.11	multisamp(sp, 4, urand(ilhash(dim,3)+i));
236	greg	1.3	/* random direction */
237	greg	1.10	r1 = (dim[1] + sp[0])/nalt;
238	greg	1.13	r2 = (dim[2] + sp[1] - .5)/nazi;
239	greg	1.3	flatdir(dn, r1, r2);
240			for (j = 0; j < 3; j++)
241	greg	1.5	dir[j] = -dn[0]u[j] - dn[1]v[j] - dn[2]*co->ad[j];
242	greg	1.3	/* random location */
243	greg	1.5	r3 = sqrt(CO_R0(co)*CO_R0(co) +
244	greg	1.10	sp[2](CO_R1(co)CO_R1(co) - CO_R0(co)*CO_R0(co)));
245			r2 = 2.PIsp[3];
246	greg	1.5	r1 = r3*cos(r2);
247			r2 = r3*sin(r2);
248	greg	1.3	for (j = 0; j < 3; j++)
249	greg	1.5	org[j] = CO_P0(co)[j] + r1u[j] + r1v[j] +
250			.001*co->ad[j];
251	greg	1.3
252			/* send sample */
253	greg	1.7	raysamp(distarr+3(dim[1]nazi+dim[2]), org, dir, rt);
254	greg	1.3	}
255			rayflush(rt);
256	greg	1.11	/* write out the ring and its distribution */
257	greg	1.12	if (average(il, distarr, nalt*nazi)) {
258			if (il->sampdens > 0)
259			flatout(il, distarr, nalt, nazi, u, v, co->ad);
260			illumout(il, ob);
261	greg	2.2	} else
262	greg	1.12	printobj(il->altmat, ob);
263	greg	1.3	/* clean up */
264			freecone(ob);
265			free((char *)distarr);
266	greg	1.2	}
267
268
269			raysamp(res, org, dir, rt) /* compute a ray sample */
270			float res[3];
271			FVECT org, dir;
272			register struct rtproc *rt;
273			{
274			register float *fp;
275
276			if (rt->nrays == rt->bsiz)
277			rayflush(rt);
278			rt->dest[rt->nrays] = res;
279			fp = rt->buf + 6*rt->nrays++;
280			fp++ = org[0]; fp++ = org[1]; *fp++ = org[2];
281			fp++ = dir[0]; fp++ = dir[1]; *fp = dir[2];
282			}
283
284
285			rayflush(rt) /* flush buffered rays */
286			register struct rtproc *rt;
287			{
288			register int i;
289
290			if (rt->nrays <= 0)
291			return;
292	greg	1.9	bzero(rt->buf+6rt->nrays, 6sizeof(float));
293	greg	1.14	errno = 0;
294	greg	1.2	if ( process(rt->pd, (char )rt->buf, (char )rt->buf,
295			3sizeof(float)rt->nrays,
296			6sizeof(float)(rt->nrays+1)) <
297			3sizeof(float)rt->nrays )
298			error(SYSTEM, "error reading from rtrace process");
299			i = rt->nrays;
300			while (i--) {
301			rt->dest[i][0] += rt->buf[3*i];
302			rt->dest[i][1] += rt->buf[3*i+1];
303			rt->dest[i][2] += rt->buf[3*i+2];
304			}
305			rt->nrays = 0;
306	greg	1.4	}
307
308
309			mkaxes(u, v, n) /* compute u and v to go with n */
310			FVECT u, v, n;
311			{
312			register int i;
313
314			v[0] = v[1] = v[2] = 0.0;
315			for (i = 0; i < 3; i++)
316			if (n[i] < 0.6 && n[i] > -0.6)
317			break;
318			v[i] = 1.0;
319			fcross(u, v, n);
320			normalize(u);
321			fcross(v, n, u);
322			}
323
324
325			rounddir(dv, alt, azi) /* compute uniform spherical direction */
326			register FVECT dv;
327			double alt, azi;
328			{
329			double d1, d2;
330
331			dv[2] = 1. - 2.*alt;
332			d1 = sqrt(1. - dv[2]*dv[2]);
333			d2 = 2.PI azi;
334			dv[0] = d1*cos(d2);
335			dv[1] = d1*sin(d2);
336			}
337
338
339			flatdir(dv, alt, azi) /* compute uniform hemispherical direction */
340			register FVECT dv;
341			double alt, azi;
342			{
343			double d1, d2;
344
345			d1 = sqrt(alt);
346			d2 = 2.PI azi;
347			dv[0] = d1*cos(d2);
348			dv[1] = d1*sin(d2);
349	greg	1.6	dv[2] = sqrt(1. - alt);
350	greg	1.1	}