From 4256034f7f96f2fe3357590f070257299e7dd731 Mon Sep 17 00:00:00 2001
From: Zak Strange <zak@strangedev.net>
Date: Thu, 24 Mar 2016 15:39:50 -0700
Subject: [PATCH] Changed Perspective again

---
 HandmadeMath.h | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/HandmadeMath.h b/HandmadeMath.h
index 9de3261..370be31 100644
--- a/HandmadeMath.h
+++ b/HandmadeMath.h
@@ -711,18 +711,13 @@ Orthographic(float Left, float Right, float Bottom, float Top, float Near, float
 HMMDEF mat4
 Perspective(float FOV, float AspectRatio, float Near, float Far)
 {
-    double Radians = FOV / 2 * HMM_PI / 180;
-    double Sine = sin(Radians);
-    double Cotangent = cos(Radians) / Sine;
-
-    double DeltaZ = Far - Near;        
-
     mat4 Result = Mat4d(1.0f);
-    Result.Elements[0][0] = (float)Cotangent / AspectRatio;
-    Result.Elements[1][1] = (float)Cotangent;
-    Result.Elements[2][2] = (float)(-(Far + Near) / DeltaZ);
-    Result.Elements[2][3] = (float)-1;
-    Result.Elements[3][2] = (float)(-2 * Near * Far / DeltaZ);
+
+    Result.Elements[0][0] = 1.0f / (AspectRatio  * tan(FOV / 2.0f));
+    Result.Elements[1][1] = 1.0f / tan(FOV / 2.0f);
+    Result.Elements[2][3] = -1.0f;
+    Result.Elements[2][2] = -(Far + Near) / (Far - Near);
+    Result.Elements[3][2] = -(2.0f * Far * Near) / (Far - Near);
     Result.Elements[3][3] = 0;
 
     return(Result);