src/rt/func.c

#ifndef lint
static const char       RCSid[] = "$Id: func.c,v 2.26 2012/06/09 07:16:47 greg Exp $";
#endif
/*
 *  func.c - interface to calcomp functions.
 */

#include "copyright.h"

#include  "ray.h"
#include  "paths.h"
#include  "otypes.h"
#include  "func.h"


#define  INITFILE       "rayinit.cal"
#define  CALSUF         ".cal"
#define  LCALSUF        4
char  REFVNAME[] = "`FILE_REFCNT";

XF  unitxf = {                  /* identity transform */
        {{1.0, 0.0, 0.0, 0.0},
        {0.0, 1.0, 0.0, 0.0},
        {0.0, 0.0, 1.0, 0.0},
        {0.0, 0.0, 0.0, 1.0}},
        1.0
};

XF  funcxf;                     /* current transformation */
static OBJREC  *fobj = NULL;    /* current function object */
static RAY  *fray = NULL;       /* current function ray */

static char  rayinitcal[] = INITFILE;

static double  l_erf(char *), l_erfc(char *), l_arg(char *);


void
initfunc()      /* initialize function evaluation */
{
        if (!rayinitcal[0])     /* already done? */
                return;
        esupport |= E_VARIABLE|E_FUNCTION|E_INCHAN|E_RCONST|E_REDEFW;
        esupport &= ~(E_OUTCHAN);
        setcontext("");
        scompile("Dx=$1;Dy=$2;Dz=$3;", NULL, 0);
        scompile("Nx=$4;Ny=$5;Nz=$6;", NULL, 0);
        scompile("Px=$7;Py=$8;Pz=$9;", NULL, 0);
        scompile("T=$10;Ts=$25;Rdot=$11;", NULL, 0);
        scompile("S=$12;Tx=$13;Ty=$14;Tz=$15;", NULL, 0);
        scompile("Ix=$16;Iy=$17;Iz=$18;", NULL, 0);
        scompile("Jx=$19;Jy=$20;Jz=$21;", NULL, 0);
        scompile("Kx=$22;Ky=$23;Kz=$24;", NULL, 0);
        scompile("Lu=$26;Lv=$27;", NULL, 0);
        funset("arg", 1, '=', l_arg);
        funset("erf", 1, ':', l_erf);
        funset("erfc", 1, ':', l_erfc);
        setnoisefuncs();
        setprismfuncs();
        loadfunc(rayinitcal);
        rayinitcal[0] = '\0';
}


MFUNC *
getfunc(        /* get function for this modifier */
        OBJREC  *m,
        int  ff,
        unsigned int  ef,
        int  dofwd
)
{
        char  sbuf[MAXSTR];
        char  **arg;
        MFUNC  *f;
        int  ne, na;
        int  i;
                                        /* check to see if done already */
        if ((f = (MFUNC *)m->os) != NULL)
                return(f);
        fobj = NULL; fray = NULL;
        if (rayinitcal[0])              /* initialize on first call */
                initfunc();
        if ((na = m->oargs.nsargs) <= ff)
                goto toofew;
        arg = m->oargs.sarg;
        if ((f = (MFUNC *)calloc(1, sizeof(MFUNC))) == NULL)
                goto memerr;
        i = strlen(arg[ff]);                    /* set up context */
        if (i == 1 && arg[ff][0] == '.') {
                setcontext(f->ctx = "");        /* "." means no file */
        } else {
                strcpy(sbuf,arg[ff]);           /* file name is context */
                if (i > LCALSUF && !strcmp(sbuf+i-LCALSUF, CALSUF))
                        sbuf[i-LCALSUF] = '\0'; /* remove suffix */
                setcontext(f->ctx = savestr(sbuf));
                if (!vardefined(REFVNAME)) {    /* file loaded? */
                        loadfunc(arg[ff]);
                        varset(REFVNAME, '=', 1.0);
                } else                          /* reference_count++ */
                        varset(REFVNAME, '=', varvalue(REFVNAME)+1.0);
        }
        curfunc = NULL;                 /* parse expressions */
        sprintf(sbuf, "%s \"%s\"", ofun[m->otype].funame, m->oname);
        for (i=0, ne=0; ef && i < na; i++, ef>>=1)
                if (ef & 1) {                   /* flagged as an expression? */
                        if (ne >= MAXEXPR)
                                objerror(m, INTERNAL, "too many expressions");
                        initstr(arg[i], sbuf, 0);
                        f->ep[ne++] = getE1();
                        if (nextc != EOF)
                                syntax("unexpected character");
                }
        if (ef)
                goto toofew;
        if (i <= ff)                    /* find transform args */
                i = ff+1;
        while (i < na && arg[i][0] != '-')
                i++;
        if (i == na) {                  /* no transform */
                f->fxp = f->bxp = &unitxf;
        } else {                        /* get transform */
                if ((f->bxp = (XF *)malloc(sizeof(XF))) == NULL)
                        goto memerr;
                if (invxf(f->bxp, na-i, arg+i) != na-i)
                        objerror(m, USER, "bad transform");
                if (f->bxp->sca < 0.0)
                        f->bxp->sca = -f->bxp->sca;
                if (dofwd) {                    /* do both transforms */
                        if ((f->fxp = (XF *)malloc(sizeof(XF))) == NULL)
                                goto memerr;
                        xf(f->fxp, na-i, arg+i);
                        if (f->fxp->sca < 0.0)
                                f->fxp->sca = -f->fxp->sca;
                }
        }
        m->os = (char *)f;
        return(f);
toofew:
        objerror(m, USER, "too few string arguments");
memerr:
        error(SYSTEM, "out of memory in getfunc");
        return NULL; /* pro forma return */
}


