From 3549acb5dbd2f6fe43be6cce9828785ccead7e77 Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Fri, 14 Jun 2024 12:23:49 +0100
Subject: Finished! Good god performance nope.

---
 lib/camera.rb | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

(limited to 'lib/camera.rb')

diff --git a/lib/camera.rb b/lib/camera.rb
index 365ebcd..3ddf769 100644
--- a/lib/camera.rb
+++ b/lib/camera.rb
@@ -3,7 +3,8 @@ class Camera
                  aliasing: 10, depth: 10, vfov: 90.0,
                  lookfrom: Point.new(0, 0, 0),
                  lookat: Point.new(0, 0, -1),
-                 vup: Vec3.new(0, 1, 0))
+                 vup: Vec3.new(0, 1, 0),
+                 defocus_angle: 0, focus_dist: 10)
     @width = width
     @aliasing = aliasing
     @depth = depth
@@ -14,13 +15,12 @@ class Camera
 
     # Camera
     @c_centre = lookfrom
-    c_focallength = (lookfrom - lookat).mag
 
     # Viewport
     theta = vfov * Maths::PI / 180
     h = Maths.tan(theta / 2)
-    v_height = 2.0 * h * c_focallength
-    v_width = v_height * @width.to_f / @height
+    v_height = 2.0 * h * focus_dist
+    v_width = (v_height * @width) / @height
 
     # Camera basis vectors
     w = (lookfrom - lookat).unit
@@ -36,8 +36,14 @@ class Camera
 
     # Upper left pixel
     v_upperleft = @c_centre - v_u / 2 - v_v / 2 -
-                  w * c_focallength
+                  w * focus_dist
     @p00_loc = v_upperleft + (@pd_u + @pd_v) / 2
+
+    @defocus_angle = defocus_angle
+    defocus_radius = focus_dist * Maths.tan((@defocus_angle / 2) *
+                                            Maths::PI / 180)
+    @defocus_disk_u = u * defocus_radius
+    @defocus_disk_v = v * defocus_radius
   end
 
   def render(world)
@@ -70,6 +76,13 @@ class Camera
                @pd_u * (col + rand - 0.5) +
                @pd_v * (row + rand - 0.5)
 
-    Ray.new(@c_centre, p_sample - @c_centre)
+    ray_origin = @defocus_angle <= 0 ? @c_centre : defocus_disk_sample
+    ray_dir = p_sample - ray_origin
+    Ray.new(ray_origin, ray_dir)
+  end
+
+  def defocus_disk_sample
+    p = Vec3.random_in_unit(dimensions: 2)
+    @c_centre + @defocus_disk_u * p.x + @defocus_disk_v * p.y
   end
 end
-- 
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