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74 lines
2 KiB
C++
74 lines
2 KiB
C++
// This file is part of libigl, a simple c++ geometry processing library.
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//
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// Copyright (C) 2014 Alec Jacobson <alecjacobson@gmail.com>
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//
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// This Source Code Form is subject to the terms of the Mozilla Public License
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// v. 2.0. If a copy of the MPL was not distributed with this file, You can
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// obtain one at http://mozilla.org/MPL/2.0/.
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#include "ray_sphere_intersect.h"
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template <
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typename Derivedo,
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typename Derivedd,
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typename Derivedc,
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typename r_type,
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typename t_type>
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IGL_INLINE int igl::ray_sphere_intersect(
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const Eigen::PlainObjectBase<Derivedo> & ao,
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const Eigen::PlainObjectBase<Derivedd> & d,
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const Eigen::PlainObjectBase<Derivedc> & ac,
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r_type r,
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t_type & t0,
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t_type & t1)
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{
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Eigen::Vector3d o = ao-ac;
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// http://wiki.cgsociety.org/index.php/Ray_Sphere_Intersection
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//Compute A, B and C coefficients
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double a = d.dot(d);
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double b = 2 * d.dot(o);
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double c = o.dot(o) - (r * r);
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//Find discriminant
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double disc = b * b - 4 * a * c;
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// if discriminant is negative there are no real roots, so return
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// false as ray misses sphere
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if (disc < 0)
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{
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return 0;
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}
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// compute q as described above
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double distSqrt = sqrt(disc);
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double q;
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if (b < 0)
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{
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q = (-b - distSqrt)/2.0;
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} else
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{
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q = (-b + distSqrt)/2.0;
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}
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// compute t0 and t1
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t0 = q / a;
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double _t1 = c/q;
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if(_t1 == t0)
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{
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return 1;
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}
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t1 = _t1;
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// make sure t0 is smaller than t1
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if (t0 > t1)
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{
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// if t0 is bigger than t1 swap them around
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double temp = t0;
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t0 = t1;
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t1 = temp;
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}
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return 2;
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}
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#ifdef IGL_STATIC_LIBRARY
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// Explicit template instantiation
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template int igl::ray_sphere_intersect<Eigen::Matrix<double, 3, 1, 0, 3, 1>, Eigen::Matrix<double, 3, 1, 0, 3, 1>, Eigen::Matrix<double, 3, 1, 0, 3, 1>, double, double>(Eigen::PlainObjectBase<Eigen::Matrix<double, 3, 1, 0, 3, 1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<double, 3, 1, 0, 3, 1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<double, 3, 1, 0, 3, 1> > const&, double, double&, double&);
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#endif
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