From 279b8ff3c0a5b86a91451dc618d6da59444da517 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=91=D1=80=D0=B0=D0=BD=D0=B8=D0=BC=D0=B8=D1=80=20=D0=9A?=
 =?UTF-8?q?=D0=B0=D1=80=D0=B0=D1=9F=D0=B8=D1=9B?=
 <branimirkaradzic@gmail.com>
Date: Sun, 20 Dec 2020 11:06:55 -0800
Subject: [PATCH] Added invSmoothStep.

---
 include/bx/inline/math.inl | 5 +++++
 include/bx/math.h          | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/include/bx/inline/math.inl b/include/bx/inline/math.inl
index 9afacc0..aba2eee 100644
--- a/include/bx/inline/math.inl
+++ b/include/bx/inline/math.inl
@@ -344,6 +344,11 @@ namespace bx
 		return square(_a)*(3.0f - 2.0f*_a);
 	}
 
+	inline BX_CONST_FUNC float invSmoothStep(float _a)
+	{
+		return 0.5f - sin(asin(1.0f - 2.0f * _a) / 3.0f);
+	}
+
 	inline BX_CONSTEXPR_FUNC float bias(float _time, float _bias)
 	{
 		return _time / ( ( (1.0f/_bias - 2.0f)*(1.0f - _time) ) + 1.0f);
diff --git a/include/bx/math.h b/include/bx/math.h
index 4e39ad3..e51bdd2 100644
--- a/include/bx/math.h
+++ b/include/bx/math.h
@@ -282,6 +282,9 @@ namespace bx
 	///
 	BX_CONSTEXPR_FUNC float smoothStep(float _a);
 
+	///
+	BX_CONST_FUNC float invSmoothStep(float _a);
+
 	///
 	BX_CONSTEXPR_FUNC float bias(float _time, float _bias);