void
freefunc(                       /* free memory associated with modifier */
        OBJREC  *m
)
{
        MFUNC  *f;
        int  i;

        if ((f = (MFUNC *)m->os) == NULL)
                return;
        for (i = 0; f->ep[i] != NULL; i++)
                epfree(f->ep[i]);
        if (f->ctx[0]) {                        /* done with definitions */
                setcontext(f->ctx);
                i = varvalue(REFVNAME)-.5;      /* reference_count-- */
                if (i > 0)
                        varset(REFVNAME, '=', (double)i);
                else
                        dcleanup(2);            /* remove definitions */
                freestr(f->ctx);
        }
        if (f->bxp != &unitxf)
                free((void *)f->bxp);
        if ((f->fxp != NULL) & (f->fxp != &unitxf))
                free((void *)f->fxp);
        free((void *)f);
        m->os = NULL;
}


int
setfunc(                        /* set channels for function call */
        OBJREC  *m,
        RAY     *r
)
{
        static RNUMBER  lastrno = ~0;
        MFUNC           *f;
                                        /* get function if any */
        if ((f = (MFUNC *)m->os) == NULL)
                objerror(m, CONSISTENCY, "setfunc called before getfunc");
                
        setcontext(f->ctx);             /* set evaluator context */
                                        /* check to see if matrix set */
        if ((m == fobj) & (r->rno == lastrno))
                return(0);
        fobj = m;
        fray = r;
        if (r->rox != NULL) {
                if (f->bxp != &unitxf) {
                        funcxf.sca = r->rox->b.sca * f->bxp->sca;
                        multmat4(funcxf.xfm, r->rox->b.xfm, f->bxp->xfm);
                } else
                        funcxf = r->rox->b;
        } else
                funcxf = *f->bxp;
        lastrno = r->rno;
        eclock++;               /* notify expression evaluator */
        return(1);
}


int
worldfunc(                      /* special function context sans object */
        char    *ctx,
        RAY     *r
)
{
        static RNUMBER  lastrno = ~0;

        if (rayinitcal[0])              /* initialize on first call */
                initfunc();
                                        /* set evaluator context */
        setcontext(ctx);
                                        /* check if ray already set */
        if ((fobj == NULL) & (r->rno == lastrno))
                return(0);
        fobj = NULL;
        fray = r;
        funcxf = unitxf;
        lastrno = r->rno;
        eclock++;               /* notify expression evaluator */
        return(1);
}


void
loadfunc(                       /* load definition file */
        char  *fname
)
{
        char  *ffname;

        if ((ffname = getpath(fname, getrlibpath(), R_OK)) == NULL) {
                sprintf(errmsg, "cannot find function file \"%s\"", fname);
                error(USER, errmsg);
        }
        fcompile(ffname);
}


static double
l_arg(char *nm)                 /* return nth real argument */
{
        int  n;

        if (fobj == NULL)
                error(USER, "arg(n) called without a context");

        n = argument(1) + .5;           /* round to integer */

        if (n < 1)
                return(fobj->oargs.nfargs);

