class Ray
  def initialize(origin = Point.new, direction = Vec3.new)
    @origin = origin
    @direction = direction
  end

  attr_reader :origin, :direction

  def at(time)
    @origin + (@direction * time)
  end

  def colour(world)
    if rec = world.hit(self, Interval.new(0, Float::INFINITY))
      return (Colour.new(1,1,1) + rec.normal) * 0.5
    end

    unit_dir = direction.unit
    a = (unit_dir.y + 1) / 2
    Colour.new(1.0, 1.0, 1.0) * (1-a) + Colour.new(0.5, 0.7, 1.0) * a
  end
end