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#ifndef lint
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static const char RCSid[] = "$Id: o_cone.c,v 2.2 2003/02/22 02:07:26 greg Exp $";
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#endif
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/*
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* o_cone.c - routines for intersecting cubes with cones.
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*
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* 2/3/86
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*/
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#include "standard.h"
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#include "octree.h"
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#include "object.h"
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#include "cone.h"
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#define ROOT3 1.732050808
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/*
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* The algorithm used to detect cube intersection with cones is
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* recursive. First, we approximate the cube to be a sphere. Then
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* we test for cone intersection with the sphere by testing the
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* segment of the cone which is nearest the sphere's center.
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* If the cone has points within the cube's bounding sphere,
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* we must check for intersection with the cube. This is done with
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* the 3D line clipper. The same cone segment is used in this test.
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* If the clip fails, we still cannot be sure there is no intersection,
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* so we subdivide the cube and recurse.
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* If none of the sub-cubes intersect, then our cube does not intersect.
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*/
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extern double mincusize; /* minimum cube size */
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static double findcseg(FVECT ep0, FVECT ep1, CONE *co, FVECT p);
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/* XXX o_cone() is extern, but not declared in any header file */
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int
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o_cone( /* determine if cone intersects cube */
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OBJREC *o,
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register CUBE *cu
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)
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{
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CONE *co;
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FVECT ep0, ep1;
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#ifdef STRICT
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FVECT cumin, cumax;
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CUBE cukid;
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register int j;
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#endif
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double r;
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FVECT p;
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register int i;
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/* get cone arguments */
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co = getcone(o, 0);
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/* get cube center */
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r = cu->cusize * 0.5;
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for (i = 0; i < 3; i++)
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p[i] = cu->cuorg[i] + r;
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r *= ROOT3; /* bounding radius for cube */
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if (findcseg(ep0, ep1, co, p) > 0.0) {
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/* check min. distance to cone */
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if (dist2lseg(p, ep0, ep1) > (r+FTINY)*(r+FTINY))
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return(O_MISS);
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#ifdef STRICT
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/* get cube boundaries */
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for (i = 0; i < 3; i++)
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cumax[i] = (cumin[i] = cu->cuorg[i]) + cu->cusize;
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/* closest segment intersects? */
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if (clip(ep0, ep1, cumin, cumax))
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return(O_HIT);
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}
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/* check sub-cubes */
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cukid.cusize = cu->cusize * 0.5;
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if (cukid.cusize < mincusize)
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return(O_HIT); /* cube too small */
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cukid.cutree = EMPTY;
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for (j = 0; j < 8; j++) {
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for (i = 0; i < 3; i++) {
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cukid.cuorg[i] = cu->cuorg[i];
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if (1<<i & j)
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cukid.cuorg[i] += cukid.cusize;
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}
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if (o_cone(o, &cukid))
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return(O_HIT); /* sub-cube intersects */
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}
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return(O_MISS); /* no intersection */
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#else
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}
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return(O_HIT); /* assume intersection */
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#endif
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}
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static double
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findcseg( /* find line segment from cone closest to p */
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FVECT ep0,
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FVECT ep1,
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register CONE *co,
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FVECT p
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)
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{
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double d;
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FVECT v;
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register int i;
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/* find direction from axis to point */
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for (i = 0; i < 3; i++)
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v[i] = p[i] - CO_P0(co)[i];
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d = DOT(v, co->ad);
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for (i = 0; i < 3; i++)
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v[i] = v[i] - d*co->ad[i];
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d = normalize(v);
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if (d > 0.0) /* find endpoints of segment */
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for (i = 0; i < 3; i++) {
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ep0[i] = CO_R0(co)*v[i] + CO_P0(co)[i];
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ep1[i] = CO_R1(co)*v[i] + CO_P1(co)[i];
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}
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return(d); /* return distance from axis */
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}
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