        if (n > fobj->oargs.nfargs) {
                sprintf(errmsg, "missing real argument %d", n);
                objerror(fobj, USER, errmsg);
        }
        return(fobj->oargs.farg[n-1]);
}


static double
l_erf(char *nm)                 /* error function */
{
        return(erf(argument(1)));
}


static double
l_erfc(char *nm)                /* cumulative error function */
{
        return(erfc(argument(1)));
}


double
chanvalue(                      /* return channel n to calcomp */
        int  n
)
{
        if (fray == NULL)
                syntax("ray parameter used in constant expression");

        if (--n < 0)
                goto badchan;

        if (n <= 2)                     /* ray direction */

                return( (       fray->rdir[0]*funcxf.xfm[0][n] +
                                fray->rdir[1]*funcxf.xfm[1][n] +
                                fray->rdir[2]*funcxf.xfm[2][n]  )
                         / funcxf.sca );

        if (n <= 5)                     /* surface normal */

                return( (       fray->ron[0]*funcxf.xfm[0][n-3] +
                                fray->ron[1]*funcxf.xfm[1][n-3] +
                                fray->ron[2]*funcxf.xfm[2][n-3] )
                         / funcxf.sca );

        if (n <= 8)                     /* intersection */

                return( fray->rop[0]*funcxf.xfm[0][n-6] +
                                fray->rop[1]*funcxf.xfm[1][n-6] +
                                fray->rop[2]*funcxf.xfm[2][n-6] +
                                             funcxf.xfm[3][n-6] );

        if (n == 9)                     /* total distance */
                return(raydist(fray,PRIMARY) * funcxf.sca);

        if (n == 10)                    /* dot product (range [-1,1]) */
                return( fray->rod <= -1.0 ? -1.0 :
                        fray->rod >= 1.0 ? 1.0 :
                        fray->rod );

        if (n == 11)                    /* scale */
                return(funcxf.sca);

        if (n <= 14)                    /* origin */
                return(funcxf.xfm[3][n-12]);

        if (n <= 17)                    /* i unit vector */
                return(funcxf.xfm[0][n-15] / funcxf.sca);

        if (n <= 20)                    /* j unit vector */
                return(funcxf.xfm[1][n-18] / funcxf.sca);

        if (n <= 23)                    /* k unit vector */
                return(funcxf.xfm[2][n-21] / funcxf.sca);

        if (n == 24)                    /* single ray (shadow) distance */
                return((fray->rot+raydist(fray->parent,SHADOW)) * funcxf.sca);

