Matrix3x3: support multiplication of vectors of different type.

[x] TODO: correct operator order in decltype(), include the addition too

libs_required/ACG/Math/Matrix3x3T.hh

@@ -128,20 +128,26 @@ class Matrix3x3T {
             }};
         }
 
-        constexpr Vec3 operator*(const Vec3 &rhs) const {
-            return Vec3(
+        template<typename OtherScalar>
+        constexpr auto operator*(const VectorT<OtherScalar,3> &rhs) const
+        -> OpenMesh::VectorT<decltype((*this)(0,0) * rhs[0]), 3>
+        {
+            return {
                 (*this)(0, 0) * rhs[0] + (*this)(0, 1) * rhs[1] + (*this)(0, 2) * rhs[2],
                 (*this)(1, 0) * rhs[0] + (*this)(1, 1) * rhs[1] + (*this)(1, 2) * rhs[2],
                 (*this)(2, 0) * rhs[0] + (*this)(2, 1) * rhs[1] + (*this)(2, 2) * rhs[2]
-            );
+            };
         }
 
-        constexpr friend Vec3 operator*(Vec3 v, const Matrix3x3T &rhs) {
-            return Vec3(
+        template<typename OtherScalar>
+        constexpr friend auto operator*(VectorT<OtherScalar,3> v, const Matrix3x3T &rhs)
+        -> OpenMesh::VectorT<decltype(rhs(0,0) * v[0]), 3>
+        {
+            return {
                 rhs(0, 0) * v[0] + rhs(0, 1) * v[1] + rhs(0, 2) * v[2],
                 rhs(1, 0) * v[0] + rhs(1, 1) * v[1] + rhs(1, 2) * v[2],
                 rhs(2, 0) * v[0] + rhs(2, 1) * v[1] + rhs(2, 2) * v[2]
-            );
+            };
         }
 
         constexpr Matrix3x3T operator*(Scalar c) const {