Update GLM to latest version (0.9.9.3). This includes GLM's change of matrices no longer default initializing to the identity matrix. This commit thus also includes the update of all of LearnOpenGL's code to reflect this: all matrices are now constructor-initialized to the identity matrix where relevant.

includes/glm/ext/quaternion_common.inl

@@ -0,0 +1,107 @@
+namespace glm
+{
+	template<typename T, qualifier Q>
+	GLM_FUNC_QUALIFIER qua<T, Q> mix(qua<T, Q> const& x, qua<T, Q> const& y, T a)
+	{
+		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'mix' only accept floating-point inputs");
+
+		T const cosTheta = dot(x, y);
+
+		// Perform a linear interpolation when cosTheta is close to 1 to avoid side effect of sin(angle) becoming a zero denominator
+		if(cosTheta > static_cast<T>(1) - epsilon<T>())
+		{
+			// Linear interpolation
+			return qua<T, Q>(
+				mix(x.w, y.w, a),
+				mix(x.x, y.x, a),
+				mix(x.y, y.y, a),
+				mix(x.z, y.z, a));
+		}
+		else
+		{
+			// Essential Mathematics, page 467
+			T angle = acos(cosTheta);
+			return (sin((static_cast<T>(1) - a) * angle) * x + sin(a * angle) * y) / sin(angle);
+		}
+	}
+
+	template<typename T, qualifier Q>
+	GLM_FUNC_QUALIFIER qua<T, Q> lerp(qua<T, Q> const& x, qua<T, Q> const& y, T a)
+	{
+		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'lerp' only accept floating-point inputs");
+
+		// Lerp is only defined in [0, 1]
+		assert(a >= static_cast<T>(0));
+		assert(a <= static_cast<T>(1));
+
+		return x * (static_cast<T>(1) - a) + (y * a);
+	}
+
+	template<typename T, qualifier Q>
+	GLM_FUNC_QUALIFIER qua<T, Q> slerp(qua<T, Q> const& x, qua<T, Q> const& y, T a)
+	{
+		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'slerp' only accept floating-point inputs");
+
+		qua<T, Q> z = y;
+
+		T cosTheta = dot(x, y);
+
+		// If cosTheta < 0, the interpolation will take the long way around the sphere.
+		// To fix this, one quat must be negated.
+		if(cosTheta < static_cast<T>(0))
+		{
+			z = -y;
+			cosTheta = -cosTheta;
+		}
+
+		// Perform a linear interpolation when cosTheta is close to 1 to avoid side effect of sin(angle) becoming a zero denominator
+		if(cosTheta > static_cast<T>(1) - epsilon<T>())
+		{
+			// Linear interpolation
+			return qua<T, Q>(
+				mix(x.w, z.w, a),
+				mix(x.x, z.x, a),
+				mix(x.y, z.y, a),
+				mix(x.z, z.z, a));
+		}
+		else
+		{
+			// Essential Mathematics, page 467
+			T angle = acos(cosTheta);
+			return (sin((static_cast<T>(1) - a) * angle) * x + sin(a * angle) * z) / sin(angle);
+		}
+	}
+
+	template<typename T, qualifier Q>
+	GLM_FUNC_QUALIFIER qua<T, Q> conjugate(qua<T, Q> const& q)
+	{
+		return qua<T, Q>(q.w, -q.x, -q.y, -q.z);
+	}
+
+	template<typename T, qualifier Q>
+	GLM_FUNC_QUALIFIER qua<T, Q> inverse(qua<T, Q> const& q)
+	{
+		return conjugate(q) / dot(q, q);
+	}
+
+	template<typename T, qualifier Q>
+	GLM_FUNC_QUALIFIER vec<4, bool, Q> isnan(qua<T, Q> const& q)
+	{
+		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'isnan' only accept floating-point inputs");
+
+		return vec<4, bool, Q>(isnan(q.x), isnan(q.y), isnan(q.z), isnan(q.w));
+	}
+
+	template<typename T, qualifier Q>
+	GLM_FUNC_QUALIFIER vec<4, bool, Q> isinf(qua<T, Q> const& q)
+	{
+		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'isinf' only accept floating-point inputs");
+
+		return vec<4, bool, Q>(isinf(q.x), isinf(q.y), isinf(q.z), isinf(q.w));
+	}
+}//namespace glm
+
+#if GLM_CONFIG_SIMD == GLM_ENABLE
+#	include "quaternion_common_simd.inl"
+#endif
+