diff --git a/libs/geom/include/psemek/geom/quaternion.hpp b/libs/geom/include/psemek/geom/quaternion.hpp
index 67d601d8..a7a378fa 100644
--- a/libs/geom/include/psemek/geom/quaternion.hpp
+++ b/libs/geom/include/psemek/geom/quaternion.hpp
@@ -199,6 +199,17 @@ namespace psemek::geom
 		}
 	}
 
+	template <typename T>
+	quaternion<T> exp(quaternion<T> const & q)
+	{
+		auto v = vector{q[0], q[1], q[2]};
+		auto l = length(v);
+
+		auto s = sin_over_x(l);
+
+		return std::exp(q[3]) * quaternion<T>({v[0] * s, v[1] * s, v[2] * s, std::cos(l)});
+	}
+
 	template <typename T>
 	std::ostream & operator << (std::ostream & os, quaternion<T> const & q)
 	{