diff --git a/src/adaptors/rotmat.rs b/src/adaptors/rotmat.rs
index 8e253eb6..4a00766a 100644
--- a/src/adaptors/rotmat.rs
+++ b/src/adaptors/rotmat.rs
@@ -5,15 +5,18 @@ use traits::rlmul::{RMul, LMul};
 use traits::cross::Cross;
 use traits::dim::Dim;
 use traits::inv::Inv;
+use traits::row::Row;
+use traits::col::Col;
 use traits::transpose::Transpose;
-use traits::rotation::{Rotation, Rotate};
+use traits::absolute::Absolute;
+use traits::rotation::{Rotation, Rotate, RotationMatrix};
 use traits::transformation::{Transform}; // FIXME: implement Transformation and Transformable
 use traits::homogeneous::ToHomogeneous;
 use traits::indexable::Indexable;
 use traits::norm::Norm;
-use vec::Vec1;
+use traits::comp::absolute_rotate::AbsoluteRotate;
+use vec::{Vec1, Vec2, Vec3};
 use mat::{Mat2, Mat3};
-use vec::Vec3;
 
 /// Matrix wrapper representing rotation matrix. It is built uppon another matrix and ensures (at
 /// the type-level) that it will always represent a rotation. Rotation matrices have some
@@ -120,6 +123,14 @@ impl<N: Clone + Num + Algebraic> Rotmat<Mat3<N>> {
     }
 }
 
+impl<N: Trigonometric + Num + Clone>
+RotationMatrix<Vec2<N>, Vec1<N>, Rotmat<Mat2<N>>> for Rotmat<Mat2<N>> {
+    #[inline]
+    fn to_rot_mat(&self) -> Rotmat<Mat2<N>> {
+        self.clone()
+    }
+}
+
 impl<N: Trigonometric + Num + Clone>
 Rotation<Vec1<N>> for Rotmat<Mat2<N>> {
     #[inline]
@@ -148,6 +159,14 @@ Rotation<Vec1<N>> for Rotmat<Mat2<N>> {
     }
 }
 
+impl<N: NumCast + Algebraic + Trigonometric + Num + Clone>
+RotationMatrix<Vec3<N>, Vec3<N>, Rotmat<Mat3<N>>> for Rotmat<Mat3<N>> {
+    #[inline]
+    fn to_rot_mat(&self) -> Rotmat<Mat3<N>> {
+        self.clone()
+    }
+}
+
 impl<N: Clone + Trigonometric + Num + Algebraic + NumCast>
 Rotation<Vec3<N>> for Rotmat<Mat3<N>> {
     #[inline]
@@ -304,8 +323,42 @@ Transpose for Rotmat<M> {
     }
 }
 
