src/hd/rhdisp3.c

/* Copyright (c) 1998 Silicon Graphics, Inc. */

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

/*
 * Holodeck beam support for display process
 */

#include "rholo.h"
#include "rhdisp.h"
#include "view.h"

struct cellist {
        GCOORD  *cl;
        int     n;
};


int
npixels(vp, hr, vr, hp, bi)     /* compute appropriate nrays to evaluate */
register VIEW   *vp;
int     hr, vr;
HOLO    *hp;
int     bi;
{
        VIEW    vrev;
        GCOORD  gc[2];
        FVECT   cp[4], ip[4], pf, pb;
        double  af, ab, sf2, sb2, dfb2, df2, db2, penalty;
        register int    i;
                                        /* special case */
        if (hr <= 0 | vr <= 0)
                return(0);
                                        /* compute cell corners in image */
        if (!hdbcoord(gc, hp, bi))
                error(CONSISTENCY, "bad beam index in npixels");
        hdcell(cp, hp, gc+1);           /* find cell on front image */
        for (i = 3; i--; )              /* compute front center */
                pf[i] = 0.5*(cp[0][i] + cp[2][i]);
        sf2 = 0.25*dist2(cp[0], cp[2]); /* compute half diagonal length */
        for (i = 0; i < 4; i++) {       /* compute visible quad */
                viewloc(ip[i], vp, cp[i]);
                if (ip[i][2] < 0.) {
                        af = 0;
                        goto getback;
                }
                ip[i][0] *= (double)hr; /* scale by resolution */
                ip[i][1] *= (double)vr;
        }
                                        /* compute front area */
        af = (ip[1][0]-ip[0][0])*(ip[2][1]-ip[0][1]) -
                (ip[2][0]-ip[0][0])*(ip[1][1]-ip[0][1]);
        af += (ip[2][0]-ip[3][0])*(ip[1][1]-ip[3][1]) -
                (ip[1][0]-ip[3][0])*(ip[2][1]-ip[3][1]);
        af *= af >= 0 ? 0.5 : -0.5;
getback:
        copystruct(&vrev, vp);          /* compute reverse view */
        for (i = 0; i < 3; i++) {
                vrev.vdir[i] = -vp->vdir[i];
                vrev.vup[i] = -vp->vup[i];
                vrev.hvec[i] = -vp->hvec[i];
                vrev.vvec[i] = -vp->vvec[i];
        }
        hdcell(cp, hp, gc);             /* find cell on back image */
        for (i = 3; i--; )              /* compute rear center */
                pb[i] = 0.5*(cp[0][i] + cp[2][i]);
        sb2 = 0.25*dist2(cp[0], cp[2]); /* compute half diagonal length */
        for (i = 0; i < 4; i++) {       /* compute visible quad */
                viewloc(ip[i], &vrev, cp[i]);
                if (ip[i][2] < 0.) {
                        ab = 0;
                        goto finish;
                }
                ip[i][0] *= (double)hr; /* scale by resolution */
                ip[i][1] *= (double)vr;
        }
                                        /* compute back area */
        ab = (ip[1][0]-ip[0][0])*(ip[2][1]-ip[0][1]) -
                (ip[2][0]-ip[0][0])*(ip[1][1]-ip[0][1]);
        ab += (ip[2][0]-ip[3][0])*(ip[1][1]-ip[3][1]) -
                (ip[1][0]-ip[3][0])*(ip[2][1]-ip[3][1]);
        ab *= ab >= 0 ? 0.5 : -0.5;
finish:         /* compute penalty based on dist. sightline - viewpoint */
        df2 = dist2(vp->vp, pf);
        db2 = dist2(vp->vp, pb);
        dfb2 = dist2(pf, pb);
        penalty = dfb2 + df2 - db2;
        penalty = df2 - 0.25*penalty*penalty/dfb2;
        if (df2 > db2)  penalty /= df2 <= dfb2 ? sb2 : sb2*df2/dfb2;
        else            penalty /= db2 <= dfb2 ? sf2 : sf2*db2/dfb2;
        if (penalty < 1.) penalty = 1.;
                                        /* round off smaller non-zero area */
        if (ab <= FTINY || (af > FTINY && af <= ab))
                return((int)(af/penalty + 0.5));
        return((int)(ab/penalty + 0.5));
}


/*
 * The ray directions that define the pyramid in visit_cells() needn't
 * be normalized, but they must be given in clockwise order as seen
 * from the pyramid's apex (origin).
