source/geometry/halfspace.h

   1 #ifndef MSP_GEOMETRY_HALFSPACE_H_
   2 #define MSP_GEOMETRY_HALFSPACE_H_
   3
   4 #include "shape.h"
   5
   6 namespace Msp {
   7 namespace Geometry {
   8
   9 /**
  10 An unbounded shape consisting of the space on one side of a plane.  Mostly
  11 useful when intersected with other shapes.
  12 */
  13 template<typename T, unsigned D>
  14 class HalfSpace: public Shape<T, D>
  15 {
  16 private:
  17         LinAl::Vector<T, D> normal;
  18
  19 public:
  20         HalfSpace();
  21         HalfSpace(const LinAl::Vector<T, D> &);
  22
  23         virtual HalfSpace *clone() const;
  24
  25         const LinAl::Vector<T, D> &get_normal() const { return normal; }
  26
  27         virtual BoundingBox<T, D> get_axis_aligned_bounding_box() const;
  28         virtual bool contains(const LinAl::Vector<T, D> &) const;
  29         virtual unsigned get_max_ray_intersections() const { return 1; }
  30         virtual unsigned get_intersections(const Ray<T, D> &, SurfacePoint<T, D> *, unsigned) const;
  31         virtual Coverage get_coverage(const BoundingBox<T, D> &) const;
  32 };
  33
  34 template<typename T, unsigned D>
  35 inline HalfSpace<T, D>::HalfSpace()
  36 {
  37         normal[0] = T(1);
  38 }
  39
  40 template<typename T, unsigned D>
  41 inline HalfSpace<T, D>::HalfSpace(const LinAl::Vector<T, D> &n):
  42         normal(normalize(n))
  43 { }
  44
  45 template<typename T, unsigned D>
  46 inline HalfSpace<T, D> *HalfSpace<T, D>::clone() const
  47 {
  48         return new HalfSpace<T, D>(normal);
  49 }
  50
  51 template<typename T, unsigned D>
  52 inline BoundingBox<T, D> HalfSpace<T, D>::get_axis_aligned_bounding_box() const
  53 {
  54         // XXX If the normal is aligned to an axis, should the bounding box reflect that?
  55         return ~BoundingBox<T, D>();
  56 }
  57
  58 template<typename T, unsigned D>
  59 inline bool HalfSpace<T, D>::contains(const LinAl::Vector<T, D> &point) const
  60 {
  61         return inner_product(point, normal)<=T(0);
  62 }
  63
  64 template<typename T, unsigned D>
  65 inline unsigned HalfSpace<T, D>::get_intersections(const Ray<T, D> &ray, SurfacePoint<T, D> *points, unsigned size) const
  66 {
  67         T d = inner_product(ray.get_start(), normal);
  68         T c = inner_product(ray.get_direction(), normal);
  69         if(c==T(0))
  70                 return 0;
  71
  72         T x = -d/c;
  73         if(ray.check_limits(x))
  74         {
  75                 if(points && size>0)
  76                 {
  77                         points[0].position = ray.get_start()+ray.get_direction()*x;
  78                         points[0].normal = normal;
  79                         points[0].distance = x;
  80                         points[0].entry = (c<T(0));
  81                 }
  82
  83                 return 1;
  84         }
  85
  86         return 0;
  87 }
  88
  89 template<typename T, unsigned D>
  90 inline Coverage HalfSpace<T, D>::get_coverage(const BoundingBox<T, D> &bbox) const
  91 {
  92         LinAl::Vector<T, D> low_point;
  93         LinAl::Vector<T, D> high_point;
  94         for(unsigned i=0; i<D; ++i)
  95         {
  96                 low_point[i] = (normal[i]>=T(0) ? bbox.get_minimum_coordinate(i) : bbox.get_maximum_coordinate(i));
  97                 high_point[i] = (normal[i]>=T(0) ? bbox.get_maximum_coordinate(i) : bbox.get_minimum_coordinate(i));
  98         }
  99
 100         if(contains(high_point))
 101                 return FULL_COVERAGE;
 102         else if(contains(low_point))
 103                 return PARTIAL_COVERAGE;
 104         else
 105                 return NO_COVERAGE;
 106 }
 107
 108 } // namespace Geometry
 109 } // namespace Msp
 110
 111 #endif