From e2cf0d6041e3612f9ae1092ab87d4698655f1dd9 Mon Sep 17 00:00:00 2001
From: hyzboy <hyzboy@gmail.com>
Date: Mon, 20 Jan 2020 16:57:33 +0800
Subject: [PATCH] add ApproxPow22

---
 inc/hgl/math/FastTriangle.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/inc/hgl/math/FastTriangle.h b/inc/hgl/math/FastTriangle.h
index 3c4d68d..2f626c0 100644
--- a/inc/hgl/math/FastTriangle.h
+++ b/inc/hgl/math/FastTriangle.h
@@ -19,5 +19,15 @@ namespace hgl
     }
 
     double Latan2(double y, double x);                          ///<低精度atan2函数
+
+    /**
+     * 近似Pow2.2，使用此函数等于pow(x,2.2)
+     * The MIT License
+     * Copyright © 2019 Inigo Quilez
+     */
+    double inline ApproxPow22(double x)
+    {
+        return ((exp2(x)-1.0)-x*0.693147)*3.258891;
+    }
 }//namespace hgl
 #endif//HGL_ALGORITHM_MATH_FAST_TRIANGLE_FUNCTION_INCLUDE