From 523f9439ed0d2e4c2d51edc623b6c4d62885cfdd Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Wed, 12 Jun 2024 23:19:56 +0100
Subject: Finished chapter 9

---
 lib/hittable.rb |  4 ++--
 lib/ray.rb      |  2 +-
 lib/vec3.rb     | 24 ++++++++++++++++++++----
 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/lib/hittable.rb b/lib/hittable.rb
index 80254d1..c84764f 100644
--- a/lib/hittable.rb
+++ b/lib/hittable.rb
@@ -8,8 +8,8 @@ class HitRecord
   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
+    front_face = ray.direction.dot(out_normal) < 0
+    @normal = front_face ? out_normal : -out_normal
   end
 end
 
diff --git a/lib/ray.rb b/lib/ray.rb
index c1679a5..eb6038c 100644
--- a/lib/ray.rb
+++ b/lib/ray.rb
@@ -14,7 +14,7 @@ class Ray
     return Colour.new if depth <= 0
 
     if rec = world.hit(self, Interval.new(0.0001, Float::INFINITY))
-      dir = Vec3.random_unit(rec.normal)
+      dir = rec.normal + Vec3.random_unit
       return Ray.new(rec.point, dir).colour(world, depth - 1) * 0.5
     end
 
diff --git a/lib/vec3.rb b/lib/vec3.rb
index e24229a..08cbf69 100644
--- a/lib/vec3.rb
+++ b/lib/vec3.rb
@@ -87,12 +87,28 @@ class Colour < Vec3
   def g; @y; end
   def b; @z; end
 
+  def gamma(gma = 2)
+    Colour.new(
+      r > 0 ? r ** (1.0 / gma) : r,
+      g > 0 ? g ** (1.0 / gma) : g,
+      b > 0 ? b ** (1.0 / gma) : b
+    )
+  end
+
+  def clamp(interval)
+    Colour.new(
+      interval.clamp(r),
+      interval.clamp(g),
+      interval.clamp(b)
+    )
+  end
+
   def to_ppm
-    intensity = Interval.new(0.0, 0.999)
+    g_space = gamma.clamp(Interval.new(0.0, 0.999))
     "%3d %3d %3d" % [
-      (intensity.clamp(r) * 256).to_i,
-      (intensity.clamp(g) * 256).to_i,
-      (intensity.clamp(b) * 256).to_i
+      (g_space.r * 256).to_i,
+      (g_space.g * 256).to_i,
+      (g_space.b * 256).to_i
     ]
   end
 end
-- 
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