Box.cxx

   1 #include "Box.hxx"
   2 #include "InfinitePlane.hxx"
   3
   4 Box::Box() : m_min(Infinity, Infinity, Infinity),
   5   m_max(-Infinity, -Infinity, -Infinity)
   6 {
   7 }
   8
   9 Box::Box(Vec3f min, Vec3f max) : m_min(min), m_max(max)
  10 {
  11 }
  12
  13 Box::~Box()
  14 {
  15 }
  16
  17 Box::Box(const Box& b)
  18 {
  19   m_min = b.m_min;
  20   m_max = b.m_max;
  21 }
  22
  23 Box&
  24 Box::operator=(const Box& b)
  25 {
  26   m_min = b.m_min;
  27   m_max = b.m_max;
  28   return *this;
  29 }
  30
  31 void
  32 Box::Clear()
  33 {
  34 }
  35
  36 void
  37 Box::Extend(const Vec3f& a)
  38 {
  39   // for all three coordinates, move m_max or m_min to the point
  40   for(size_t i = 0; i < 3; i++) {
  41     if(a[i] > m_max[i]) {
  42       m_max[i] = a[i];
  43     } else if(a[i] < m_min[i]) {
  44       m_min[i] = a[i];
  45     } // else: do nothing, coordinate is inside the box
  46   }
  47 }
  48
  49 void
  50 Box::Extend(const Box& box)
  51 {
  52 }
  53
  54 bool
  55 Box::Overlaps(const Box& b) const
  56 {
  57   return false;
  58 }
  59
  60 void
  61 Box::Clip(const Ray& ray, float& tnear, float& tfar) const
  62 {
  63   // Note: equations here are the same as in InfinitePlane::Intersect()
  64   // t = ((o-a)*n) / (d*n)
  65   // o = ray.origin(), d = ray.direction(),
  66   // n = surface normal of plane, a = anchor point of plane
  67   Vec3f diff_min = m_min - ray.origin(); // o-a
  68   Vec3f diff_max = m_max - ray.origin();
  69
  70   float cos_theta, temp;
  71   float tx_near = -Infinity, tx_far = Infinity,
  72     ty_near = -Infinity, ty_far = Infinity,
  73     tz_near = -Infinity, tz_far = Infinity;
  74
  75   // clip along x axis
  76   if((cos_theta = ray.direction().dot(Vec3f(1,0,0))) != 0) // if not parallel...
  77     tx_near = diff_min.dot(Vec3f(1,0,0)) / cos_theta;
  78   if((cos_theta = ray.direction().dot(Vec3f(1,0,0))) != 0)
  79     tx_far = diff_max.dot(Vec3f(1,0,0)) / cos_theta;
  80
  81   // we don't know which is nearer, m_min or m_max, so swap them if neccessary
  82   if(tx_near > tx_far) {
  83     temp = tx_near;
  84     tx_near = tx_far;
  85     tx_far = temp;
  86   }
  87
  88   // do the same for y axis
  89   if((cos_theta = ray.direction().dot(Vec3f(0,1,0))) != 0)
  90     ty_near = diff_min.dot(Vec3f(0,1,0)) / cos_theta;
  91   if((cos_theta = ray.direction().dot(Vec3f(0,1,0))) != 0)
  92     ty_far = diff_max.dot(Vec3f(0,1,0)) / cos_theta;
  93   if(ty_near > ty_far) {
  94     temp = ty_near;
  95     ty_near = ty_far;
  96     ty_far = temp;
  97   }
  98
  99   // ...and for z axis
 100   if((cos_theta = ray.direction().dot(Vec3f(0,0,1))) != 0)
 101     tz_near = diff_min.dot(Vec3f(0,0,1)) / cos_theta;
 102   if((cos_theta = ray.direction().dot(Vec3f(0,0,1))) != 0)
 103     tz_far = diff_max.dot(Vec3f(0,0,1)) / cos_theta;
 104   if(tz_near > tz_far) {
 105     temp = tz_near;
 106     tz_near = tz_far;
 107     tz_far = temp;
 108   }
 109
 110   // now the maximum of "near"s is the entry point of the ray, the minimum
 111   // of "far"s is the ray's exit point. Visually speaking: the ray must cross
 112   // all three "near" planes before it can be inside the box.
 113   // Note: If t_near_max > t_far_min, the ray does not intersect the box
 114   tnear = fmax(fmax(tx_near, ty_near), tz_near);
 115   tfar = fmin(fmin(tx_far, ty_far), tz_far);
 116 }
 117
 118 const Vec3f&
 119 Box::min() const
 120 {
 121   return m_min;
 122 }
 123
 124 const Vec3f&
 125 Box::max() const
 126 {
 127   return m_max;
 128 }