From c747738b7b9de8f7218156893e82429a25a822a9 Mon Sep 17 00:00:00 2001
From: "Jakob L. Kreuze" <zerodaysfordays@sdf.org>
Date: Mon, 20 Jul 2020 15:23:45 -0400
Subject: Fix `degrees->radians'.

---
 cl-raytracer.lisp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'cl-raytracer.lisp')

diff --git a/cl-raytracer.lisp b/cl-raytracer.lisp
index 23b5232..f30099a 100644
--- a/cl-raytracer.lisp
+++ b/cl-raytracer.lisp
@@ -121,7 +121,7 @@ format (PPM), writing the result to `(current-output-port)'."
 
 (defun to-radians (d)
   "Convert D, a value in degrees, to radians."
-  (* d (/ PI 360)))
+  (* d (/ PI 180)))
 
 
 ;;;
@@ -285,7 +285,7 @@ format (PPM), writing the result to `(current-output-port)'."
 (defun coord-to-ray (x y)
   "Return the ray corresponding to the point X, Y on the viewport plane."
   (let* ((dist 1.0)
-         (top    (* dist (tan (to-radians camera-fov))))
+         (top    (* dist (tan (/ (to-radians camera-fov) 2))))
          (right  (* top image-aspect-ratio))
          (bottom (- top))
          (left   (- right))
-- 
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