src/rt/raytrace.c

/* Copyright (c) 1986 Regents of the University of California */

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

/*
 *  raytrace.c - routines for tracing and shading rays.
 *
 *     8/7/85
 */

#include  "ray.h"

#include  "octree.h"

#include  "otypes.h"

extern CUBE  thescene;                  /* our scene */
extern int  maxdepth;                   /* maximum recursion depth */
extern double  minweight;               /* minimum ray weight */

long  nrays = 0L;                       /* number of rays traced */

#define  MAXLOOP        1024            /* modifier loop detection */

#define  RAYHIT         (-1)            /* return value for intercepted ray */


rayorigin(r, ro, rt, rw)                /* start new ray from old one */
register RAY  *r, *ro;
int  rt;
double  rw;
{
        if ((r->parent = ro) == NULL) {         /* primary ray */
                r->rlvl = 0;
                r->rweight = rw;
                r->crtype = r->rtype = rt;
                r->rsrc = -1;
                r->clipset = NULL;
        } else {                                /* spawned ray */
                r->rlvl = ro->rlvl;
                if (rt & RAYREFL) {
                        r->rlvl++;
                        r->rsrc = -1;
                        r->clipset = ro->clipset;
                } else {
                        r->rsrc = ro->rsrc;
                        r->clipset = ro->newcset;
                }
                r->rweight = ro->rweight * rw;
                r->crtype = ro->crtype | (r->rtype = rt);
                VCOPY(r->rorg, ro->rop);
        }
        r->rno = nrays;
        r->newcset = r->clipset;
        r->ro = NULL;
        r->rot = FHUGE;
        r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
        setcolor(r->pcol, 1.0, 1.0, 1.0);
        setcolor(r->rcol, 0.0, 0.0, 0.0);
        return(r->rlvl <= maxdepth && r->rweight >= minweight ? 0 : -1);
}


rayvalue(r)                     /* compute a ray's value */
register RAY  *r;
{
        extern int  (*trace)();

        if (localhit(r, &thescene) || sourcehit(r))
                rayshade(r, r->ro->omod);

        if (trace != NULL)
                (*trace)(r);            /* trace execution */
}


raytrans(r)                     /* transmit ray as is */
RAY  *r;
{
        RAY  tr;

        if (rayorigin(&tr, r, TRANS, 1.0) == 0) {
                VCOPY(tr.rdir, r->rdir);
                rayvalue(&tr);
                copycolor(r->rcol, tr.rcol);
        }
}


rayshade(r, mod)                /* shade ray r with material mod */
register RAY  *r;
int  mod;
{
        static int  depth = 0;
        register OBJREC  *m;
                                        /* check for clipped surface */
        if (r->clipset != NULL && r->rot < FHUGE &&
                        inset(r->clipset, mod)) {
                raytrans(r);
                return;
        }
                                        /* check for infinite loop */
        if (depth++ >= MAXLOOP)
                objerror(r->ro, USER, "possible modifier loop");
        for ( ; mod != OVOID; mod = m->omod) {
                m = objptr(mod);
                /****** unnecessary test since modifier() is always called
                if (!ismodifier(m->otype)) {
                        sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
                        error(USER, errmsg);
                }
                ******/
                (*ofun[m->otype].funp)(m, r);   /* execute function */
                m->lastrno = r->rno;
                if (ismaterial(m->otype)) {     /* materials call raytexture */
                        depth--;
                        return;         /* we're done */
                }
        }
        objerror(r->ro, USER, "material not found");
}


raytexture(r, mod)                      /* get material modifiers */
RAY  *r;
int  mod;
{
        static int  depth = 0;
        register OBJREC  *m;
                                        /* check for infinite loop */
        if (depth++ >= MAXLOOP)
                objerror(r->ro, USER, "modifier loop");
                                        /* execute textures and patterns */
        for ( ; mod != OVOID; mod = m->omod) {
                m = objptr(mod);
                if (!istexture(m->otype)) {
                        sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
                        error(USER, errmsg);
                }
                (*ofun[m->otype].funp)(m, r);
                m->lastrno = r->rno;
        }
        depth--;                        /* end here */
}


