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