From 3bf56da7aa64ea3ca05559a4e52df8f596bcf86b Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Thu, 13 Jun 2024 18:15:56 +0100
Subject: Finish Chapter 12

---
 lib/camera.rb | 31 +++++++++++++++++++++----------
 rtiaw         |  6 +++++-
 2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/lib/camera.rb b/lib/camera.rb
index 6a3b190..365ebcd 100644
--- a/lib/camera.rb
+++ b/lib/camera.rb
@@ -1,23 +1,34 @@
 class Camera
-  def initialize(width = 100, aspect = 1.0, aliasing = 10, depth = 10)
+  def initialize(width = 100, aspect = 1.0,
+                 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))
     @width = width
-    @aspect = aspect
     @aliasing = aliasing
     @depth = depth
 
     # Height
-    @height = (@width / @aspect).to_i
+    @height = (@width / aspect).to_i
     @height = @height < 1 ? 1 : @height
 
     # Camera
-    c_focallength = 1.0
-    @c_centre = Point.new(0,0,0)
+    @c_centre = lookfrom
+    c_focallength = (lookfrom - lookat).mag
 
     # Viewport
-    @v_height = 2.0
-    @v_width = @v_height * @width.to_f / @height
-    v_u = Vec3.new(@v_width, 0, 0)
-    v_v = Vec3.new(0, -@v_height, 0)
+    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
+
+    # Camera basis vectors
+    w = (lookfrom - lookat).unit
+    u = vup.cross(w).unit
+    v = w.cross(u)
+
+    v_u = u * v_width
+    v_v = -v * v_height
 
     # Pixel deltas
     @pd_u = v_u / @width
@@ -25,7 +36,7 @@ class Camera
 
     # Upper left pixel
     v_upperleft = @c_centre - v_u / 2 - v_v / 2 -
-                  Vec3.new(0, 0, c_focallength)
+                  w * c_focallength
     @p00_loc = v_upperleft + (@pd_u + @pd_v) / 2
   end
 
diff --git a/rtiaw b/rtiaw
index 45487b9..234aa85 100755
--- a/rtiaw
+++ b/rtiaw
@@ -1,5 +1,7 @@
 #!/usr/bin/env ruby
 
+Maths = Math
+
 $LOAD_PATH.unshift(File.join(File.dirname(__FILE__), 'lib'))
 require 'interval'
 require 'vec3'
@@ -21,5 +23,7 @@ world << Sphere.new(-1,      0,   -1,    0.5,    mat_left)
 world << Sphere.new(-1,      0,   -1,    0.4,    mat_bubble)
 world << Sphere.new( 1,      0,   -1,    0.5,    mat_right)
 
-camera = Camera.new(400, 16.0 / 9)
+camera = Camera.new(400, 16.0 / 9,
+                    vfov: 20,
+                    lookfrom: Point.new(-2,2,1))
 camera.render(world)
-- 
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