source/geometry/hypersphere.h

   1 #ifndef MSP_GEOMETRY_HYPERSPHERE_H_
   2 #define MSP_GEOMETRY_HYPERSPHERE_H_
   3
   4 #include <cmath>
   5 #include <stdexcept>
   6 #include <msp/linal/vector.h>
   7 #include "hyperbox.h"
   8 #include "ray.h"
   9 #include "shape.h"
  10 #include "surfacepoint.h"
  11
  12 namespace Msp {
  13 namespace Geometry {
  14
  15 /**
  16 A shape consisting of the points within a specific distance from the origin.
  17 Two- and three-dimensional cases are Circle and Sphere, respectively.
  18 */
  19 template<typename T, unsigned D>
  20 class HyperSphere: public Shape<T, D>
  21 {
  22 private:
  23         T radius;
  24
  25 public:
  26         HyperSphere(): radius(1) { }
  27         explicit HyperSphere(T);
  28
  29         virtual HyperSphere *clone() const;
  30
  31         T get_radius() const { return radius; }
  32
  33         virtual HyperBox<T, D> get_axis_aligned_bounding_box() const;
  34         virtual bool contains(const LinAl::Vector<T, D> &) const;
  35         virtual unsigned get_max_ray_intersections() const { return 2; }
  36         virtual unsigned get_intersections(const Ray<T, D> &, SurfacePoint<T, D> *, unsigned) const;
  37 };
  38
  39 template<typename T, unsigned D>
  40 inline HyperSphere<T, D>::HyperSphere(T r):
  41         radius(r)
  42 {
  43         if(r<=T(0))
  44                 throw std::invalid_argument("HyperSphere::HyperShpere");
  45 }
  46
  47 template<typename T, unsigned D>
  48 inline HyperSphere<T, D> *HyperSphere<T, D>::clone() const
  49 {
  50         return new HyperSphere<T, D>(radius);
  51 }
  52
  53 template<typename T, unsigned D>
  54 inline HyperBox<T, D> HyperSphere<T, D>::get_axis_aligned_bounding_box() const
  55 {
  56         LinAl::Vector<T, D> dimensions;
  57         for(unsigned i=0; i<D; ++i)
  58                 dimensions[i] = radius;
  59         return HyperBox<T, D>(dimensions);
  60 }
  61
  62 template<typename T, unsigned D>
  63 inline bool HyperSphere<T, D>::contains(const LinAl::Vector<T, D> &point) const
  64 {
  65         return inner_product(point, point)<=radius*radius;
  66 }
  67
  68 template<typename T, unsigned D>
  69 inline unsigned HyperSphere<T, D>::get_intersections(const Ray<T, D> &ray, SurfacePoint<T, D> *points, unsigned size) const
  70 {
  71         using std::sqrt;
  72
  73         T mid = -inner_product(ray.get_direction(), ray.get_start());
  74         LinAl::Vector<T, D> nearest = ray.get_start()+ray.get_direction()*mid;
  75         T offset_sq = radius*radius-inner_product(nearest, nearest);
  76         if(offset_sq<0)
  77                 return 0;
  78         T offset = sqrt(offset_sq);
  79
  80         unsigned n = 0;
  81         for(int i=-1; (n<size && i<=1); i+=2)
  82         {
  83                 T x = mid+offset*i;
  84                 if(ray.check_limits(x))
  85                 {
  86                         if(points)
  87                         {
  88                                 points[n].position = ray.get_start()+ray.get_direction()*x;
  89                                 points[n].normal = normalize(points[n].position);
  90                                 points[n].distance = x;
  91                         }
  92
  93                         ++n;
  94                 }
  95         }
  96
  97         return n;
  98 }
  99
 100 } // namespace Geometry
 101 } // namespace Msp
 102
 103 #endif