source: NonGTP/OpenEXR/include/Imath/ImathSphere.h @ 855

Revision 855, 4.6 KB checked in by igarcia, 19 years ago (diff)
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[855]1///////////////////////////////////////////////////////////////////////////
2//
3// Copyright (c) 2002, Industrial Light & Magic, a division of Lucas
4// Digital Ltd. LLC
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33///////////////////////////////////////////////////////////////////////////
34
35
36
37#ifndef INCLUDED_IMATHSPHERE_H
38#define INCLUDED_IMATHSPHERE_H
39
40//-------------------------------------
41//
42//      A 3D sphere class template
43//
44//-------------------------------------
45
46#include <ImathVec.h>
47#include <ImathBox.h>
48#include <ImathLine.h>
49
50namespace Imath {
51
52template <class T>
53class Sphere3
54{
55  public:
56
57    Vec3<T>     center;
58    T           radius;
59
60    //---------------
61    //  Constructors
62    //---------------
63
64    Sphere3() : center(0,0,0), radius(0) {}
65    Sphere3(const Vec3<T> &c, T r) : center(c), radius(r) {}
66
67    //-------------------------------------------------------------------
68    //  Utilities:
69    //
70    //  s.circumscribe(b)       sets center and radius of sphere s
71    //                          so that the s tightly encloses box b.
72    //
73    //  s.intersectT (l, t)     If sphere s and line l intersect, then
74    //                          intersectT() computes the smallest t,
75    //                          t >= 0, so that l(t) is a point on the
76    //                          sphere.  intersectT() then returns true.
77    //
78    //                          If s and l do not intersect, intersectT()
79    //                          returns false.
80    //
81    //  s.intersect (l, i)      If sphere s and line l intersect, then
82    //                          intersect() calls s.intersectT(l,t) and
83    //                          computes i = l(t).
84    //
85    //                          If s and l do not intersect, intersect()
86    //                          returns false.
87    //
88    //-------------------------------------------------------------------
89
90    void circumscribe(const Box<Vec3<T> > &box);
91    bool intersect(const Line3<T> &l, Vec3<T> &intersection) const;
92    bool intersectT(const Line3<T> &l, T &t) const;
93};
94
95
96//--------------------
97// Convenient typedefs
98//--------------------
99
100typedef Sphere3<float> Sphere3f;
101typedef Sphere3<double> Sphere3d;
102
103
104//---------------
105// Implementation
106//---------------
107
108template <class T>
109void Sphere3<T>::circumscribe(const Box<Vec3<T> > &box)
110{
111    center = T(0.5) * (box.min + box.max);
112    radius = (box.max - center).length();
113}
114
115
116template <class T>
117bool Sphere3<T>::intersectT(const Line3<T> &line, T &t) const
118{
119    bool doesIntersect = true;
120
121    Vec3<T> v = line.pos - center;
122    T B = 2.0 * (line.dir ^ v);
123    T C = (v ^ v) - (radius * radius);
124
125    // compute discriminant
126    // if negative, there is no intersection
127
128    T discr = B*B - 4.0*C;
129
130    if (discr < 0.0)
131    {
132        // line and Sphere3 do not intersect
133
134        doesIntersect = false;
135    }
136    else
137    {
138        // t0: (-B - sqrt(B^2 - 4AC)) / 2A  (A = 1)
139
140        T sqroot = Math<T>::sqrt(discr);
141        t = (-B - sqroot) * 0.5;
142
143        if (t < 0.0)
144        {
145            // no intersection, try t1: (-B + sqrt(B^2 - 4AC)) / 2A  (A = 1)
146
147            t = (-B + sqroot) * 0.5;
148        }
149
150        if (t < 0.0)
151            doesIntersect = false;
152    }
153
154    return doesIntersect;
155}
156
157
158template <class T>
159bool Sphere3<T>::intersect(const Line3<T> &line, Vec3<T> &intersection) const
160{
161    T t;
162
163    if (intersectT (line, t))
164    {
165        intersection = line(t);
166        return true;
167    }
168    else
169    {
170        return false;
171    }
172}
173
174
175} //namespace Imath
176
177#endif
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