raymixture(r, fore, back, coef)         /* mix modifiers */
register RAY  *r;
OBJECT  fore, back;
double  coef;
{
        FVECT  curpert, forepert, backpert;
        COLOR  curpcol, forepcol, backpcol;
        register int  i;
                                        /* clip coefficient */
        if (coef > 1.0)
                coef = 1.0;
        else if (coef < 0.0)
                coef = 0.0;
                                        /* save current mods */
        VCOPY(curpert, r->pert);
        copycolor(curpcol, r->pcol);
                                        /* compute new mods */
                                                /* foreground */
        r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
        setcolor(r->pcol, 1.0, 1.0, 1.0);
        if (fore != OVOID && coef > FTINY)
                raytexture(r, fore);
        VCOPY(forepert, r->pert);
        copycolor(forepcol, r->pcol);
                                                /* background */
        r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
        setcolor(r->pcol, 1.0, 1.0, 1.0);
        if (back != OVOID && coef < 1.0-FTINY)
                raytexture(r, back);
        VCOPY(backpert, r->pert);
        copycolor(backpcol, r->pcol);
                                        /* sum perturbations */
        for (i = 0; i < 3; i++)
                r->pert[i] = curpert[i] + coef*forepert[i] +
                                (1.0-coef)*backpert[i];
                                        /* multiply colors */
        setcolor(r->pcol, coef*colval(forepcol,RED) +
                                (1.0-coef)*colval(backpcol,RED),
                        coef*colval(forepcol,GRN) +
                                (1.0-coef)*colval(backpcol,GRN),
                        coef*colval(forepcol,BLU) +
                                (1.0-coef)*colval(backpcol,BLU));
        multcolor(r->pcol, curpcol);
}


double
raynormal(norm, r)              /* compute perturbed normal for ray */
FVECT  norm;
register RAY  *r;
{
        double  newdot;
        register int  i;

        /*      The perturbation is added to the surface normal to obtain
         *  the new normal.  If the new normal would affect the surface
         *  orientation wrt. the ray, a correction is made.  The method is
         *  still fraught with problems since reflected rays and similar
         *  directions calculated from the surface normal may spawn rays behind
         *  the surface.  The only solution is to curb textures at high
         *  incidence (Rdot << 1).
         */

        for (i = 0; i < 3; i++)
                norm[i] = r->ron[i] + r->pert[i];

        if (normalize(norm) == 0.0) {
                objerror(r->ro, WARNING, "illegal normal perturbation");
                VCOPY(norm, r->ron);
                return(r->rod);
        }
        newdot = -DOT(norm, r->rdir);
        if ((newdot > 0.0) != (r->rod > 0.0)) {         /* fix orientation */
                for (i = 0; i < 3; i++)
                        norm[i] += 2.0*newdot*r->rdir[i];
                newdot = -newdot;
        }
        return(newdot);
}


flipsurface(r)                  /* reverse surface orientation */
register RAY  *r;
{
        r->rod = -r->rod;
        r->ron[0] = -r->ron[0];
        r->ron[1] = -r->ron[1];
        r->ron[2] = -r->ron[2];
        r->pert[0] = -r->pert[0];
        r->pert[1] = -r->pert[1];
        r->pert[2] = -r->pert[2];
}


localhit(r, scene)              /* check for hit in the octree */
register RAY  *r;
register CUBE  *scene;
{
        FVECT  curpos;                  /* current cube position */
        int  mpos, mneg;                /* sign flags */
        double  t, dt;
        register int  i;

        nrays++;                        /* increment trace counter */

        mpos = mneg = 0;
        for (i = 0; i < 3; i++) {
                curpos[i] = r->rorg[i];
                if (r->rdir[i] > FTINY)
                        mpos |= 1 << i;
                else if (r->rdir[i] < -FTINY)
                        mneg |= 1 << i;
        }
        t = 0.0;
        if (!incube(scene, curpos)) {
                                        /* find distance to entry */
                for (i = 0; i < 3; i++) {
                                        /* plane in our direction */
                        if (mpos & 1<<i)
                                dt = scene->cuorg[i];
                        else if (mneg & 1<<i)
                                dt = scene->cuorg[i] + scene->cusize;
                        else
                                continue;
                                        /* distance to the plane */
                        dt = (dt - r->rorg[i])/r->rdir[i];
                        if (dt > t)
                                t = dt; /* farthest face is the one */
                }
                t += FTINY;             /* fudge to get inside cube */
                                        /* advance position */
                for (i = 0; i < 3; i++)
                        curpos[i] += r->rdir[i]*t;