 * If no cell centers fall within the domain, the closest cell is visited.
 */
int
visit_cells(orig, pyrd, hp, vf, dp)     /* visit cells within a pyramid */
FVECT   orig, pyrd[4];          /* pyramid ray directions in clockwise order */
register HOLO   *hp;
int     (*vf)();
char    *dp;
{
        int     ncalls = 0, n = 0;
        int     inflags = 0;
        FVECT   gp, pn[4], lo, ld;
        double  po[4], lbeg, lend, d, t;
        GCOORD  gc, gc2[2];
        register int    i;
                                        /* figure out whose side we're on */
        hdgrid(gp, hp, orig);
        for (i = 0; i < 3; i++) {
                inflags |= (gp[i] > FTINY) << (i<<1);
                inflags |= (gp[i] < hp->grid[i]-FTINY) << (i<<1 | 1);
        }
                                        /* compute pyramid planes */
        for (i = 0; i < 4; i++) {
                fcross(pn[i], pyrd[i], pyrd[(i+1)&03]);
                po[i] = DOT(pn[i], orig);
        }
                                        /* traverse each wall */
        for (gc.w = 0; gc.w < 6; gc.w++) {
                if (!(inflags & 1<<gc.w))       /* origin on wrong side */
                        continue;
                                        /* scanline algorithm */
                for (gc.i[1] = hp->grid[hdwg1[gc.w]]; gc.i[1]--; ) {
                                                /* compute scanline */
                        gp[gc.w>>1] = gc.w&1 ? hp->grid[gc.w>>1] : 0;
                        gp[hdwg0[gc.w]] = 0;
                        gp[hdwg1[gc.w]] = gc.i[1] + 0.5;
                        hdworld(lo, hp, gp);
                        gp[hdwg0[gc.w]] = 1;
                        hdworld(ld, hp, gp);
                        ld[0] -= lo[0]; ld[1] -= lo[1]; ld[2] -= lo[2];
                                                /* find scanline limits */
                        lbeg = 0; lend = hp->grid[hdwg0[gc.w]];
                        for (i = 0; i < 4; i++) {
                                t = DOT(pn[i], lo) - po[i];
                                d = -DOT(pn[i], ld);
                                if (d > FTINY) {                /* <- plane */
                                        if ((t /= d) < lend)
                                                lend = t;
                                } else if (d < -FTINY) {        /* plane -> */
                                        if ((t /= d) > lbeg)
                                                lbeg = t;
                                } else if (t < 0) {             /* outside */
                                        lend = -1;
                                        break;
                                }
                        }
                        if (lbeg >= lend)
                                continue;
                        i = lend + .5;          /* visit cells on this scan */
                        for (gc.i[0] = lbeg + .5; gc.i[0] < i; gc.i[0]++) {
                                n += (*vf)(&gc, dp);
                                ncalls++;
                        }
                }
        }
        if (ncalls)                     /* got one at least */
                return(n);
                                        /* else find closest cell */
        VSUM(ld, pyrd[0], pyrd[1], 1.);
        VSUM(ld, ld, pyrd[2], 1.);
        VSUM(ld, ld, pyrd[3], 1.);
#if 0
        if (normalize(ld) == 0.0)       /* technically not necessary */
                return(0);
#endif
        d = hdinter(gc2, NULL, &t, hp, orig, ld);
        if (d >= FHUGE || t <= 0.)
