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class HitRecord
def initialize(point, t, ray, out_normal, material)
@point = point
@t = t
front_face = ray.direction.dot(out_normal) < 0
@normal = front_face ? out_normal : -out_normal
@material = material
end
attr_accessor :point, :normal, :t, :material
end
class Hittable
def hit(ray, trange)
nil
end
end
class Hittables < Hittable
def initialize
clear
end
def clear
@objects = []
end
def <<(object)
@objects << object
end
def hit(ray, trange)
rec = nil
closest = trange.max
@objects.each do |object|
if trec = object.hit(ray, Interval.new(trange.min, closest))
rec = trec
closest = trec.t
end
end
rec
end
end
class Sphere < Hittable
def initialize(ox, oy, oz, radius = 1, material)
@centre = Point.new(ox, oy, oz)
@radius = radius
@material = material
end
attr_reader :centre, :radius
def hit(ray, trange)
oc = @centre - ray.origin
a = ray.direction.mag_sqr
h = ray.direction.dot(oc)
c = oc.mag_sqr - @radius ** 2
disc = h ** 2 - a * c
return nil if disc < 0
sqrtd = disc ** 0.5
root = (h - sqrtd) / a
if !trange.surround?(root)
root = (h + sqrtd) / a
if !trange.surround?(root)
return nil
end
end
t = root
p = ray.at(t)
o_n = (p - @centre) / @radius
HitRecord.new(p, t, ray, o_n, @material)
end
end
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