                if (!incube(scene, curpos))     /* non-intersecting ray */
                        return(0);
        }
        return(raymove(curpos, mpos, mneg, r, scene) == RAYHIT);
}


static int
raymove(pos, plus, minus, r, cu)        /* check for hit as we move */
FVECT  pos;                     /* modified */
int  plus, minus;               /* direction indicators to speed tests */
register RAY  *r;
register CUBE  *cu;
{
        int  ax;
        double  dt, t;
        register int  sgn;

        if (istree(cu->cutree)) {               /* recurse on subcubes */
                CUBE  cukid;
                register int  br;

                cukid.cusize = cu->cusize * 0.5;        /* find subcube */
                VCOPY(cukid.cuorg, cu->cuorg);
                br = 0;
                if (pos[0] >= cukid.cuorg[0]+cukid.cusize) {
                        cukid.cuorg[0] += cukid.cusize;
                        br |= 1;
                }
                if (pos[1] >= cukid.cuorg[1]+cukid.cusize) {
                        cukid.cuorg[1] += cukid.cusize;
                        br |= 2;
                }
                if (pos[2] >= cukid.cuorg[2]+cukid.cusize) {
                        cukid.cuorg[2] += cukid.cusize;
                        br |= 4;
                }
                for ( ; ; ) {
                        cukid.cutree = octkid(cu->cutree, br);
                        if ((ax = raymove(pos,plus,minus,r,&cukid)) == RAYHIT)
                                return(RAYHIT);
                        sgn = 1 << ax;
                        if (sgn & minus)                /* negative axis? */
                                if (sgn & br) {
                                        cukid.cuorg[ax] -= cukid.cusize;
                                        br &= ~sgn;
                                } else
                                        return(ax);     /* underflow */
                        else
                                if (sgn & br)
                                        return(ax);     /* overflow */
                                else {
                                        cukid.cuorg[ax] += cukid.cusize;
                                        br |= sgn;
                                }
                }
                /*NOTREACHED*/
        }
        if (isfull(cu->cutree) && checkhit(r, cu))
                return(RAYHIT);
                                        /* advance to next cube */
        sgn = plus | minus;
        if (sgn&1) {
                dt = plus&1 ? cu->cuorg[0] + cu->cusize : cu->cuorg[0];
                t = (dt - pos[0])/r->rdir[0];
                ax = 0;
        } else
                t = FHUGE;
        if (sgn&2) {
                dt = plus&2 ? cu->cuorg[1] + cu->cusize : cu->cuorg[1];
                dt = (dt - pos[1])/r->rdir[1];
                if (dt < t) {
                        t = dt;
                        ax = 1;
                }
        }
        if (sgn&4) {
                dt = plus&4 ? cu->cuorg[2] + cu->cusize : cu->cuorg[2];
                dt = (dt - pos[2])/r->rdir[2];
                if (dt < t) {
                        t = dt;
                        ax = 2;
                }
        }
        pos[0] += r->rdir[0]*t;
        pos[1] += r->rdir[1]*t;
        pos[2] += r->rdir[2]*t;
        return(ax);
}


static
checkhit(r, cu)                 /* check for hit in full cube */
register RAY  *r;
CUBE  *cu;
{
        OBJECT  oset[MAXSET+1];
        register OBJREC  *o;
        register int  i;

        objset(oset, cu->cutree);
        for (i = oset[0]; i > 0; i--) {
                o = objptr(oset[i]);
                if (o->lastrno == r->rno)               /* checked already? */
                        continue;
                (*ofun[o->otype].funp)(o, r);
                o->lastrno = r->rno;
        }
        if (r->ro == NULL)
                return(0);                      /* no scores yet */

