SpotLight.cxx

   1 #include "SpotLight.hxx"
   2
   3 SpotLight::SpotLight(Scene* scene,
   4                      const Vec3f& pos,
   5                      const Vec3f& dir,
   6                      const Vec3f& intensity,
   7                      float alpha_min, // in degree
   8                      float alpha_max) // in degree
   9   : Light(scene),
  10     m_pos(pos),
  11     m_dir(dir),
  12     m_intensity(intensity),
  13     m_alpha_min(alpha_min),
  14     m_alpha_max(alpha_max)
  15 {
  16   m_dir.normalize();
  17 }
  18
  19 SpotLight::~SpotLight()
  20 {
  21 }
  22
  23 SpotLight::SpotLight()
  24   : Light(0),
  25     m_pos(Vec3f()),
  26     m_dir(Vec3f()),
  27     m_intensity(Vec3f()),
  28     m_alpha_min(0.0f),
  29     m_alpha_max(0.0f)
  30 {
  31 }
  32
  33 bool
  34 SpotLight::Illuminate(Ray& shadow_ray, Vec3f& intensity)
  35 {
  36   // direction vector from light source to surface point
  37   Vec3f D = shadow_ray.origin()-m_pos;
  38   D.normalize();
  39   // angle between light source dir and shadow ray dir
  40   float phi = fabs(acos(D.dot(m_dir))*180/M_PI);
  41
  42   // outside cone
  43   if(phi > m_alpha_max)
  44     {
  45       return false;
  46     }
  47   else
  48     {
  49       Vec3f dir = m_pos-shadow_ray.origin();
  50       float r = dir.norm()-Epsilon;
  51       float falloff = 1.0f/(r*r); // falloff for distance
  52
  53       // modify ray for shadow computation
  54       shadow_ray.setHit(0);
  55       // for shadow calculation
  56       shadow_ray.setT(r);
  57       // set direction to light source
  58       dir.normalize();
  59       shadow_ray.setDir(dir);
  60
  61       if(phi < m_alpha_min)
  62         {
  63           intensity = m_intensity * falloff;
  64         }
  65       else
  66         {
  67           // linear falloff from 1 at alpha_min to 0 at alpha_max
  68           float partial = 1.0f-(phi-m_alpha_min)/(m_alpha_max-m_alpha_min);
  69           intensity = m_intensity * falloff * partial;
  70
  71         }
  72       return true;
  73     }
  74   return true;
  75 }
  76
  77 const Vec3f&
  78 SpotLight::position() const
  79 {
  80   return m_pos;
  81 }
  82
  83 const Vec3f&
  84 SpotLight::direction() const
  85 {
  86   return m_dir;
  87 }
  88
  89 bool
  90 SpotLight::IsArea()
  91 {
  92   return false;
  93 }