+impl<M: Row<R>, R> Row<R> for Rotmat<M> {
+    #[inline]
+    fn num_rows(&self) -> uint {
+        self.submat.num_rows()
+    }
+    #[inline]
+    fn row(&self, i: uint) -> R {
+        self.submat.row(i)
+    }
+
+    #[inline]
+    fn set_row(&mut self, i: uint, row: R) {
+        self.submat.set_row(i, row);
+    }
+}
+
+impl<M: Col<C>, C> Col<C> for Rotmat<M> {
+    #[inline]
+    fn num_cols(&self) -> uint {
+        self.submat.num_cols()
+    }
+
+    #[inline]
+    fn col(&self, i: uint) -> C {
+        self.submat.col(i)
+    }
+
+    #[inline]
+    fn set_col(&mut self, i: uint, col: C) {
+        self.submat.set_col(i, col);
+    }
+}
+
 // we loose the info that we are a rotation matrix
 impl<M: ToHomogeneous<M2>, M2> ToHomogeneous<M2> for Rotmat<M> {
+    #[inline]
     fn to_homogeneous(&self) -> M2 {
         self.submat.to_homogeneous()
     }
@@ -328,3 +381,33 @@ impl<N: ApproxEq<N>, M: ApproxEq<N>> ApproxEq<N> for Rotmat<M> {
         self.submat.approx_eq_eps(&other.submat, epsilon)
     }
 }
+
+impl<M: Absolute<M2>, M2> Absolute<M2> for Rotmat<M> {
+    #[inline]
+    fn absolute(&self) -> M2 {
+        self.submat.absolute()
+    }
+}
+
+impl<N: Signed> AbsoluteRotate<Vec3<N>> for Rotmat<Mat3<N>> {
+    #[inline]
+    fn absolute_rotate(&self, v: &Vec3<N>) -> Vec3<N> {
+        Vec3::new(
+            self.submat.m11.abs() * v.x + self.submat.m12.abs() * v.y + self.submat.m13.abs() * v.z,
+            self.submat.m21.abs() * v.x + self.submat.m22.abs() * v.y + self.submat.m23.abs() * v.z,
+            self.submat.m31.abs() * v.x + self.submat.m32.abs() * v.y + self.submat.m33.abs() * v.z)
+    }
+}
+
+impl<N: Signed> AbsoluteRotate<Vec2<N>> for Rotmat<Mat2<N>> {
+    #[inline]
+    fn absolute_rotate(&self, v: &Vec2<N>) -> Vec2<N> {
+        // the matrix is skew-symetric, so we dont need to compute the absolute value of every
+        // component.
+        let m11 = self.submat.m11.abs();
+        let m12 = self.submat.m12.abs();
+        let m22 = self.submat.m22.abs();
+
+        Vec2::new(m11 * v.x + m12 * v.y, m12 * v.x + m22 * v.y)
+    }
+}
diff --git a/src/adaptors/transform.rs b/src/adaptors/transform.rs
index 04e22161..ec31f7ef 100644
--- a/src/adaptors/transform.rs
+++ b/src/adaptors/transform.rs
@@ -2,14 +2,17 @@ use std::num::{One, Zero};
 use std::rand::{Rand, Rng, RngUtil};
 use std::cmp::ApproxEq;
 use traits::dim::Dim;
+use traits::absolute::Absolute;
+use traits::mat::Mat;
 use traits::inv::Inv;
-use traits::rotation::{Rotation, Rotate};
+use traits::rotation::{Rotation, Rotate, RotationMatrix};
 use traits::translation::{Translation, Translate};
 use Ts = traits::transformation::Transform;
 use traits::transformation::{Transformation};
 use traits::rlmul::{RMul, LMul};
 use traits::homogeneous::{ToHomogeneous, FromHomogeneous};
 use traits::column::Column;
+use traits::comp::absolute_rotate::AbsoluteRotate;
 use adaptors::rotmat::Rotmat;
 use vec::Vec3;
 use mat::Mat3;
@@ -53,6 +56,14 @@ impl<V: Clone, M: Clone> Transform<V, M> {
     }
 }
 
+impl<LV, AV, M: One + RMul<LV> + RotationMatrix<LV, AV, M2>, M2: Mat<LV, LV> + Rotation<AV>>
+RotationMatrix<LV, AV, M2> for Transform<LV, M> {
+    #[inline]
+    fn to_rot_mat(&self) -> M2 {
+        self.submat.to_rot_mat()
+    }
+}
+
 impl<N: Clone + Num + Algebraic> Transform<Vec3<N>, Rotmat<Mat3<N>>> {
     /// Reorient and translate this transformation such that its local `x` axis points to a given
     /// direction.  Note that the usually known `look_at` function does the same thing but with the
@@ -342,3 +353,18 @@ impl<M: Rand, V: Rand> Rand for Transform<V, M> {
         Transform::new(rng.gen(), rng.gen())
     }
 }
+
+impl<V: Absolute<V2>, M: Absolute<M2>, V2, M2>
+Absolute<Transform<V2, M2>> for Transform<V, M> {
+    #[inline]
+    fn absolute(&self) -> Transform<V2, M2> {
+        Transform::new(self.subtrans.absolute(), self.submat.absolute())
+    }
+}
+
+impl<V, M: AbsoluteRotate<V>> AbsoluteRotate<V> for Transform<V, M> {
+    #[inline]
+    fn absolute_rotate(&self, v: &V) -> V {
+        self.submat.absolute_rotate(v)
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 00cb94ec..970dec47 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -29,16 +29,14 @@ mod vec0_spec;
 mod identity_spec;
 