                return(0);
        return((*vf)(gc2+1, dp));       /* visit it */
}


sect_behind(hp, vp)             /* check if section is "behind" viewpoint */
register HOLO   *hp;
register VIEW   *vp;
{
        FVECT   hcent;
                                        /* compute holodeck section center */
        VSUM(hcent, hp->orig, hp->xv[0], 0.5);
        VSUM(hcent, hcent, hp->xv[1], 0.5);
        VSUM(hcent, hcent, hp->xv[2], 0.5);
                                        /* behind if center is behind */
        return(DOT(vp->vdir,hcent) < DOT(vp->vdir,vp->vp));
}


viewpyramid(org, dir, hp, vp)   /* compute view pyramid */
FVECT   org, dir[4];
HOLO    *hp;
VIEW    *vp;
{
        register int    i;
                                        /* check view type */
        if (vp->type == VT_PAR)
                return(0);
                                        /* in front or behind? */
        if (!sect_behind(hp, vp)) {
                if (viewray(org, dir[0], vp, 0., 0.) < -FTINY)
                        return(0);
                if (viewray(org, dir[1], vp, 0., 1.) < -FTINY)
                        return(0);
                if (viewray(org, dir[2], vp, 1., 1.) < -FTINY)
                        return(0);
                if (viewray(org, dir[3], vp, 1., 0.) < -FTINY)
                        return(0);
                return(1);
        }                               /* reverse pyramid */
        if (viewray(org, dir[3], vp, 0., 0.) < -FTINY)
                return(0);
        if (viewray(org, dir[2], vp, 0., 1.) < -FTINY)
                return(0);
        if (viewray(org, dir[1], vp, 1., 1.) < -FTINY)
                return(0);
        if (viewray(org, dir[0], vp, 1., 0.) < -FTINY)
                return(0);
        for (i = 0; i < 3; i++) {
                dir[0][i] = -dir[0][i];
                dir[1][i] = -dir[1][i];
                dir[2][i] = -dir[2][i];
                dir[3][i] = -dir[3][i];
        }
        return(-1);
}


int
addcell(gcp, cl)                /* add a cell to a list */
GCOORD  *gcp;
register struct cellist *cl;
{
        copystruct(cl->cl+cl->n, gcp);
        cl->n++;
        return(1);
}


int
cellcmp(gcp1, gcp2)             /* visit_cells() cell ordering */
register GCOORD *gcp1, *gcp2;
{
        register int    c;

        if ((c = gcp1->w - gcp2->w))
                return(c);
        if ((c = gcp2->i[1] - gcp1->i[1]))      /* wg1 is reverse-ordered */
                return(c);
        return(gcp1->i[0] - gcp2->i[0]);
}


GCOORD *
getviewcells(np, hp, vp)        /* get ordered cell list for section view */
int     *np;            /* returned number of cells (negative if reversed) */
register HOLO   *hp;
VIEW    *vp;
{
        FVECT   org, dir[4];
        int     orient;
        struct cellist  cl;
                                        /* compute view pyramid */
        *np = 0;
        orient = viewpyramid(org, dir, hp, vp);
        if (!orient)
                return(NULL);
                                        /* allocate enough list space */
        cl.n = 2*(      hp->grid[0]*hp->grid[1] +
                        hp->grid[0]*hp->grid[2] +
                        hp->grid[1]*hp->grid[2] );
        cl.cl = (GCOORD *)malloc(cl.n*sizeof(GCOORD));
        if (cl.cl == NULL)
                goto memerr;
        cl.n = 0;                       /* add cells within pyramid */
        visit_cells(org, dir, hp, addcell, (char *)&cl);
        if (!cl.n) {
                free((char *)cl.cl);
                return(NULL);
        }
        *np = cl.n * orient;
#if 0
        /* We're just going to free this memory in a moment, and list is
         * sorted automatically by visit_cells(), so we don't need this.