        if (n <= 26)                    /* local (u,v) coordinates */
                return(fray->uv[n-25]);
badchan:
        error(USER, "illegal channel number");
        return(0.0);
}
Revision:	2.27
Committed:	Wed Jun 27 16:29:26 2012 UTC (11 years, 10 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad4R2P2, rad4R2, rad4R2P1
Changes since 2.26:	+4 -1 lines
Log Message:	Added missing initialization call
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.27	static const char RCSid[] = "$Id: func.c,v 2.26 2012/06/09 07:16:47 greg Exp $";
3	greg	1.1	#endif
4			/*
5			* func.c - interface to calcomp functions.
6	greg	2.14	*/
7
8	greg	2.15	#include "copyright.h"
9	greg	1.1
10			#include "ray.h"
11	greg	2.21	#include "paths.h"
12	greg	1.1	#include "otypes.h"
13	greg	2.2	#include "func.h"
14	greg	1.1
15	greg	2.2
16	greg	1.21	#define INITFILE "rayinit.cal"
17	greg	2.2	#define CALSUF ".cal"
18			#define LCALSUF 4
19	greg	2.10	char REFVNAME[] = "`FILE_REFCNT";
20	greg	1.21
21	greg	1.13	XF unitxf = { /* identity transform */
22	greg	2.8	{{1.0, 0.0, 0.0, 0.0},
23			{0.0, 1.0, 0.0, 0.0},
24			{0.0, 0.0, 1.0, 0.0},
25			{0.0, 0.0, 0.0, 1.0}},
26	greg	1.13	1.0
27			};
28
29	greg	1.12	XF funcxf; /* current transformation */
30			static OBJREC fobj = NULL; / current function object */
31			static RAY fray = NULL; / current function ray */
32	greg	1.1
33	greg	2.26	static char rayinitcal[] = INITFILE;
34
35	greg	2.20	static double l_erf(char ), l_erfc(char ), l_arg(char *);
36	greg	1.1
37	greg	2.2
38	greg	2.26	void
39			initfunc() /* initialize function evaluation */
40			{
41			if (!rayinitcal[0]) /* already done? */
42			return;
43			esupport \|= E_VARIABLE\|E_FUNCTION\|E_INCHAN\|E_RCONST\|E_REDEFW;
44			esupport &= ~(E_OUTCHAN);
45			setcontext("");
46			scompile("Dx=$1;Dy=$2;Dz=$3;", NULL, 0);
47			scompile("Nx=$4;Ny=$5;Nz=$6;", NULL, 0);
48			scompile("Px=$7;Py=$8;Pz=$9;", NULL, 0);
49			scompile("T=$10;Ts=$25;Rdot=$11;", NULL, 0);
50			scompile("S=$12;Tx=$13;Ty=$14;Tz=$15;", NULL, 0);
51			scompile("Ix=$16;Iy=$17;Iz=$18;", NULL, 0);
52			scompile("Jx=$19;Jy=$20;Jz=$21;", NULL, 0);
53			scompile("Kx=$22;Ky=$23;Kz=$24;", NULL, 0);
54			scompile("Lu=$26;Lv=$27;", NULL, 0);
55			funset("arg", 1, '=', l_arg);
56			funset("erf", 1, ':', l_erf);
57			funset("erfc", 1, ':', l_erfc);
58			setnoisefuncs();
59			setprismfuncs();
60			loadfunc(rayinitcal);
61			rayinitcal[0] = '\0';
62			}
63
64
65	greg	2.25	MFUNC *
66	schorsch	2.22	getfunc( /* get function for this modifier */
67			OBJREC *m,
68			int ff,
69			unsigned int ef,
70			int dofwd
71			)
72	greg	2.2	{
73			char sbuf[MAXSTR];
74	greg	2.25	char **arg;
75			MFUNC *f;
76	greg	2.2	int ne, na;
77	greg	2.25	int i;
78	greg	2.2	/* check to see if done already */
79			if ((f = (MFUNC *)m->os) != NULL)
80			return(f);
81	greg	2.7	fobj = NULL; fray = NULL;
82	greg	2.26	if (rayinitcal[0]) /* initialize on first call */
83			initfunc();
84	greg	2.2	if ((na = m->oargs.nsargs) <= ff)
85			goto toofew;
86			arg = m->oargs.sarg;
87			if ((f = (MFUNC *)calloc(1, sizeof(MFUNC))) == NULL)
88			goto memerr;
89			i = strlen(arg[ff]); /* set up context */
90	greg	2.26	if (i == 1 && arg[ff][0] == '.') {
91	greg	2.2	setcontext(f->ctx = ""); /* "." means no file */
92	greg	2.26	} else {
93	greg	2.14	strcpy(sbuf,arg[ff]); /* file name is context */
94	greg	2.2	if (i > LCALSUF && !strcmp(sbuf+i-LCALSUF, CALSUF))
95			sbuf[i-LCALSUF] = '\0'; /* remove suffix */
96			setcontext(f->ctx = savestr(sbuf));
97			if (!vardefined(REFVNAME)) { /* file loaded? */
98	greg	2.5	loadfunc(arg[ff]);
99	greg	2.2	varset(REFVNAME, '=', 1.0);
100			} else /* reference_count++ */
