1 |
/* Copyright (c) 1986 Regents of the University of California */ |
2 |
|
3 |
#ifndef lint |
4 |
static char SCCSid[] = "$SunId$ LBL"; |
5 |
#endif |
6 |
|
7 |
/* |
8 |
* o_cone.c - routines for intersecting cubes with cones. |
9 |
* |
10 |
* 2/3/86 |
11 |
*/ |
12 |
|
13 |
#include "standard.h" |
14 |
|
15 |
#include "octree.h" |
16 |
|
17 |
#include "object.h" |
18 |
|
19 |
#include "cone.h" |
20 |
|
21 |
#define ROOT3 1.732050808 |
22 |
|
23 |
/* |
24 |
* The algorithm used to detect cube intersection with cones is |
25 |
* recursive. First, we approximate the cube to be a sphere. Then |
26 |
* we test for cone intersection with the sphere by testing the |
27 |
* segment of the cone which is nearest the sphere's center. |
28 |
* If the cone has points within the cube's bounding sphere, |
29 |
* we must check for intersection with the cube. This is done with |
30 |
* the 3D line clipper. The same cone segment is used in this test. |
31 |
* If the clip fails, we still cannot be sure there is no intersection, |
32 |
* so we subdivide the cube and recurse. |
33 |
* If none of the sub-cubes intersect, then our cube does not intersect. |
34 |
*/ |
35 |
|
36 |
extern double mincusize; /* minimum cube size */ |
37 |
|
38 |
|
39 |
o_cone(o, cu) /* determine if cone intersects cube */ |
40 |
OBJREC *o; |
41 |
register CUBE *cu; |
42 |
{ |
43 |
double dist2lseg(), findcseg(); |
44 |
CONE *co; |
45 |
FVECT ep0, ep1; |
46 |
FVECT cumin, cumax; |
47 |
CUBE cukid; |
48 |
double r; |
49 |
FVECT p; |
50 |
register int i, j; |
51 |
/* get cone arguments */ |
52 |
co = getcone(o, 0); |
53 |
/* get cube center */ |
54 |
r = cu->cusize * 0.5; |
55 |
for (i = 0; i < 3; i++) |
56 |
p[i] = cu->cuorg[i] + r; |
57 |
r *= ROOT3; /* bounding radius for cube */ |
58 |
|
59 |
if (findcseg(ep0, ep1, co, p) > 0.0) { |
60 |
/* check min. distance to cone */ |
61 |
if (dist2lseg(p, ep0, ep1) > (r+FTINY)*(r+FTINY)) |
62 |
return(0); |
63 |
#ifdef STRICT |
64 |
/* get cube boundaries */ |
65 |
for (i = 0; i < 3; i++) |
66 |
cumax[i] = (cumin[i] = cu->cuorg[i]) + cu->cusize; |
67 |
/* closest segment intersects? */ |
68 |
if (clip(ep0, ep1, cumin, cumax)) |
69 |
return(1); |
70 |
} |
71 |
/* check sub-cubes */ |
72 |
cukid.cusize = cu->cusize * 0.5; |
73 |
if (cukid.cusize < mincusize) |
74 |
return(1); /* cube too small */ |
75 |
cukid.cutree = EMPTY; |
76 |
|
77 |
for (j = 0; j < 8; j++) { |
78 |
for (i = 0; i < 3; i++) { |
79 |
cukid.cuorg[i] = cu->cuorg[i]; |
80 |
if (1<<i & j) |
81 |
cukid.cuorg[i] += cukid.cusize; |
82 |
} |
83 |
if (o_cone(o, &cukid)) |
84 |
return(1); /* sub-cube intersects */ |
85 |
} |
86 |
return(0); /* no intersection */ |
87 |
#else |
88 |
} |
89 |
return(1); /* assume intersection */ |
90 |
#endif |
91 |
} |
92 |
|
93 |
|
94 |
double |
95 |
findcseg(ep0, ep1, co, p) /* find line segment from cone closest to p */ |
96 |
FVECT ep0, ep1; |
97 |
register CONE *co; |
98 |
FVECT p; |
99 |
{ |
100 |
double d; |
101 |
FVECT v; |
102 |
register int i; |
103 |
/* find direction from axis to point */ |
104 |
for (i = 0; i < 3; i++) |
105 |
v[i] = p[i] - CO_P0(co)[i]; |
106 |
d = DOT(v, co->ad); |
107 |
for (i = 0; i < 3; i++) |
108 |
v[i] = v[i] - d*co->ad[i]; |
109 |
d = normalize(v); |
110 |
if (d > 0.0) /* find endpoints of segment */ |
111 |
for (i = 0; i < 3; i++) { |
112 |
ep0[i] = CO_R0(co)*v[i] + CO_P0(co)[i]; |
113 |
ep1[i] = CO_R1(co)*v[i] + CO_P1(co)[i]; |
114 |
} |
115 |
return(d); /* return distance from axis */ |
116 |
} |