         */
                                        /* optimize memory use */
        cl.cl = (GCOORD *)realloc((char *)cl.cl, cl.n*sizeof(GCOORD));
        if (cl.cl == NULL)
                goto memerr;
                                        /* sort the list */
        qsort((char *)cl.cl, cl.n, sizeof(GCOORD), cellcmp);
#endif
        return(cl.cl);
memerr:
        error(SYSTEM, "out of memory in getviewcells");
}


gridlines(f)                    /* run through holodeck section grid lines */
int     (*f)();
{
        register int    hd, w, i;
        int     g0, g1;
        FVECT   wp[2], mov;
        double  d;
                                        /* do each wall on each section */
        for (hd = 0; hdlist[hd] != NULL; hd++)
                for (w = 0; w < 6; w++) {
                        g0 = hdwg0[w];
                        g1 = hdwg1[w];
                        d = 1.0/hdlist[hd]->grid[g0];
                        mov[0] = d * hdlist[hd]->xv[g0][0];
                        mov[1] = d * hdlist[hd]->xv[g0][1];
                        mov[2] = d * hdlist[hd]->xv[g0][2];
                        if (w & 1) {
                                VSUM(wp[0], hdlist[hd]->orig,
                                                hdlist[hd]->xv[w>>1], 1.);
                                VSUM(wp[0], wp[0], mov, 1.);
                        } else
                                VCOPY(wp[0], hdlist[hd]->orig);
                        VSUM(wp[1], wp[0], hdlist[hd]->xv[g1], 1.);
                        for (i = hdlist[hd]->grid[g0]; ; ) {    /* g0 lines */
                                (*f)(wp);
                                if (!--i) break;
                                wp[0][0] += mov[0]; wp[0][1] += mov[1];
                                wp[0][2] += mov[2]; wp[1][0] += mov[0];
                                wp[1][1] += mov[1]; wp[1][2] += mov[2];
                        }
                        d = 1.0/hdlist[hd]->grid[g1];
                        mov[0] = d * hdlist[hd]->xv[g1][0];
                        mov[1] = d * hdlist[hd]->xv[g1][1];
                        mov[2] = d * hdlist[hd]->xv[g1][2];
                        if (w & 1)
                                VSUM(wp[0], hdlist[hd]->orig,
                                                hdlist[hd]->xv[w>>1], 1.);
                        else
                                VSUM(wp[0], hdlist[hd]->orig, mov, 1.);
                        VSUM(wp[1], wp[0], hdlist[hd]->xv[g0], 1.);
                        for (i = hdlist[hd]->grid[g1]; ; ) {    /* g1 lines */
                                (*f)(wp);
                                if (!--i) break;
                                wp[0][0] += mov[0]; wp[0][1] += mov[1];
                                wp[0][2] += mov[2]; wp[1][0] += mov[0];
                                wp[1][1] += mov[1]; wp[1][2] += mov[2];
                        }
                }
}
Revision:	3.11
Committed:	Thu Nov 5 13:58:37 1998 UTC (25 years, 5 months ago) by gwlarson
Content type:	text/plain
Branch:	MAIN
Changes since 3.10:	+4 -1 lines
Log Message:	changed beam management to allow temporary override
#	User	Rev	Content
1	gwlarson	3.10	/* Copyright (c) 1998 Silicon Graphics, Inc. */
2	gregl	3.1
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ SGI";
5			#endif
6
7			/*
8	gregl	3.2	* Holodeck beam support for display process
9	gregl	3.1	*/
10
