diff --git a/libs/geom/include/psemek/geom/quaternion.hpp b/libs/geom/include/psemek/geom/quaternion.hpp
index da1de6d3..497178de 100644
--- a/libs/geom/include/psemek/geom/quaternion.hpp
+++ b/libs/geom/include/psemek/geom/quaternion.hpp
@@ -165,6 +165,12 @@ namespace psemek::geom
 		return {res[0], res[1], res[2]};
 	}
 
+	template <typename T>
+	T angle(quaternion<T> const & q0, quaternion<T> const & q1)
+	{
+		return std::acos(std::min(T{1}, std::abs(dot(q0.coords, q1.coords))));
+	}
+
 	template <typename T>
 	quaternion<T> slerp(quaternion<T> const & q0, quaternion<T> const & q1, T const & t)
 	{
@@ -191,5 +197,4 @@ namespace psemek::geom
 		}
 	}
 
-
 }