 /// Wrappers around raw matrices to restrict their behaviour.
-pub mod adaptors
-{
+pub mod adaptors {
     pub mod rotmat;
     pub mod transform;
 }
 
 pub mod types;
 
-pub mod traits
-{
+pub mod traits {
     pub mod vector;
     pub mod sample;
     pub mod indexable;
@@ -61,11 +59,21 @@ pub mod traits
     pub mod mat_cast;
     pub mod norm;
     pub mod dot;
+    pub mod mat;
+    pub mod absolute;
+    pub mod col;
+
+    /// Unusual traits which are composition of other primitive traits.
+    /// Those are mainly shortcuts to make some operation easier to use or faster.
+    /// Mathematics purists should really not go in there!
+    pub mod comp {
+        pub mod rotation_with_translation;
+        pub mod absolute_rotate;
+    }
 }
 
 #[cfg(test)]
-pub mod tests
-{
+pub mod tests {
     pub mod mat;
     pub mod vec;
 }
diff --git a/src/mat.rs b/src/mat.rs
index ed116313..fd1f233e 100644
--- a/src/mat.rs
+++ b/src/mat.rs
@@ -7,6 +7,8 @@ use std::vec::{VecIterator, VecMutIterator};
 use vec::{Vec1, Vec2, Vec3, Vec4, Vec5, Vec6, Outer};
 
 // traits
+pub use traits::mat::Mat;
+pub use traits::absolute::Absolute;
 pub use traits::dim::Dim;
 pub use traits::indexable::Indexable;
 pub use traits::iterable::{Iterable, IterableMut};
@@ -15,12 +17,15 @@ pub use traits::mat_cast::MatCast;
 pub use traits::column::Column;
 pub use traits::inv::Inv;
 pub use traits::rlmul::{RMul, LMul};
-pub use traits::rotation::{Rotation, Rotate, RotationWithTranslation};
+pub use traits::rotation::{Rotation, RotationMatrix, Rotate};
 pub use traits::transformation::{Transformation, Transform};
 pub use traits::translation::{Translation, Translate};
 pub use traits::transpose::{Transpose};
 pub use traits::homogeneous::{ToHomogeneous, FromHomogeneous};
 pub use traits::row::Row;
+pub use traits::col::Col;
+pub use traits::comp::rotation_with_translation::RotationWithTranslation;
+pub use traits::comp::absolute_rotate::AbsoluteRotate;
 