11			#include "rholo.h"
12			#include "rhdisp.h"
13			#include "view.h"
14
15	gregl	3.4	struct cellist {
16			GCOORD *cl;
17			int n;
18			};
19	gregl	3.1
20	gregl	3.4
21	gregl	3.1	int
22	gwlarson	3.10	npixels(vp, hr, vr, hp, bi) /* compute appropriate nrays to evaluate */
23	gregl	3.5	register VIEW *vp;
24	gregl	3.1	int hr, vr;
25			HOLO *hp;
26			int bi;
27			{
28	gregl	3.5	VIEW vrev;
29	gregl	3.1	GCOORD gc[2];
30	gwlarson	3.10	FVECT cp[4], ip[4], pf, pb;
31			double af, ab, sf2, sb2, dfb2, df2, db2, penalty;
32	gregl	3.1	register int i;
33	gwlarson	3.11	/* special case */
34			if (hr <= 0 \| vr <= 0)
35			return(0);
36	gregl	3.1	/* compute cell corners in image */
37			if (!hdbcoord(gc, hp, bi))
38			error(CONSISTENCY, "bad beam index in npixels");
39	gregl	3.5	hdcell(cp, hp, gc+1); /* find cell on front image */
40	gwlarson	3.10	for (i = 3; i--; ) /* compute front center */
41			pf[i] = 0.5*(cp[0][i] + cp[2][i]);
42			sf2 = 0.25dist2(cp[0], cp[2]); / compute half diagonal length */
43			for (i = 0; i < 4; i++) { /* compute visible quad */
44	gregl	3.5	viewloc(ip[i], vp, cp[i]);
45			if (ip[i][2] < 0.) {
46			af = 0;
47			goto getback;
48	gregl	3.4	}
49	gregl	3.5	ip[i][0] = (double)hr; / scale by resolution */
50			ip[i][1] *= (double)vr;
51	gregl	3.4	}
52	gregl	3.5	/* compute front area */
53			af = (ip[1][0]-ip[0][0])*(ip[2][1]-ip[0][1]) -
54			(ip[2][0]-ip[0][0])*(ip[1][1]-ip[0][1]);
55			af += (ip[2][0]-ip[3][0])*(ip[1][1]-ip[3][1]) -
56			(ip[1][0]-ip[3][0])*(ip[2][1]-ip[3][1]);
57	gwlarson	3.10	af *= af >= 0 ? 0.5 : -0.5;
58	gregl	3.5	getback:
59			copystruct(&vrev, vp); /* compute reverse view */
60			for (i = 0; i < 3; i++) {
61			vrev.vdir[i] = -vp->vdir[i];
62			vrev.vup[i] = -vp->vup[i];
63			vrev.hvec[i] = -vp->hvec[i];
64			vrev.vvec[i] = -vp->vvec[i];
65			}
66			hdcell(cp, hp, gc); /* find cell on back image */
67	gwlarson	3.10	for (i = 3; i--; ) /* compute rear center */
68			pb[i] = 0.5*(cp[0][i] + cp[2][i]);
69			sb2 = 0.25dist2(cp[0], cp[2]); / compute half diagonal length */
70			for (i = 0; i < 4; i++) { /* compute visible quad */
71	gregl	3.5	viewloc(ip[i], &vrev, cp[i]);
72	gwlarson	3.10	if (ip[i][2] < 0.) {
73			ab = 0;
74			goto finish;
75			}
76	gregl	3.1	ip[i][0] = (double)hr; / scale by resolution */
77			ip[i][1] *= (double)vr;
78			}
79	gregl	3.5	/* compute back area */
80			ab = (ip[1][0]-ip[0][0])*(ip[2][1]-ip[0][1]) -
81	gregl	3.1	(ip[2][0]-ip[0][0])*(ip[1][1]-ip[0][1]);
82	gregl	3.5	ab += (ip[2][0]-ip[3][0])*(ip[1][1]-ip[3][1]) -
83	gregl	3.1	(ip[1][0]-ip[3][0])*(ip[2][1]-ip[3][1]);
84	gwlarson	3.10	ab *= ab >= 0 ? 0.5 : -0.5;
85			finish: /* compute penalty based on dist. sightline - viewpoint */
86			df2 = dist2(vp->vp, pf);
87			db2 = dist2(vp->vp, pb);
88			dfb2 = dist2(pf, pb);
89			penalty = dfb2 + df2 - db2;
90			penalty = df2 - 0.25penaltypenalty/dfb2;
91			if (df2 > db2) penalty /= df2 <= dfb2 ? sb2 : sb2*df2/dfb2;
92			else penalty /= db2 <= dfb2 ? sf2 : sf2*db2/dfb2;
93			if (penalty < 1.) penalty = 1.;
94			/* round off smaller non-zero area */
95			if (ab <= FTINY \|\| (af > FTINY && af <= ab))
96			return((int)(af/penalty + 0.5));
97			return((int)(ab/penalty + 0.5));
98	gregl	3.1	}
99
100
101			/*
102			* The ray directions that define the pyramid in visit_cells() needn't
103			* be normalized, but they must be given in clockwise order as seen
104			* from the pyramid's apex (origin).