101			varset(REFVNAME, '=', varvalue(REFVNAME)+1.0);
102			}
103			curfunc = NULL; /* parse expressions */
104			sprintf(sbuf, "%s \"%s\"", ofun[m->otype].funame, m->oname);
105			for (i=0, ne=0; ef && i < na; i++, ef>>=1)
106			if (ef & 1) { /* flagged as an expression? */
107			if (ne >= MAXEXPR)
108			objerror(m, INTERNAL, "too many expressions");
109			initstr(arg[i], sbuf, 0);
110			f->ep[ne++] = getE1();
111			if (nextc != EOF)
112			syntax("unexpected character");
113			}
114			if (ef)
115			goto toofew;
116			if (i <= ff) /* find transform args */
117			i = ff+1;
118			while (i < na && arg[i][0] != '-')
119			i++;
120	greg	2.26	if (i == na) { /* no transform */
121			f->fxp = f->bxp = &unitxf;
122			} else { /* get transform */
123			if ((f->bxp = (XF *)malloc(sizeof(XF))) == NULL)
124	greg	2.3	goto memerr;
125	greg	2.26	if (invxf(f->bxp, na-i, arg+i) != na-i)
126	greg	2.2	objerror(m, USER, "bad transform");
127	greg	2.26	if (f->bxp->sca < 0.0)
128			f->bxp->sca = -f->bxp->sca;
129	greg	2.2	if (dofwd) { /* do both transforms */
130	greg	2.26	if ((f->fxp = (XF *)malloc(sizeof(XF))) == NULL)
131	greg	2.3	goto memerr;
132	greg	2.26	xf(f->fxp, na-i, arg+i);
133			if (f->fxp->sca < 0.0)
134			f->fxp->sca = -f->fxp->sca;
135	greg	2.2	}
136			}
137			m->os = (char *)f;
138			return(f);
139			toofew:
140	greg	2.4	objerror(m, USER, "too few string arguments");
141	greg	2.2	memerr:
142			error(SYSTEM, "out of memory in getfunc");
143	schorsch	2.22	return NULL; /* pro forma return */
144	greg	2.2	}
145
146
147	greg	2.25	void
148	schorsch	2.22	freefunc( /* free memory associated with modifier */
149			OBJREC *m
150			)
151	greg	2.2	{
152	greg	2.25	MFUNC *f;
153			int i;
154	greg	2.2
155			if ((f = (MFUNC *)m->os) == NULL)
156			return;
157			for (i = 0; f->ep[i] != NULL; i++)
158			epfree(f->ep[i]);
159			if (f->ctx[0]) { /* done with definitions */
160			setcontext(f->ctx);
161			i = varvalue(REFVNAME)-.5; /* reference_count-- */
162			if (i > 0)
163			varset(REFVNAME, '=', (double)i);
164			else
165			dcleanup(2); /* remove definitions */
166			freestr(f->ctx);
167			}
168	greg	2.26	if (f->bxp != &unitxf)
169			free((void *)f->bxp);
170			if ((f->fxp != NULL) & (f->fxp != &unitxf))
171			free((void *)f->fxp);
172	greg	2.14	free((void *)f);
173	greg	2.2	m->os = NULL;
174			}
175
176
177	greg	2.25	int
178	schorsch	2.22	setfunc( /* set channels for function call */
179	greg	2.26	OBJREC *m,
180			RAY *r
181	schorsch	2.22	)
182	greg	1.1	{
183	greg	2.26	static RNUMBER lastrno = ~0;
184			MFUNC *f;
185	greg	2.25	/* get function if any */
186	greg	2.26	if ((f = (MFUNC *)m->os) == NULL)
187			objerror(m, CONSISTENCY, "setfunc called before getfunc");
188
189			setcontext(f->ctx); /* set evaluator context */
190	greg	2.2	/* check to see if matrix set */
191	greg	2.25	if ((m == fobj) & (r->rno == lastrno))
192	greg	1.17	return(0);
193	greg	1.1	fobj = m;
194			fray = r;
195	greg	2.26	if (r->rox != NULL) {
196			if (f->bxp != &unitxf) {
197			funcxf.sca = r->rox->b.sca * f->bxp->sca;
198			multmat4(funcxf.xfm, r->rox->b.xfm, f->bxp->xfm);
199	greg	1.13	} else
200	schorsch	2.19	funcxf = r->rox->b;
201	greg	2.26	} else
202			funcxf = *f->bxp;
203			lastrno = r->rno;
204			eclock++; /* notify expression evaluator */
205			return(1);
206			}
207
208
209			int
210			worldfunc( /* special function context sans object */
211			char *ctx,
212			RAY *r
213			)
214			{
215			static RNUMBER lastrno = ~0;
216	greg	2.27
217			if (rayinitcal[0]) /* initialize on first call */
218			initfunc();
219	greg	2.26	/* set evaluator context */
220			setcontext(ctx);
221			/* check if ray already set */
