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/* Copyright (c) 1997 Silicon Graphics, Inc. */
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#ifndef lint
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static char SCCSid[] = "$SunId$ SGI";
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#endif
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/*
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* Holodeck beam support for display process
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*/
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#include "rholo.h"
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#include "rhdisp.h"
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#include "view.h"
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struct cellist {
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GCOORD *cl;
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int n;
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};
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int
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npixels(vp, hr, vr, hp, bi) /* compute appropriate number to evaluate */
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VIEW *vp;
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int hr, vr;
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HOLO *hp;
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int bi;
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{
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static VIEW vdo, vlast;
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static HOLO *hplast;
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GCOORD gc[2];
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FVECT cp[4];
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FVECT ip[4];
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double d;
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register int i;
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/* compute cell corners in image */
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if (!hdbcoord(gc, hp, bi))
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error(CONSISTENCY, "bad beam index in npixels");
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/* has holodeck or view changed? */
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if (hp != hplast || bcmp((char *)vp, (char *)&vlast, sizeof(VIEW))) {
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copystruct(&vdo, vp);
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if (sect_behind(hp, &vdo)) { /* reverse view sense */
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vdo.vdir[0] = -vdo.vdir[0];
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vdo.vdir[1] = -vdo.vdir[1];
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vdo.vdir[2] = -vdo.vdir[2];
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setview(&vdo);
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}
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hplast = hp;
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copystruct(&vlast, vp);
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}
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hdcell(cp, hp, gc+1); /* find cell on image */
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for (i = 0; i < 4; i++) {
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viewloc(ip[i], &vdo, cp[i]);
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if (ip[i][2] < 0.)
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return(0);
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ip[i][0] *= (double)hr; /* scale by resolution */
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ip[i][1] *= (double)vr;
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}
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/* compute quad area */
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d = (ip[1][0]-ip[0][0])*(ip[2][1]-ip[0][1]) -
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(ip[2][0]-ip[0][0])*(ip[1][1]-ip[0][1]);
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d += (ip[2][0]-ip[3][0])*(ip[1][1]-ip[3][1]) -
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(ip[1][0]-ip[3][0])*(ip[2][1]-ip[3][1]);
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if (d < 0)
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d = -d;
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/* round off result */
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return((int)(.5*d+.5));
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}
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/*
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* The ray directions that define the pyramid in visit_cells() needn't
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* be normalized, but they must be given in clockwise order as seen
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* from the pyramid's apex (origin).
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*/
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int
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visit_cells(orig, pyrd, hp, vf, dp) /* visit cells within a pyramid */
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FVECT orig, pyrd[4]; /* pyramid ray directions in clockwise order */
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HOLO *hp;
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int (*vf)();
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char *dp;
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{
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int n = 0;
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int inflags = 0;
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FVECT gp, pn[4], lo, ld;
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double po[4], lbeg, lend, d, t;
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GCOORD gc;
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register int i;
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/* figure out whose side we're on */
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hdgrid(gp, hp, orig);
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for (i = 0; i < 3; i++) {
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inflags |= (gp[i] > FTINY) << (i<<1);
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inflags |= (gp[i] < hp->grid[i]-FTINY) << (i<<1 | 1);
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}
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/* compute pyramid planes */
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for (i = 0; i < 4; i++) {
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fcross(pn[i], pyrd[i], pyrd[(i+1)&03]);
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po[i] = DOT(pn[i], orig);
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}
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/* traverse each wall */
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for (gc.w = 0; gc.w < 6; gc.w++) {
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if (!(inflags & 1<<gc.w)) /* origin on wrong side */
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continue;
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/* scanline algorithm */
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for (gc.i[1] = hp->grid[((gc.w>>1)+2)%3]; gc.i[1]--; ) {
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/* compute scanline */
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gp[gc.w>>1] = gc.w&1 ? hp->grid[gc.w>>1] : 0;
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gp[((gc.w>>1)+1)%3] = 0;
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gp[((gc.w>>1)+2)%3] = gc.i[1] + 0.5;
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hdworld(lo, hp, gp);
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gp[((gc.w>>1)+1)%3] = 1;
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hdworld(ld, hp, gp);
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ld[0] -= lo[0]; ld[1] -= lo[1]; ld[2] -= lo[2];
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/* find scanline limits */
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lbeg = 0; lend = hp->grid[((gc.w>>1)+1)%3];
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for (i = 0; i < 4; i++) {
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t = DOT(pn[i], lo) - po[i];
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d = -DOT(pn[i], ld);
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if (d > FTINY) { /* <- plane */
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if ((t /= d) < lend)
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lend = t;
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} else if (d < -FTINY) { /* plane -> */
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if ((t /= d) > lbeg)
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lbeg = t;
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} else if (t < 0) { /* outside */
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lend = -1;
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break;
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}
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}