        return(incube(cu, r->rop));             /* hit OK if in current cube */
}
Revision:	1.5
Committed:	Wed Jul 19 18:46:59 1989 UTC (36 years, 3 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.4:	+7 -6 lines
Log Message:	changed location of clip test
#	User	Rev	Content
1	greg	1.1	/* Copyright (c) 1986 Regents of the University of California */
2
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* raytrace.c - routines for tracing and shading rays.
9			*
10			* 8/7/85
11			*/
12
13			#include "ray.h"
14
15			#include "octree.h"
16
17			#include "otypes.h"
18
19			extern CUBE thescene; /* our scene */
20			extern int maxdepth; /* maximum recursion depth */
21			extern double minweight; /* minimum ray weight */
22
23			long nrays = 0L; /* number of rays traced */
24
25	greg	1.4	#define MAXLOOP 1024 /* modifier loop detection */
26	greg	1.1
27			#define RAYHIT (-1) /* return value for intercepted ray */
28
29
30			rayorigin(r, ro, rt, rw) /* start new ray from old one */
31			register RAY r, ro;
32			int rt;
33			double rw;
34			{
35			if ((r->parent = ro) == NULL) { /* primary ray */
36			r->rlvl = 0;
37			r->rweight = rw;
38			r->crtype = r->rtype = rt;
39			r->rsrc = -1;
40			r->clipset = NULL;
41			} else { /* spawned ray */
42			r->rlvl = ro->rlvl;
43			if (rt & RAYREFL) {
44			r->rlvl++;
45			r->rsrc = -1;
46			r->clipset = ro->clipset;
47			} else {
48			r->rsrc = ro->rsrc;
49			r->clipset = ro->newcset;
50			}
51			r->rweight = ro->rweight * rw;
52			r->crtype = ro->crtype \| (r->rtype = rt);
53			VCOPY(r->rorg, ro->rop);
54			}
55			r->rno = nrays;
56			r->newcset = r->clipset;
57			r->ro = NULL;
58			r->rot = FHUGE;
59			r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
60			setcolor(r->pcol, 1.0, 1.0, 1.0);
61			setcolor(r->rcol, 0.0, 0.0, 0.0);
62			return(r->rlvl <= maxdepth && r->rweight >= minweight ? 0 : -1);
63			}
64
65
66			rayvalue(r) /* compute a ray's value */
67			register RAY *r;
68			{
69			extern int (*trace)();
70
71	greg	1.5	if (localhit(r, &thescene) \|\| sourcehit(r))
72	greg	1.1	rayshade(r, r->ro->omod);
73
74			if (trace != NULL)
75			(trace)(r); / trace execution */
76			}
77
78
79			raytrans(r) /* transmit ray as is */
80			RAY *r;
81			{
82			RAY tr;
83
84			if (rayorigin(&tr, r, TRANS, 1.0) == 0) {
85			VCOPY(tr.rdir, r->rdir);
86			rayvalue(&tr);
87			copycolor(r->rcol, tr.rcol);
88			}
89			}
90
91
92			rayshade(r, mod) /* shade ray r with material mod */
93			register RAY *r;
94			int mod;
95			{
96			static int depth = 0;
97			register OBJREC *m;
98	greg	1.5	/* check for clipped surface */
99			if (r->clipset != NULL && r->rot < FHUGE &&
100			inset(r->clipset, mod)) {
101			raytrans(r);
102			return;
103			}
104	greg	1.1	/* check for infinite loop */
105			if (depth++ >= MAXLOOP)
106	greg	1.4	objerror(r->ro, USER, "possible modifier loop");
107	greg	1.1	for ( ; mod != OVOID; mod = m->omod) {
108			m = objptr(mod);
109	greg	1.4	/****** unnecessary test since modifier() is always called
110	greg	1.1	if (!ismodifier(m->otype)) {
111			sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
112			error(USER, errmsg);
113			}
114	greg	1.4	******/
115	greg	1.1	(ofun[m->otype].funp)(m, r); / execute function */
116			m->lastrno = r->rno;
117			if (ismaterial(m->otype)) { /* materials call raytexture */
118			depth--;
119			return; /* we're done */
120			}
121			}
122			objerror(r->ro, USER, "material not found");
123			}
124
125
126			raytexture(r, mod) /* get material modifiers */
127			RAY *r;
128			int mod;
129			{
130			static int depth = 0;
131			register OBJREC *m;
132			/* check for infinite loop */
133			if (depth++ >= MAXLOOP)