 // structs
 pub use dmat::DMat;
@@ -57,6 +62,7 @@ scalar_mul_impl!(Mat1, m11)
 scalar_div_impl!(Mat1, m11)
 scalar_add_impl!(Mat1, m11)
 scalar_sub_impl!(Mat1, m11)
+absolute_impl!(Mat1, m11)
 one_impl!(Mat1, One::one)
 iterable_impl!(Mat1, 1)
 iterable_mut_impl!(Mat1, 1)
@@ -71,6 +77,7 @@ transpose_impl!(Mat1, 1)
 approx_eq_impl!(Mat1)
 column_impl!(Mat1, Vec1, 1)
 row_impl!(Mat1, Vec1, 1)
+col_impl!(Mat1, Vec1, 1)
 to_homogeneous_impl!(Mat1, Mat2, 1, 2)
 from_homogeneous_impl!(Mat1, Mat2, 1, 2)
 outer_impl!(Vec1, Mat1)
@@ -98,6 +105,8 @@ scalar_add_impl!(Mat2, m11, m12,
                        m21, m22)
 scalar_sub_impl!(Mat2, m11, m12,
                        m21, m22)
+absolute_impl!(Mat2, m11, m12,
+                     m21, m22)
 one_impl!(Mat2, One::one,   Zero::zero,
                 Zero::zero, One::one)
 iterable_impl!(Mat2, 2)
@@ -113,6 +122,7 @@ transpose_impl!(Mat2, 2)
 approx_eq_impl!(Mat2)
 column_impl!(Mat2, Vec2, 2)
 row_impl!(Mat2, Vec2, 2)
+col_impl!(Mat2, Vec2, 2)
 to_homogeneous_impl!(Mat2, Mat3, 2, 3)
 from_homogeneous_impl!(Mat2, Mat3, 2, 3)
 outer_impl!(Vec2, Mat2)
@@ -149,6 +159,9 @@ scalar_add_impl!(Mat3, m11, m12, m13,
 scalar_sub_impl!(Mat3, m11, m12, m13,
                        m21, m22, m23,
                        m31, m32, m33)
+absolute_impl!(Mat3, m11, m12, m13,
+                     m21, m22, m23,
+                     m31, m32, m33)
 one_impl!(Mat3, One::one  , Zero::zero, Zero::zero,
                 Zero::zero, One::one  , Zero::zero,
                 Zero::zero, Zero::zero, One::one)
@@ -165,6 +178,7 @@ transpose_impl!(Mat3, 3)
 approx_eq_impl!(Mat3)
 column_impl!(Mat3, Vec3, 3)
 // (specialized) row_impl!(Mat3, Vec3, 3)
+// (specialized) col_impl!(Mat3, Vec3, 3)
 to_homogeneous_impl!(Mat3, Mat4, 3, 4)
 from_homogeneous_impl!(Mat3, Mat4, 3, 4)
 outer_impl!(Vec3, Mat3)
@@ -226,6 +240,12 @@ scalar_sub_impl!(Mat4,
   m31, m32, m33, m34,
   m41, m42, m43, m44
 )
+absolute_impl!(Mat4,
+  m11, m12, m13, m14,
+  m21, m22, m23, m24,
+  m31, m32, m33, m34,
+  m41, m42, m43, m44
+)
 one_impl!(Mat4, One::one  , Zero::zero, Zero::zero, Zero::zero,
                 Zero::zero, One::one  , Zero::zero, Zero::zero,
                 Zero::zero, Zero::zero, One::one  , Zero::zero,
@@ -243,6 +263,7 @@ transpose_impl!(Mat4, 4)
 approx_eq_impl!(Mat4)
 column_impl!(Mat4, Vec4, 4)
 row_impl!(Mat4, Vec4, 4)
+col_impl!(Mat4, Vec4, 4)
 to_homogeneous_impl!(Mat4, Mat5, 4, 5)
 from_homogeneous_impl!(Mat4, Mat5, 4, 5)
 outer_impl!(Vec4, Mat4)
@@ -271,6 +292,13 @@ mat_cast_impl!(Mat5,
   m41, m42, m43, m44, m45,
   m51, m52, m53, m54, m55
 )
+absolute_impl!(Mat5,
+  m11, m12, m13, m14, m15,
+  m21, m22, m23, m24, m25,
+  m31, m32, m33, m34, m35,
+  m41, m42, m43, m44, m45,
+  m51, m52, m53, m54, m55
+)
 one_impl!(Mat5,
   One::one  , Zero::zero, Zero::zero, Zero::zero, Zero::zero,
   Zero::zero, One::one  , Zero::zero, Zero::zero, Zero::zero,
@@ -333,6 +361,7 @@ transpose_impl!(Mat5, 5)
 approx_eq_impl!(Mat5)
 column_impl!(Mat5, Vec5, 5)
 row_impl!(Mat5, Vec5, 5)
+col_impl!(Mat5, Vec5, 5)
 to_homogeneous_impl!(Mat5, Mat6, 5, 6)
 from_homogeneous_impl!(Mat5, Mat6, 5, 6)
 outer_impl!(Vec5, Mat5)
@@ -412,6 +441,14 @@ scalar_sub_impl!(Mat6,
   m51, m52, m53, m54, m55, m56,
   m61, m62, m63, m64, m65, m66
 )
+absolute_impl!(Mat6,
+  m11, m12, m13, m14, m15, m16,
+  m21, m22, m23, m24, m25, m26,
+  m31, m32, m33, m34, m35, m36,
+  m41, m42, m43, m44, m45, m46,
+  m51, m52, m53, m54, m55, m56,
+  m61, m62, m63, m64, m65, m66
+)
 one_impl!(Mat6,
   One::one  , Zero::zero, Zero::zero, Zero::zero, Zero::zero, Zero::zero,
   Zero::zero, One::one  , Zero::zero, Zero::zero, Zero::zero, Zero::zero,
@@ -433,4 +470,5 @@ transpose_impl!(Mat6, 6)
 approx_eq_impl!(Mat6)
 column_impl!(Mat6, Vec6, 6)
 row_impl!(Mat6, Vec6, 6)
+col_impl!(Mat6, Vec6, 6)
 outer_impl!(Vec6, Mat6)
diff --git a/src/mat_macros.rs b/src/mat_macros.rs
index 60753a00..aaa22fb4 100644
--- a/src/mat_macros.rs
+++ b/src/mat_macros.rs
@@ -105,6 +105,17 @@ macro_rules! scalar_sub_impl(
   )
 )
 
