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root/radiance/ray/src/ot/sphere.c
Revision: 2.2
Committed: Sat Feb 22 02:07:26 2003 UTC (21 years, 1 month ago) by greg
Content type: text/plain
Branch: MAIN
CVS Tags: rad3R5
Changes since 2.1: +1 -4 lines
Log Message:
Changes and check-in for 3.5 release
Includes new source files and modifications not recorded for many years
See ray/doc/notes/ReleaseNotes for notes between 3.1 and 3.5 release

File Contents

# User Rev Content
1 greg 1.1 #ifndef lint
2 greg 2.2 static const char RCSid[] = "$Id$";
3 greg 1.1 #endif
4     /*
5     * sphere.c - routines for creating octrees for spheres.
6     *
7     * 7/28/85
8     */
9    
10     #include "standard.h"
11    
12     #include "octree.h"
13    
14     #include "object.h"
15    
16     #include "otypes.h"
17    
18     #define ROOT3 1.732050808
19    
20     /*
21     * Regrettably, the algorithm for determining a cube's location
22     * with respect to a sphere is not simple. First, a quick test is
23     * made to determine if the sphere and the bounding sphere of the cube
24     * are disjoint. This of course means no intersection. Failing this,
25     * we determine if the cube lies inside the sphere. The cube is
26     * entirely inside if the bounding sphere on the cube is
27     * contained within our sphere. This means no intersection. Otherwise,
28     * if the cube radius is smaller than the sphere's and the cube center is
29     * inside the sphere, we assume intersection. If these tests fail,
30     * we proceed as follows.
31     * The sphere center is located in relation to the 6 cube faces,
32     * and one of four things is done depending on the number of
33     * planes the center lies between:
34     *
35     * 0: The sphere is closest to a cube corner, find the
36     * distance to that corner.
37     *
38     * 1: The sphere is closest to a cube edge, find this
39     * distance.
40     *
41     * 2: The sphere is closest to a cube face, find the distance.
42     *
43     * 3: The sphere has its center inside the cube.
44     *
45     * In cases 0-2, if the closest part of the cube is within
46     * the radius distance from the sphere center, we have intersection.
47     * If it is not, the cube must be outside the sphere.
48     * In case 3, there must be intersection, and no further
49     * tests are necessary.
50     */
51    
52    
53     o_sphere(o, cu) /* determine if sphere intersects cube */
54     OBJREC *o;
55     register CUBE *cu;
56     {
57     FVECT v1;
58     double d1, d2;
59 greg 1.4 register FLOAT *fa;
60 greg 1.1 register int i;
61     #define cent fa
62     #define rad fa[3]
63     /* get arguments */
64 greg 1.3 if (o->oargs.nfargs != 4)
65     objerror(o, USER, "bad # arguments");
66 greg 1.1 fa = o->oargs.farg;
67 greg 1.3 if (rad < -FTINY) {
68     objerror(o, WARNING, "negative radius");
69     o->otype = o->otype == OBJ_SPHERE ?
70     OBJ_BUBBLE : OBJ_SPHERE;
71     rad = -rad;
72     } else if (rad <= FTINY)
73     objerror(o, USER, "zero radius");
74 greg 1.1
75     d1 = ROOT3/2.0 * cu->cusize; /* bounding radius for cube */
76    
77     d2 = cu->cusize * 0.5; /* get distance between centers */
78     for (i = 0; i < 3; i++)
79     v1[i] = cu->cuorg[i] + d2 - cent[i];
80     d2 = DOT(v1,v1);
81    
82     if (d2 > (rad+d1+FTINY)*(rad+d1+FTINY)) /* quick test */
83 greg 1.2 return(O_MISS); /* cube outside */
84 greg 1.1
85     /* check sphere interior */
86     if (d1 < rad) {
87     if (d2 < (rad-d1-FTINY)*(rad-d1-FTINY))
88 greg 1.2 return(O_MISS); /* cube inside sphere */
89 greg 1.1 if (d2 < (rad+FTINY)*(rad+FTINY))
90 greg 1.2 return(O_HIT); /* cube center inside */
91 greg 1.1 }
92     /* find closest distance */
93     for (i = 0; i < 3; i++)
94     if (cent[i] < cu->cuorg[i])
95     v1[i] = cu->cuorg[i] - cent[i];
96     else if (cent[i] > cu->cuorg[i] + cu->cusize)
97     v1[i] = cent[i] - (cu->cuorg[i] + cu->cusize);
98     else
99     v1[i] = 0;
100     /* final intersection check */
101     if (DOT(v1,v1) <= (rad+FTINY)*(rad+FTINY))
102 greg 1.2 return(O_HIT);
103 greg 1.1 else
104 greg 1.2 return(O_MISS);
105 greg 1.1 }