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