+macro_rules! absolute_impl(
+  ($t: ident, $comp0: ident $(,$compN: ident)*) => (
+    impl<N: Signed> Absolute<$t<N>> for $t<N> {
+        #[inline]
+        fn absolute(&self) -> $t<N> {
+            $t::new(self.$comp0.abs() $(, self.$compN.abs() )*)
+        }
+    }
+  )
+)
+
 macro_rules! iterable_impl(
   ($t: ident, $dim: expr) => (
     impl<N> Iterable<N> for $t<N> {
@@ -208,6 +219,11 @@ macro_rules! column_impl(
 macro_rules! row_impl(
   ($t: ident, $tv: ident, $dim: expr) => (
     impl<N: Clone + Zero> Row<$tv<N>> for $t<N> {
+        #[inline]
+        fn num_rows(&self) -> uint {
+            Dim::dim(None::<$t<N>>)
+        }
+
         #[inline]
         fn set_row(&mut self, row: uint, v: $tv<N>) {
             for (i, e) in v.iter().enumerate() {
@@ -229,6 +245,35 @@ macro_rules! row_impl(
   )
 )
 
+macro_rules! col_impl(
+  ($t: ident, $tv: ident, $dim: expr) => (
+    impl<N: Clone + Zero> Col<$tv<N>> for $t<N> {
+        #[inline]
+        fn num_cols(&self) -> uint {
+            Dim::dim(None::<$t<N>>)
+        }
+
+        #[inline]
+        fn set_col(&mut self, col: uint, v: $tv<N>) {
+            for (i, e) in v.iter().enumerate() {
+                self.set((col, i), e.clone());
+            }
+        }
+
+        #[inline]
+        fn col(&self, col: uint) -> $tv<N> {
+            let mut res: $tv<N> = Zero::zero();
+
+            for (i, e) in res.mut_iter().enumerate() {
+                *e = self.at((i, col));
+            }
+
+            res
+        }
+    }
+  )
+)
+
 macro_rules! mul_impl(
   ($t: ident, $dim: expr) => (
     impl<N: Clone + Num> Mul<$t<N>, $t<N>> for $t<N> {
diff --git a/src/mat_spec.rs b/src/mat_spec.rs
index 75d6e57a..4de3f8cb 100644
--- a/src/mat_spec.rs
+++ b/src/mat_spec.rs
@@ -1,6 +1,6 @@
 use std::num::{Zero, One};
 use vec::Vec3;
-use mat::{Mat1, Mat2, Mat3, Inv, Row};
+use mat::{Mat1, Mat2, Mat3, Inv, Row, Col};
 use mat;
 
 // some specializations:
@@ -110,6 +110,11 @@ Inv for Mat3<N> {
 }
 
 impl<N: Clone> Row<Vec3<N>> for Mat3<N> {
+    #[inline]
+    fn num_rows(&self) -> uint {
+        3
+    }
+
     #[inline]
     fn row(&self, i: uint) -> Vec3<N> {
         match i {
@@ -144,6 +149,46 @@ impl<N: Clone> Row<Vec3<N>> for Mat3<N> {
     }
 }
 
