Method: Mittsu::Ray#intersect_box

Defined in:

lib/mittsu/math/ray.rb

#intersect_box(box, target = Mittsu::Vector3.new) ⇒ Object

# File 'lib/mittsu/math/ray.rb', line 192

def intersect_box(box, target = Mittsu::Vector3.new)
  # http:#www.scratchapixel.com/lessons/3d-basic-lessons/lesson-7-intersecting-simple-shapes/ray-box-intersection/
  invdirx = 1.0 / @direction.x
  invdiry = 1.0 / @direction.y
  invdirz = 1.0 / @direction.z
  origin = @origin
  if invdirx >= 0
    tmin = (box.min.x - origin.x) * invdirx
    tmax = (box.max.x - origin.x) * invdirx
  else
    tmin = (box.max.x - origin.x) * invdirx
    tmax = (box.min.x - origin.x) * invdirx
  end
  if invdiry >= 0
    tymin = (box.min.y - origin.y) * invdiry
    tymax = (box.max.y - origin.y) * invdiry
  else
    tymin = (box.max.y - origin.y) * invdiry
    tymax = (box.min.y - origin.y) * invdiry
  end
  return nil if tmin > tymax || tymin > tmax
  # These lines also handle the case where tmin or tmax is NaN
  # (result of 0 * Infinity). x != x returns true if x is NaN
  tmin = tymin if tymin > tmin || tmin != tmin
  tmax = tymax if tymax < tmax || tmax != tmax
  if invdirz >= 0
    tzmin = (box.min.z - origin.z) * invdirz
    tzmax = (box.max.z - origin.z) * invdirz
  else
    tzmin = (box.max.z - origin.z) * invdirz
    tzmax = (box.min.z - origin.z) * invdirz
  end
  return nil if tmin > tzmax || tzmin > tmax
  tmin = tzmin if tzmin > tmin || tmin != tmin
  tmax = tzmax if tzmax < tmax || tmax != tmax
  #return point closest to the ray (positive side)
  return nil if tmax < 0
  self.at(tmin >= 0 ? tmin : tmax, target)
end