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'.

---
 gerbil-raytracer.ss | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'gerbil-raytracer.ss')

diff --git a/gerbil-raytracer.ss b/gerbil-raytracer.ss
index 9251bd4..188da7a 100644
--- a/gerbil-raytracer.ss
+++ b/gerbil-raytracer.ss
@@ -137,12 +137,12 @@
 ;; Convert D, a value in degrees, to radians.
 (def (degrees->radians d)
   (let ((pi 3.1415926535897932384626433))
-    (* d (/ pi 360))))
+    (* d (/ pi 180))))
 
 ;; Return the ray corresponding to the point X, Y on the viewport plane.
 (def (coordinate->ray x y)
   (let* ((dist 1.0)
-         (top    (* dist (tan (degrees->radians camera-fov))))
+         (top    (* dist (tan (/ (degrees->radians camera-fov) 2))))
          (right  (* top image-aspect-ratio))
          (bottom (- top))
          (left   (- right))
-- 
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