From 9768d3a728ebd90e66e9e3b8fd7f99cd577767ce 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: Sat, 25 Sep 2021 19:13:32 -0700
Subject: [PATCH] Added quaternion to axis conversion functions.

---
 include/bx/inline/math.inl | 51 ++++++++++++++++++++++++++++++++++++++
 include/bx/math.h          |  9 +++++++
 2 files changed, 60 insertions(+)

diff --git a/include/bx/inline/math.inl b/include/bx/inline/math.inl
index cbb77a2..6699a73 100644
--- a/include/bx/inline/math.inl
+++ b/include/bx/inline/math.inl
@@ -909,6 +909,57 @@ namespace bx
 		};
 	}
 
+	inline BX_CONST_FUNC Vec3 toXAxis(const Quaternion _a)
+	{
+		const float xx  = _a.x;
+		const float yy  = _a.y;
+		const float zz  = _a.z;
+		const float ww  = _a.w;
+		const float ysq = square(yy);
+		const float zsq = square(zz);
+
+		return
+		{
+			1.0f - 2.0f * ysq     - 2.0f * zsq,
+			       2.0f * xx * yy + 2.0f * zz * ww,
+			       2.0f * xx * zz - 2.0f * yy * ww,
+		};
+	}
+
+	inline BX_CONST_FUNC Vec3 toYAxis(const Quaternion _a)
+	{
+		const float xx  = _a.x;
+		const float yy  = _a.y;
+		const float zz  = _a.z;
+		const float ww  = _a.w;
+		const float xsq = square(xx);
+		const float zsq = square(zz);
+
+		return
+		{
+			       2.0f * xx * yy - 2.0f * zz * ww,
+			1.0f - 2.0f * xsq     - 2.0f * zsq,
+			       2.0f * yy * zz + 2.0f * xx * ww,
+		};
+	}
+
+	inline BX_CONST_FUNC Vec3 toZAxis(const Quaternion _a)
+	{
+		const float xx  = _a.x;
+		const float yy  = _a.y;
+		const float zz  = _a.z;
+		const float ww  = _a.w;
+		const float xsq = square(xx);
+		const float ysq = square(yy);
+
+		return
+		{
+			       2.0f * xx * zz + 2.0f * yy * ww,
+			       2.0f * yy * zz - 2.0f * xx * ww,
+			1.0f - 2.0f * xsq     - 2.0f * ysq,
+		};
+	}
+
 	inline BX_CONST_FUNC Quaternion rotateAxis(const Vec3 _axis, float _angle)
 	{
 		const float ha = _angle * 0.5f;
diff --git a/include/bx/math.h b/include/bx/math.h
index f5f6248..ee4aa29 100644
--- a/include/bx/math.h
+++ b/include/bx/math.h
@@ -492,6 +492,15 @@ namespace bx
 	///
 	BX_CONST_FUNC Vec3 toEuler(const Quaternion _a);
 
+	///
+	BX_CONST_FUNC Vec3 toXAxis(const Quaternion _a);
+
+	///
+	BX_CONST_FUNC Vec3 toYAxis(const Quaternion _a);
+
+	///
+	BX_CONST_FUNC Vec3 toZAxis(const Quaternion _a);
+
 	///
 	BX_CONST_FUNC Quaternion rotateAxis(const Vec3 _axis, float _angle);