105	gregl	3.8	* If no cell centers fall within the domain, the closest cell is visited.
106	gregl	3.1	*/
107			int
108			visit_cells(orig, pyrd, hp, vf, dp) /* visit cells within a pyramid */
109			FVECT orig, pyrd[4]; /* pyramid ray directions in clockwise order */
110	gregl	3.8	register HOLO *hp;
111	gregl	3.1	int (*vf)();
112			char *dp;
113			{
114	gregl	3.8	int ncalls = 0, n = 0;
115	gregl	3.1	int inflags = 0;
116			FVECT gp, pn[4], lo, ld;
117			double po[4], lbeg, lend, d, t;
118	gregl	3.8	GCOORD gc, gc2[2];
119	gregl	3.1	register int i;
120			/* figure out whose side we're on */
121			hdgrid(gp, hp, orig);
122			for (i = 0; i < 3; i++) {
123			inflags \|= (gp[i] > FTINY) << (i<<1);
124			inflags \|= (gp[i] < hp->grid[i]-FTINY) << (i<<1 \| 1);
125			}
126			/* compute pyramid planes */
127			for (i = 0; i < 4; i++) {
128			fcross(pn[i], pyrd[i], pyrd[(i+1)&03]);
129			po[i] = DOT(pn[i], orig);
130			}
131			/* traverse each wall */
132			for (gc.w = 0; gc.w < 6; gc.w++) {
133			if (!(inflags & 1<<gc.w)) /* origin on wrong side */
134			continue;
135			/* scanline algorithm */
136	gregl	3.9	for (gc.i[1] = hp->grid[hdwg1[gc.w]]; gc.i[1]--; ) {
137	gregl	3.1	/* compute scanline */
138			gp[gc.w>>1] = gc.w&1 ? hp->grid[gc.w>>1] : 0;
139	gregl	3.9	gp[hdwg0[gc.w]] = 0;
140			gp[hdwg1[gc.w]] = gc.i[1] + 0.5;
141	gregl	3.1	hdworld(lo, hp, gp);
142	gregl	3.9	gp[hdwg0[gc.w]] = 1;
143	gregl	3.1	hdworld(ld, hp, gp);
144	gregl	3.2	ld[0] -= lo[0]; ld[1] -= lo[1]; ld[2] -= lo[2];
145	gregl	3.1	/* find scanline limits */
146	gregl	3.9	lbeg = 0; lend = hp->grid[hdwg0[gc.w]];
147	gregl	3.1	for (i = 0; i < 4; i++) {
148			t = DOT(pn[i], lo) - po[i];
149			d = -DOT(pn[i], ld);
150	gregl	3.2	if (d > FTINY) { /* <- plane */
151	gregl	3.1	if ((t /= d) < lend)
152			lend = t;
153	gregl	3.2	} else if (d < -FTINY) { /* plane -> */
154	gregl	3.1	if ((t /= d) > lbeg)
155			lbeg = t;
156	gregl	3.3	} else if (t < 0) { /* outside */
157			lend = -1;
158			break;
159			}
160	gregl	3.1	}
161	gregl	3.3	if (lbeg >= lend)
162			continue;
163	gregl	3.1	i = lend + .5; /* visit cells on this scan */
164	gregl	3.8	for (gc.i[0] = lbeg + .5; gc.i[0] < i; gc.i[0]++) {
165	gregl	3.1	n += (*vf)(&gc, dp);
166	gregl	3.8	ncalls++;
167			}
168	gregl	3.1	}
169			}
170	gregl	3.8	if (ncalls) /* got one at least */
171			return(n);
172			/* else find closest cell */
173			VSUM(ld, pyrd[0], pyrd[1], 1.);
174			VSUM(ld, ld, pyrd[2], 1.);
175			VSUM(ld, ld, pyrd[3], 1.);
176			#if 0
177			if (normalize(ld) == 0.0) /* technically not necessary */
178			return(0);
179			#endif
180			d = hdinter(gc2, NULL, &t, hp, orig, ld);
181			if (d >= FHUGE \|\| t <= 0.)