134			objerror(r->ro, USER, "modifier loop");
135			/* execute textures and patterns */
136			for ( ; mod != OVOID; mod = m->omod) {
137			m = objptr(mod);
138			if (!istexture(m->otype)) {
139			sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
140			error(USER, errmsg);
141			}
142			(*ofun[m->otype].funp)(m, r);
143			m->lastrno = r->rno;
144			}
145			depth--; /* end here */
146			}
147
148
149			raymixture(r, fore, back, coef) /* mix modifiers */
150			register RAY *r;
151			OBJECT fore, back;
152			double coef;
153			{
154			FVECT curpert, forepert, backpert;
155			COLOR curpcol, forepcol, backpcol;
156			register int i;
157			/* clip coefficient */
158			if (coef > 1.0)
159			coef = 1.0;
160			else if (coef < 0.0)
161			coef = 0.0;
162			/* save current mods */
163			VCOPY(curpert, r->pert);
164			copycolor(curpcol, r->pcol);
165			/* compute new mods */
166			/* foreground */
167			r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
168			setcolor(r->pcol, 1.0, 1.0, 1.0);
169			if (fore != OVOID && coef > FTINY)
170			raytexture(r, fore);
171			VCOPY(forepert, r->pert);
172			copycolor(forepcol, r->pcol);
173			/* background */
174			r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
175			setcolor(r->pcol, 1.0, 1.0, 1.0);
176			if (back != OVOID && coef < 1.0-FTINY)
177			raytexture(r, back);
178			VCOPY(backpert, r->pert);
179			copycolor(backpcol, r->pcol);
180			/* sum perturbations */
181			for (i = 0; i < 3; i++)
182			r->pert[i] = curpert[i] + coef*forepert[i] +
183			(1.0-coef)*backpert[i];
184			/* multiply colors */
185			setcolor(r->pcol, coef*colval(forepcol,RED) +
186			(1.0-coef)*colval(backpcol,RED),
187			coef*colval(forepcol,GRN) +
188			(1.0-coef)*colval(backpcol,GRN),
189			coef*colval(forepcol,BLU) +
190			(1.0-coef)*colval(backpcol,BLU));
191			multcolor(r->pcol, curpcol);
192			}
193
194
195			double
196			raynormal(norm, r) /* compute perturbed normal for ray */
197			FVECT norm;
198			register RAY *r;
199			{
200			double newdot;
201			register int i;
202
203			/* The perturbation is added to the surface normal to obtain
204			* the new normal. If the new normal would affect the surface
205			* orientation wrt. the ray, a correction is made. The method is
206			* still fraught with problems since reflected rays and similar
207			* directions calculated from the surface normal may spawn rays behind
208			* the surface. The only solution is to curb textures at high
209			* incidence (Rdot << 1).
210			*/
211
212			for (i = 0; i < 3; i++)
213			norm[i] = r->ron[i] + r->pert[i];
214
215			if (normalize(norm) == 0.0) {
216			objerror(r->ro, WARNING, "illegal normal perturbation");
217			VCOPY(norm, r->ron);
218			return(r->rod);
219			}
220			newdot = -DOT(norm, r->rdir);
221			if ((newdot > 0.0) != (r->rod > 0.0)) { /* fix orientation */
222			for (i = 0; i < 3; i++)
223			norm[i] += 2.0newdotr->rdir[i];
224			newdot = -newdot;
225			}
226			return(newdot);
227			}
228
229
230			flipsurface(r) /* reverse surface orientation */
231			register RAY *r;
232			{
233			r->rod = -r->rod;
234			r->ron[0] = -r->ron[0];
235			r->ron[1] = -r->ron[1];
236			r->ron[2] = -r->ron[2];
237			r->pert[0] = -r->pert[0];
238			r->pert[1] = -r->pert[1];
239			r->pert[2] = -r->pert[2];
240			}
241
242
243			localhit(r, scene) /* check for hit in the octree */
244			register RAY *r;
245			register CUBE *scene;
246			{
247			FVECT curpos; /* current cube position */
248			int mpos, mneg; /* sign flags */
249			double t, dt;
250			register int i;
251
252			nrays++; /* increment trace counter */
253
254			mpos = mneg = 0;
255			for (i = 0; i < 3; i++) {
