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greg |
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/* Copyright (c) 1986 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_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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o_cone(o, cu) /* 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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double dist2lseg(), findcseg(); |
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CONE *co; |
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FVECT ep0, ep1; |
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FVECT cumin, cumax; |
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CUBE cukid; |
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double r; |
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FVECT p; |
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register int i, j; |
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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(0); |
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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(1); |
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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(1); /* 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(1); /* sub-cube intersects */ |
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} |
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return(0); /* no intersection */ |
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#else |
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} |
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return(1); /* assume intersection */ |
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#endif |
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} |
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double |
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findcseg(ep0, ep1, co, p) /* find line segment from cone closest to p */ |
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FVECT ep0, ep1; |
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register CONE *co; |
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FVECT p; |
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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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} |
