1 files changed, 10 insertions, 0 deletions
diff --git a/lib/ray.rb b/lib/ray.rb
index 4d282cb..47f2b26 100644
--- a/lib/ray.rb
+++ b/lib/ray.rb
@@ -9,4 +9,14 @@ class Ray
   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