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/* Copyright (c) 1988 Regents of the University of California */
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#ifndef lint
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static char SCCSid[] = "$SunId$ LBL";
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#endif
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/*
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* o_instance.c - routines for creating octrees for other octrees.
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*
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* 11/11/88
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*/
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#include "standard.h"
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#include "object.h"
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#include "instance.h"
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#include "plocate.h"
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/*
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* To determine if two cubes intersect:
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*
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* 1) Check to see if any vertices of first cube are inside the
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* second (intersection).
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*
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* 2) Check to see if all vertices of first are to one side of
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* second (no intersection).
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*
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* 3) Perform 1 and 2 with roles reversed.
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*
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* 4) Check to see if any portion of any edge of second is inside
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* first (intersection).
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*
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* 5) If test 4 fails, we have no intersection.
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*
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* Note that if we were testing two boxes, we would need
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* to check that neither had any edges inside the other to be sure.
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* Since an octree is a volume rather than a surface, we will
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* return a value of 2 if the cube is entirely within the octree.
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*/
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o_instance(o, cu) /* determine if cubes intersect */
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OBJREC *o;
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CUBE *cu;
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{
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static char vstart[4] = {0, 3, 5, 6};
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FVECT cumin, cumax;
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FVECT vert[8];
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FVECT v1, v2;
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register INSTANCE *in;
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int vloc, vout;
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register int i, j;
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/* get octree arguments */
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in = getinstance(o, GET_BOUNDS);
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/* check if cube vertex in octree */
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for (j = 0; j < 3; j++)
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cumax[j] = (cumin[j] = in->obj->scube.cuorg[j]) +
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in->obj->scube.cusize;
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vloc = ABOVE | BELOW;
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vout = 0;
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for (i = 0; i < 8; i++) {
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for (j = 0; j < 3; j++) {
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v1[j] = cu->cuorg[j];
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if (i & 1<<j)
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v1[j] += cu->cusize;
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}
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multp3(v2, v1, in->b.xfm);
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if (j = plocate(v2, cumin, cumax))
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vout++;
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vloc &= j;
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}
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if (vout == 0) /* all inside */
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return(2);
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if (vout < 8) /* some inside */
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return(1);
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if (vloc) /* all to one side */
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return(0);
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/* octree vertices in cube? */
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for (j = 0; j < 3; j++)
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cumax[j] = (cumin[j] = cu->cuorg[j]) + cu->cusize;
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vloc = ABOVE | BELOW;
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for (i = 0; i < 8; i++) {
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for (j = 0; j < 3; j++) {
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v1[j] = in->obj->scube.cuorg[j];
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if (i & 1<<j)
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v1[j] += in->obj->scube.cusize;
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}
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multp3(vert[i], v1, in->f.xfm);
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if (j = plocate(vert[i], cumin, cumax))
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vloc &= j;
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else
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return(1); /* vertex inside */
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}
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if (vloc) /* all to one side */
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return(0);
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/* check edges */
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for (i = 0; i < 4; i++)
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for (j = 0; j < 3; j++) {
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/* clip modifies vertices! */
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VCOPY(v1, vert[vstart[i]]);
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VCOPY(v2, vert[vstart[i] ^ 1<<j]);
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if (clip(v1, v2, cumin, cumax))
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return(1); /* edge inside */
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}
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return(0); /* no intersection */
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}
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