182			return(0);
183			return((vf)(gc2+1, dp)); / visit it */
184	gregl	3.1	}
185
186
187	gregl	3.4	sect_behind(hp, vp) /* check if section is "behind" viewpoint */
188			register HOLO *hp;
189			register VIEW *vp;
190			{
191			FVECT hcent;
192			/* compute holodeck section center */
193			VSUM(hcent, hp->orig, hp->xv[0], 0.5);
194			VSUM(hcent, hcent, hp->xv[1], 0.5);
195			VSUM(hcent, hcent, hp->xv[2], 0.5);
196			/* behind if center is behind */
197			return(DOT(vp->vdir,hcent) < DOT(vp->vdir,vp->vp));
198			}
199
200
201			viewpyramid(org, dir, hp, vp) /* compute view pyramid */
202			FVECT org, dir[4];
203			HOLO *hp;
204			VIEW *vp;
205			{
206			register int i;
207			/* check view type */
208			if (vp->type == VT_PAR)
209			return(0);
210			/* in front or behind? */
211			if (!sect_behind(hp, vp)) {
212			if (viewray(org, dir[0], vp, 0., 0.) < -FTINY)
213			return(0);
214			if (viewray(org, dir[1], vp, 0., 1.) < -FTINY)
215			return(0);
216			if (viewray(org, dir[2], vp, 1., 1.) < -FTINY)
217			return(0);
218			if (viewray(org, dir[3], vp, 1., 0.) < -FTINY)
219			return(0);
220			return(1);
221			} /* reverse pyramid */
222			if (viewray(org, dir[3], vp, 0., 0.) < -FTINY)
223			return(0);
224			if (viewray(org, dir[2], vp, 0., 1.) < -FTINY)
225			return(0);
226			if (viewray(org, dir[1], vp, 1., 1.) < -FTINY)
227			return(0);
228			if (viewray(org, dir[0], vp, 1., 0.) < -FTINY)
229			return(0);
230			for (i = 0; i < 3; i++) {
231			dir[0][i] = -dir[0][i];
232			dir[1][i] = -dir[1][i];
233			dir[2][i] = -dir[2][i];
234			dir[3][i] = -dir[3][i];
235			}
236			return(-1);
237			}
238
239
240	gregl	3.1	int
241			addcell(gcp, cl) /* add a cell to a list */
242			GCOORD *gcp;
243	gregl	3.4	register struct cellist *cl;
244	gregl	3.1	{
245	gregl	3.4	copystruct(cl->cl+cl->n, gcp);
246			cl->n++;
247	gregl	3.1	return(1);
248			}
249
250
251			int
252			cellcmp(gcp1, gcp2) /* visit_cells() cell ordering */
253			register GCOORD gcp1, gcp2;
254			{
255			register int c;
256
257			if ((c = gcp1->w - gcp2->w))
258			return(c);
259			if ((c = gcp2->i[1] - gcp1->i[1])) /* wg1 is reverse-ordered */
260			return(c);
261			return(gcp1->i[0] - gcp2->i[0]);
262			}
263
264
265	gregl	3.4	GCOORD *
266			getviewcells(np, hp, vp) /* get ordered cell list for section view */
267			int np; / returned number of cells (negative if reversed) */
268	gregl	3.1	register HOLO *hp;
269			VIEW *vp;
270			{
271			FVECT org, dir[4];
272	gregl	3.4	int orient;
273			struct cellist cl;
274	gregl	3.1	/* compute view pyramid */
275	gregl	3.4	*np = 0;
276			orient = viewpyramid(org, dir, hp, vp);
277			if (!orient)
278			return(NULL);
279	gregl	3.1	/* allocate enough list space */
280	gregl	3.4	cl.n = 2( hp->grid[0]hp->grid[1] +
281			hp->grid[0]*hp->grid[2] +
282			hp->grid[1]*hp->grid[2] );
283			cl.cl = (GCOORD )malloc(cl.nsizeof(GCOORD));
284			if (cl.cl == NULL)
285	gregl	3.1	goto memerr;
286	gregl	3.4	cl.n = 0; /* add cells within pyramid */
287	gwlarson	3.11	visit_cells(org, dir, hp, addcell, (char *)&cl);
288	gregl	3.4	if (!cl.n) {
289			free((char *)cl.cl);
290	gregl	3.1	return(NULL);
291			}
292	gregl	3.4	np = cl.n orient;
293	gregl	3.1	#if 0
294	gregl	3.2	/* We're just going to free this memory in a moment, and list is
295			* sorted automatically by visit_cells(), so we don't need this.
