From 3d377124c1c3b06f4a66e042de01dac4f71cbebe Mon Sep 17 00:00:00 2001
From: Jack Andersen <jackoalan@gmail.com>
Date: Sat, 28 Oct 2017 20:21:23 -1000
Subject: [PATCH] Implement CQuaternion::angleFrom()

---
 include/zeus/CQuaternion.hpp | 2 ++
 src/CQuaternion.cpp          | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/include/zeus/CQuaternion.hpp b/include/zeus/CQuaternion.hpp
index b9b3d19..b539f55 100644
--- a/include/zeus/CQuaternion.hpp
+++ b/include/zeus/CQuaternion.hpp
@@ -274,6 +274,8 @@ public:
     zeus::CVector3f getImaginary() const { return {x, y, z}; }
     void setImaginary(const zeus::CVector3f& i) { x = i.x; y = i.y; z = i.z; }
 
+    CRelAngle angleFrom(const zeus::CQuaternion& other);
+
     inline float& operator[](size_t idx) { return (&w)[idx]; }
     inline const float& operator[](size_t idx) const { return (&w)[idx]; }
 
diff --git a/src/CQuaternion.cpp b/src/CQuaternion.cpp
index c315b92..9297309 100644
--- a/src/CQuaternion.cpp
+++ b/src/CQuaternion.cpp
@@ -271,4 +271,10 @@ CQuaternion CQuaternion::buildEquivalent() const
     else
         return CQuaternion::fromAxisAngle(CUnitVector3f(x, y, z), tmp + 2.0 * M_PI);
 }
+
+CRelAngle CQuaternion::angleFrom(const zeus::CQuaternion& other)
+{
+    return std::acos(zeus::clamp(-1.f, dot(other), 1.f));
+}
+
 }