Done C10, Materials

4 files changed, 58 insertions, 11 deletions

diff --git a/lib/hittable.rb b/lib/hittable.rb
index c84764f..facdd14 100644
--- a/lib/hittable.rb
+++ b/lib/hittable.rb
@@ -1,16 +1,13 @@
 class HitRecord
-  def initialize(point, t, ray, out_normal)
+  def initialize(point, t, ray, out_normal, material)
     @point = point
     @t = t
-    set_face_normal(ray, out_normal)
-  end
-
-  attr_accessor :point, :normal, :t
-
-  def set_face_normal(ray, out_normal)
     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
@@ -48,9 +45,10 @@ class Hittables < Hittable
 end
 
 class Sphere < Hittable
-  def initialize(ox, oy, oz, radius = 1)
+  def initialize(ox, oy, oz, radius = 1, material)
     @centre = Point.new(ox, oy, oz)
     @radius = radius
+    @material = material
   end
 
   attr_reader :centre, :radius
@@ -76,6 +74,6 @@ class Sphere < Hittable
     t = root
     p = ray.at(t)
     o_n = (p - @centre) / @radius
-    HitRecord.new(p, t, ray, o_n)
+    HitRecord.new(p, t, ray, o_n, @material)
   end
 end
diff --git a/lib/material.rb b/lib/material.rb
new file mode 100644
index 0000000..c935147
--- /dev/null
+++ b/lib/material.rb
@@ -0,0 +1,38 @@
+class Material
+  def initialize(r, g, b)
+    @albedo = Colour.new(r, g, b)
+  end
+
+  def attenuation
+    @albedo
+  end
+
+  def scatter(ray, record)
+    nil
+  end
+end
+
+class Lambertian < Material
+  def scatter(ray, record)
+    scat = record.normal + Vec3.random_unit
+    scat = rec.normal if scat.near_zero?
+    Ray.new(record.point, scat)
+  end
+end
+
+class Metal < Material
+  def initialize(r, g, b, fuzz)
+    @fuzz = fuzz < 1 ? fuzz : 1
+    super(r, g, b)
+  end
+
+  def scatter(ray, record)
+    refl = ray.direction.reflect(record.normal)
+    refl = refl.unit + (Vec3.random_unit * @fuzz)
+    if refl.dot(record.normal) > 0
+      Ray.new(record.point, refl)
+    else
+      nil
+    end
+  end
+end
diff --git a/lib/ray.rb b/lib/ray.rb
index eb6038c..1285158 100644
--- a/lib/ray.rb
+++ b/lib/ray.rb
@@ -14,8 +14,11 @@ class Ray
     return Colour.new if depth <= 0
 
     if rec = world.hit(self, Interval.new(0.0001, Float::INFINITY))
-      dir = rec.normal + Vec3.random_unit
-      return Ray.new(rec.point, dir).colour(world, depth - 1) * 0.5
+      if scat = rec.material.scatter(self, rec)
+        return scat.colour(world, depth - 1) * rec.material.attenuation
+      else
+        return Colour.new(0,0,0)
+      end
     end
 
     unit_dir = direction.unit
diff --git a/lib/vec3.rb b/lib/vec3.rb
index 08cbf69..3069b65 100644
--- a/lib/vec3.rb
+++ b/lib/vec3.rb
@@ -56,10 +56,18 @@ class Vec3
     self / mag
   end
 
+  def reflect(normal)
+    self - normal * dot(normal) * 2
+  end
+
   def in_unit_sphere?
     mag_sqr < 1
   end
 
+  def near_zero?(s = 1e-8)
+    @x.abs < s && @y.abs < s && @z.abs < s
+  end
+
   def to_s
     "{#{@x}, #{@y}, #{@z}}"
   end