256			curpos[i] = r->rorg[i];
257			if (r->rdir[i] > FTINY)
258			mpos \|= 1 << i;
259			else if (r->rdir[i] < -FTINY)
260			mneg \|= 1 << i;
261			}
262			t = 0.0;
263			if (!incube(scene, curpos)) {
264			/* find distance to entry */
265			for (i = 0; i < 3; i++) {
266			/* plane in our direction */
267			if (mpos & 1<<i)
268			dt = scene->cuorg[i];
269			else if (mneg & 1<<i)
270			dt = scene->cuorg[i] + scene->cusize;
271			else
272			continue;
273			/* distance to the plane */
274			dt = (dt - r->rorg[i])/r->rdir[i];
275			if (dt > t)
276			t = dt; /* farthest face is the one */
277			}
278			t += FTINY; /* fudge to get inside cube */
279			/* advance position */
280			for (i = 0; i < 3; i++)
281			curpos[i] += r->rdir[i]*t;
282
283			if (!incube(scene, curpos)) /* non-intersecting ray */
284			return(0);
285			}
286			return(raymove(curpos, mpos, mneg, r, scene) == RAYHIT);
287			}
288
289
290			static int
291			raymove(pos, plus, minus, r, cu) /* check for hit as we move */
292			FVECT pos; /* modified */
293			int plus, minus; /* direction indicators to speed tests */
294			register RAY *r;
295			register CUBE *cu;
296			{
297			int ax;
298			double dt, t;
299			register int sgn;
300
301			if (istree(cu->cutree)) { /* recurse on subcubes */
302			CUBE cukid;
303			register int br;
304
305			cukid.cusize = cu->cusize * 0.5; /* find subcube */
306			VCOPY(cukid.cuorg, cu->cuorg);
307			br = 0;
308			if (pos[0] >= cukid.cuorg[0]+cukid.cusize) {
309			cukid.cuorg[0] += cukid.cusize;
310			br \|= 1;
311			}
312			if (pos[1] >= cukid.cuorg[1]+cukid.cusize) {
313			cukid.cuorg[1] += cukid.cusize;
314			br \|= 2;
315			}
316			if (pos[2] >= cukid.cuorg[2]+cukid.cusize) {
317			cukid.cuorg[2] += cukid.cusize;
318			br \|= 4;
319			}
320			for ( ; ; ) {
321			cukid.cutree = octkid(cu->cutree, br);
322			if ((ax = raymove(pos,plus,minus,r,&cukid)) == RAYHIT)
323			return(RAYHIT);
324			sgn = 1 << ax;
325			if (sgn & minus) /* negative axis? */
326			if (sgn & br) {
327			cukid.cuorg[ax] -= cukid.cusize;
328			br &= ~sgn;
329			} else
330			return(ax); /* underflow */
331			else
332			if (sgn & br)
333			return(ax); /* overflow */
334			else {
335			cukid.cuorg[ax] += cukid.cusize;
336			br \|= sgn;
337			}
338			}
339			/NOTREACHED/
340			}
341			if (isfull(cu->cutree) && checkhit(r, cu))
342			return(RAYHIT);
343			/* advance to next cube */
344			sgn = plus \| minus;
345			if (sgn&1) {
346			dt = plus&1 ? cu->cuorg[0] + cu->cusize : cu->cuorg[0];
347			t = (dt - pos[0])/r->rdir[0];
348			ax = 0;
349			} else
350			t = FHUGE;
351			if (sgn&2) {
352			dt = plus&2 ? cu->cuorg[1] + cu->cusize : cu->cuorg[1];
353			dt = (dt - pos[1])/r->rdir[1];
354			if (dt < t) {
355			t = dt;
356			ax = 1;
357			}
358			}
359			if (sgn&4) {
360			dt = plus&4 ? cu->cuorg[2] + cu->cusize : cu->cuorg[2];
361			dt = (dt - pos[2])/r->rdir[2];
362			if (dt < t) {
363			t = dt;
364			ax = 2;
365			}
366			}
367			pos[0] += r->rdir[0]*t;
368			pos[1] += r->rdir[1]*t;
369			pos[2] += r->rdir[2]*t;
370			return(ax);
371			}
372
373
374			static
375			checkhit(r, cu) /* check for hit in full cube */
376			register RAY *r;
377			CUBE *cu;
378			{
379			OBJECT oset[MAXSET+1];
380			register OBJREC *o;
381			register int i;
382
383			objset(oset, cu->cutree);
384			for (i = oset[0]; i > 0; i--) {
385			o = objptr(oset[i]);
386			if (o->lastrno == r->rno) /* checked already? */
387			continue;
388			(*ofun[o->otype].funp)(o, r);
389			o->lastrno = r->rno;
390			}
391			if (r->ro == NULL)
392			return(0); /* no scores yet */
393
394			return(incube(cu, r->rop)); /* hit OK if in current cube */
395			}