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cs440-acg/ext/openexr/IlmBase/Imath/ImathSphere.h

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+///////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2002-2012, Industrial Light & Magic, a division of Lucas
+// Digital Ltd. LLC
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+// *       Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// *       Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+// *       Neither the name of Industrial Light & Magic nor the names of
+// its contributors may be used to endorse or promote products derived
+// from this software without specific prior written permission. 
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+///////////////////////////////////////////////////////////////////////////
+
+
+
+#ifndef INCLUDED_IMATHSPHERE_H
+#define INCLUDED_IMATHSPHERE_H
+
+//-------------------------------------
+//
+//	A 3D sphere class template
+//
+//-------------------------------------
+
+#include "ImathVec.h"
+#include "ImathBox.h"
+#include "ImathLine.h"
+#include "ImathNamespace.h"
+
+IMATH_INTERNAL_NAMESPACE_HEADER_ENTER
+
+template <class T>
+class Sphere3
+{
+  public:
+
+    Vec3<T>	center;
+    T           radius;
+
+    //---------------
+    //	Constructors
+    //---------------
+
+    Sphere3() : center(0,0,0), radius(0) {}
+    Sphere3(const Vec3<T> &c, T r) : center(c), radius(r) {}
+
+    //-------------------------------------------------------------------
+    //	Utilities:
+    //
+    //	s.circumscribe(b)	sets center and radius of sphere s
+    //				so that the s tightly encloses box b.
+    //
+    //	s.intersectT (l, t)	If sphere s and line l intersect, then
+    //				intersectT() computes the smallest t,
+    //				t >= 0, so that l(t) is a point on the
+    //				sphere.  intersectT() then returns true.
+    //
+    //				If s and l do not intersect, intersectT()
+    //				returns false.
+    //
+    //	s.intersect (l, i)	If sphere s and line l intersect, then
+    //				intersect() calls s.intersectT(l,t) and
+    //				computes i = l(t).
+    //
+    //				If s and l do not intersect, intersect()
+    //				returns false.
+    //
+    //-------------------------------------------------------------------
+
+    void circumscribe(const Box<Vec3<T> > &box);
+    bool intersect(const Line3<T> &l, Vec3<T> &intersection) const;
+    bool intersectT(const Line3<T> &l, T &t) const;
+};
+
+
+//--------------------
+// Convenient typedefs
+//--------------------
+
+typedef Sphere3<float> Sphere3f;
+typedef Sphere3<double> Sphere3d;
+
+
+//---------------
+// Implementation
+//---------------
+
+template <class T>
+void Sphere3<T>::circumscribe(const Box<Vec3<T> > &box)
+{
+    center = T(0.5) * (box.min + box.max);
+    radius = (box.max - center).length();
+}
+
+
+template <class T>
+bool Sphere3<T>::intersectT(const Line3<T> &line, T &t) const
+{
+    bool doesIntersect = true;
+
+    Vec3<T> v = line.pos - center;
+    T B = T(2.0) * (line.dir ^ v);
+    T C = (v ^ v) - (radius * radius);
+
+    // compute discriminant
+    // if negative, there is no intersection
+
+    T discr = B*B - T(4.0)*C;
+
+    if (discr < 0.0)
+    {
+	// line and Sphere3 do not intersect
+
+	doesIntersect = false;
+    }
+    else
+    {
+	// t0: (-B - sqrt(B^2 - 4AC)) / 2A  (A = 1)
+
+	T sqroot = Math<T>::sqrt(discr);
+	t = (-B - sqroot) * T(0.5);
+
+	if (t < 0.0)
+	{
+	    // no intersection, try t1: (-B + sqrt(B^2 - 4AC)) / 2A  (A = 1)
+
+	    t = (-B + sqroot) * T(0.5);
+	}
+
+	if (t < 0.0)
+	    doesIntersect = false;
+    }
+
+    return doesIntersect;
+}
+
+
+template <class T>
+bool Sphere3<T>::intersect(const Line3<T> &line, Vec3<T> &intersection) const
+{
+    T t;
+
+    if (intersectT (line, t))
+    {
+	intersection = line(t);
+	return true;
+    }
+    else
+    {
+	return false;
+    }
+}
+
+IMATH_INTERNAL_NAMESPACE_HEADER_EXIT
+
+#endif // INCLUDED_IMATHSPHERE_H