296			*/
297	gregl	3.4	/* optimize memory use */
298			cl.cl = (GCOORD )realloc((char )cl.cl, cl.n*sizeof(GCOORD));
299			if (cl.cl == NULL)
300			goto memerr;
301	gregl	3.1	/* sort the list */
302	gregl	3.4	qsort((char *)cl.cl, cl.n, sizeof(GCOORD), cellcmp);
303	gregl	3.1	#endif
304	gregl	3.4	return(cl.cl);
305	gregl	3.1	memerr:
306			error(SYSTEM, "out of memory in getviewcells");
307			}
308	gregl	3.6
309
310			gridlines(f) /* run through holodeck section grid lines */
311			int (*f)();
312			{
313			register int hd, w, i;
314			int g0, g1;
315	gregl	3.7	FVECT wp[2], mov;
316	gregl	3.6	double d;
317			/* do each wall on each section */
318			for (hd = 0; hdlist[hd] != NULL; hd++)
319			for (w = 0; w < 6; w++) {
320	gregl	3.9	g0 = hdwg0[w];
321			g1 = hdwg1[w];
322	gregl	3.7	d = 1.0/hdlist[hd]->grid[g0];
323			mov[0] = d * hdlist[hd]->xv[g0][0];
324			mov[1] = d * hdlist[hd]->xv[g0][1];
325			mov[2] = d * hdlist[hd]->xv[g0][2];
326			if (w & 1) {
327	gregl	3.6	VSUM(wp[0], hdlist[hd]->orig,
328			hdlist[hd]->xv[w>>1], 1.);
329	gregl	3.7	VSUM(wp[0], wp[0], mov, 1.);
330			} else
331			VCOPY(wp[0], hdlist[hd]->orig);
332			VSUM(wp[1], wp[0], hdlist[hd]->xv[g1], 1.);
333			for (i = hdlist[hd]->grid[g0]; ; ) { /* g0 lines */
334	gregl	3.6	(*f)(wp);
335	gregl	3.7	if (!--i) break;
336			wp[0][0] += mov[0]; wp[0][1] += mov[1];
337			wp[0][2] += mov[2]; wp[1][0] += mov[0];
338			wp[1][1] += mov[1]; wp[1][2] += mov[2];
339	gregl	3.6	}
340	gregl	3.7	d = 1.0/hdlist[hd]->grid[g1];
341			mov[0] = d * hdlist[hd]->xv[g1][0];
342			mov[1] = d * hdlist[hd]->xv[g1][1];
343			mov[2] = d * hdlist[hd]->xv[g1][2];
344			if (w & 1)
345	gregl	3.6	VSUM(wp[0], hdlist[hd]->orig,
346			hdlist[hd]->xv[w>>1], 1.);
347	gregl	3.7	else
348			VSUM(wp[0], hdlist[hd]->orig, mov, 1.);
349			VSUM(wp[1], wp[0], hdlist[hd]->xv[g0], 1.);
350			for (i = hdlist[hd]->grid[g1]; ; ) { /* g1 lines */
351	gregl	3.6	(*f)(wp);
352	gregl	3.7	if (!--i) break;
353			wp[0][0] += mov[0]; wp[0][1] += mov[1];
354			wp[0][2] += mov[2]; wp[1][0] += mov[0];
355			wp[1][1] += mov[1]; wp[1][2] += mov[2];
356	gregl	3.6	}
357			}
358			}