222			if ((fobj == NULL) & (r->rno == lastrno))
223			return(0);
224			fobj = NULL;
225			fray = r;
226			funcxf = unitxf;
227	greg	1.16	lastrno = r->rno;
228	greg	1.1	eclock++; /* notify expression evaluator */
229	greg	1.17	return(1);
230	greg	1.1	}
231
232
233	greg	2.25	void
234	schorsch	2.22	loadfunc( /* load definition file */
235			char *fname
236			)
237	greg	1.1	{
238			char *ffname;
239
240	greg	2.18	if ((ffname = getpath(fname, getrlibpath(), R_OK)) == NULL) {
241	greg	1.1	sprintf(errmsg, "cannot find function file \"%s\"", fname);
242			error(USER, errmsg);
243			}
244			fcompile(ffname);
245			}
246
247
248	greg	2.2	static double
249	greg	2.20	l_arg(char nm) / return nth real argument */
250	greg	1.1	{
251	greg	2.25	int n;
252	greg	1.1
253	greg	2.7	if (fobj == NULL)
254	greg	2.25	error(USER, "arg(n) called without a context");
255	greg	2.7
256	greg	1.1	n = argument(1) + .5; /* round to integer */
257
258			if (n < 1)
259			return(fobj->oargs.nfargs);
260
261			if (n > fobj->oargs.nfargs) {
262			sprintf(errmsg, "missing real argument %d", n);
263			objerror(fobj, USER, errmsg);
264			}
265			return(fobj->oargs.farg[n-1]);
266	greg	1.19	}
267
268
269	greg	2.2	static double
270	greg	2.20	l_erf(char nm) / error function */
271	greg	1.19	{
272			return(erf(argument(1)));
273			}
274
275
276	greg	2.2	static double
277	greg	2.20	l_erfc(char nm) / cumulative error function */
278	greg	1.19	{
279			return(erfc(argument(1)));
280	greg	1.1	}
281
282
283	greg	2.25	double
284	schorsch	2.22	chanvalue( /* return channel n to calcomp */
285	greg	2.25	int n
286	schorsch	2.22	)
287	greg	1.1	{
288	greg	2.7	if (fray == NULL)
289			syntax("ray parameter used in constant expression");
290	greg	1.1
291	greg	1.10	if (--n < 0)
292			goto badchan;
293	greg	1.1
294	greg	2.17	if (n <= 2) /* ray direction */
295	greg	1.1
296	greg	1.12	return( ( fray->rdir[0]*funcxf.xfm[0][n] +
297			fray->rdir[1]*funcxf.xfm[1][n] +
298			fray->rdir[2]*funcxf.xfm[2][n] )
299			/ funcxf.sca );
300	greg	1.1
301	greg	2.17	if (n <= 5) /* surface normal */
302	greg	1.8
303	greg	1.12	return( ( fray->ron[0]*funcxf.xfm[0][n-3] +
304			fray->ron[1]*funcxf.xfm[1][n-3] +
305			fray->ron[2]*funcxf.xfm[2][n-3] )
306			/ funcxf.sca );
307	greg	1.8
308	greg	2.17	if (n <= 8) /* intersection */
309	greg	1.8
310	greg	1.12	return( fray->rop[0]*funcxf.xfm[0][n-6] +
311			fray->rop[1]*funcxf.xfm[1][n-6] +
312			fray->rop[2]*funcxf.xfm[2][n-6] +
313			funcxf.xfm[3][n-6] );
314	greg	1.8
315	greg	2.13	if (n == 9) /* total distance */
316			return(raydist(fray,PRIMARY) * funcxf.sca);
317	greg	1.10
318	greg	1.18	if (n == 10) /* dot product (range [-1,1]) */
319			return( fray->rod <= -1.0 ? -1.0 :
320			fray->rod >= 1.0 ? 1.0 :
321			fray->rod );
322	greg	1.10
323	greg	1.8	if (n == 11) /* scale */
324	greg	1.12	return(funcxf.sca);
325	greg	1.8
326	greg	2.17	if (n <= 14) /* origin */
327	greg	1.12	return(funcxf.xfm[3][n-12]);
328	greg	1.8
329	greg	2.17	if (n <= 17) /* i unit vector */
330	greg	1.12	return(funcxf.xfm[0][n-15] / funcxf.sca);
331	greg	1.8
332	greg	2.17	if (n <= 20) /* j unit vector */
333			return(funcxf.xfm[1][n-18] / funcxf.sca);
334	greg	1.8
335	greg	2.17	if (n <= 23) /* k unit vector */
336	greg	1.12	return(funcxf.xfm[2][n-21] / funcxf.sca);
337	greg	2.6
338	greg	2.17	if (n == 24) /* single ray (shadow) distance */
339	greg	2.13	return((fray->rot+raydist(fray->parent,SHADOW)) * funcxf.sca);
340	greg	2.16
341	greg	2.17	if (n <= 26) /* local (u,v) coordinates */
342			return(fray->uv[n-25]);
343	greg	1.10	badchan:
344			error(USER, "illegal channel number");
345	greg	2.16	return(0.0);
346	greg	1.1	}