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if (lbeg >= lend)
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continue;
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i = lend + .5; /* visit cells on this scan */
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for (gc.i[0] = lbeg + .5; gc.i[0] < i; gc.i[0]++)
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n += (*vf)(&gc, dp);
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}
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}
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return(n);
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}
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sect_behind(hp, vp) /* check if section is "behind" viewpoint */
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register HOLO *hp;
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register VIEW *vp;
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{
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FVECT hcent;
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/* compute holodeck section center */
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VSUM(hcent, hp->orig, hp->xv[0], 0.5);
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VSUM(hcent, hcent, hp->xv[1], 0.5);
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VSUM(hcent, hcent, hp->xv[2], 0.5);
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/* behind if center is behind */
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return(DOT(vp->vdir,hcent) < DOT(vp->vdir,vp->vp));
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}
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viewpyramid(org, dir, hp, vp) /* compute view pyramid */
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FVECT org, dir[4];
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HOLO *hp;
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VIEW *vp;
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{
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register int i;
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/* check view type */
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if (vp->type == VT_PAR)
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return(0);
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/* in front or behind? */
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if (!sect_behind(hp, vp)) {
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if (viewray(org, dir[0], vp, 0., 0.) < -FTINY)
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return(0);
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if (viewray(org, dir[1], vp, 0., 1.) < -FTINY)
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return(0);
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if (viewray(org, dir[2], vp, 1., 1.) < -FTINY)
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return(0);
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if (viewray(org, dir[3], vp, 1., 0.) < -FTINY)
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return(0);
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return(1);
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} /* reverse pyramid */
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if (viewray(org, dir[3], vp, 0., 0.) < -FTINY)
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return(0);
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if (viewray(org, dir[2], vp, 0., 1.) < -FTINY)
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return(0);
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if (viewray(org, dir[1], vp, 1., 1.) < -FTINY)
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return(0);
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if (viewray(org, dir[0], vp, 1., 0.) < -FTINY)
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return(0);
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for (i = 0; i < 3; i++) {
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dir[0][i] = -dir[0][i];
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dir[1][i] = -dir[1][i];
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dir[2][i] = -dir[2][i];
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dir[3][i] = -dir[3][i];
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}
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return(-1);
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}
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int
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addcell(gcp, cl) /* add a cell to a list */
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GCOORD *gcp;
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register struct cellist *cl;
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{
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copystruct(cl->cl+cl->n, gcp);
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cl->n++;
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return(1);
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}
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int
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cellcmp(gcp1, gcp2) /* visit_cells() cell ordering */
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register GCOORD *gcp1, *gcp2;
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{
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register int c;
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if ((c = gcp1->w - gcp2->w))
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return(c);
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if ((c = gcp2->i[1] - gcp1->i[1])) /* wg1 is reverse-ordered */
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return(c);
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return(gcp1->i[0] - gcp2->i[0]);
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}
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GCOORD *
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getviewcells(np, hp, vp) /* get ordered cell list for section view */
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int *np; /* returned number of cells (negative if reversed) */
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register HOLO *hp;
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VIEW *vp;
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{
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FVECT org, dir[4];
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int orient;
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struct cellist cl;
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/* compute view pyramid */
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*np = 0;
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orient = viewpyramid(org, dir, hp, vp);
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if (!orient)
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return(NULL);
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/* allocate enough list space */
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cl.n = 2*( hp->grid[0]*hp->grid[1] +
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hp->grid[0]*hp->grid[2] +
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hp->grid[1]*hp->grid[2] );
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cl.cl = (GCOORD *)malloc(cl.n*sizeof(GCOORD));
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if (cl.cl == NULL)
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goto memerr;
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cl.n = 0; /* add cells within pyramid */
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visit_cells(org, dir, hp, addcell, &cl);
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if (!cl.n) {
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free((char *)cl.cl);
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return(NULL);
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}
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*np = cl.n * orient;
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#if 0
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/* We're just going to free this memory in a moment, and list is
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* sorted automatically by visit_cells(), so we don't need this.
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*/
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/* optimize memory use */
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cl.cl = (GCOORD *)realloc((char *)cl.cl, cl.n*sizeof(GCOORD));
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if (cl.cl == NULL)
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goto memerr;
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/* sort the list */
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qsort((char *)cl.cl, cl.n, sizeof(GCOORD), cellcmp);
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#endif
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return(cl.cl);
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memerr:
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error(SYSTEM, "out of memory in getviewcells");
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}
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