+impl<N: Clone> Col<Vec3<N>> for Mat3<N> {
+    #[inline]
+    fn num_cols(&self) -> uint {
+        3
+    }
+
+    #[inline]
+    fn col(&self, i: uint) -> Vec3<N> {
+        match i {
+            0 => Vec3::new(self.m11.clone(), self.m21.clone(), self.m31.clone()),
+            1 => Vec3::new(self.m12.clone(), self.m22.clone(), self.m32.clone()),
+            2 => Vec3::new(self.m13.clone(), self.m23.clone(), self.m33.clone()),
+            _ => fail!("Index out of range: 3d matrices do not have " + i.to_str() + " cols.")
+        }
+    }
+
+    #[inline]
+    fn set_col(&mut self, i: uint, r: Vec3<N>) {
+        match i {
+            0 => {
+                self.m11 = r.x.clone();
+                self.m21 = r.y.clone();
+                self.m31 = r.z;
+            },
+            1 => {
+                self.m12 = r.x.clone();
+                self.m22 = r.y.clone();
+                self.m32 = r.z;
+            },
+            2 => {
+                self.m13 = r.x.clone();
+                self.m23 = r.y.clone();
+                self.m33 = r.z;
+            },
+            _ => fail!("Index out of range: 3d matrices do not have " + i.to_str() + " cols.")
+
+        }
+    }
+}
+
 // FIXME: move this to another file?
 impl<N: Real + NumCast + Zero + One> mat::Mat4<N> {
     /// Computes a projection matrix given the frustrum near plane width, height, the field of
diff --git a/src/traits/absolute.rs b/src/traits/absolute.rs
new file mode 100644
index 00000000..8d57c11e
--- /dev/null
+++ b/src/traits/absolute.rs
@@ -0,0 +1,7 @@
+/// Trait of objects having an absolute value.
+/// This is useful of the object and the absolute value do not have the same type.
+pub trait Absolute<A> {
+    /// Compute some absolute representation of this object.
+    /// Typically, this will make all component of a matrix or vector positive.
+    fn absolute(&self) -> A;
+}
diff --git a/src/traits/col.rs b/src/traits/col.rs
new file mode 100644
index 00000000..b604fde7
--- /dev/null
+++ b/src/traits/col.rs
@@ -0,0 +1,9 @@
+/// Traits to access columns of a matrix or vector.
+pub trait Col<C> {
+    /// The number of columun of this matrix or vector.
+    fn num_cols(&self) -> uint;
+    /// Reads the `i`-th column of `self`.
+    fn col(&self, i: uint) -> C;
+    /// Writes the `i`-th column of `self`.
+    fn set_col(&mut self, i: uint, C);
+}
diff --git a/src/traits/comp/absolute_rotate.rs b/src/traits/comp/absolute_rotate.rs
new file mode 100644
index 00000000..f0532dc3
--- /dev/null
+++ b/src/traits/comp/absolute_rotate.rs
@@ -0,0 +1,16 @@
+/// Trait of matrices having the following operation:
+///
+///     self.absolute_rotate(v) = self.rotation_matrix().absolute().rmul(v)
+///
+/// The operation is accessible using the `RotationMatrix`, `Absolute`, and `RMul` traits, but
+/// doing so is not easy in generic code as it can be a cause of type over-parametrization.
+///
+/// # Known use case:
+///     * to compute efficiently the AABB of a rotated AABB.
+pub trait AbsoluteRotate<V> {
+
+    /// This is the same as:
+    ///
+    ///     self.absolute_rotate(v) = self.rotation_matrix().absolute().rmul(v)
+    fn absolute_rotate(&self, &V) -> V;
+}
diff --git a/src/traits/comp/rotation_with_translation.rs b/src/traits/comp/rotation_with_translation.rs
new file mode 100644
index 00000000..b196177b
--- /dev/null
+++ b/src/traits/comp/rotation_with_translation.rs
@@ -0,0 +1,70 @@
+use traits::rotation::Rotation;
+use traits::translation::Translation;
+
+// NOTE: we cannot call this an Isometry since an isometry really does not need to have a rotation
+// nor a translation (this can be a reflexion).
+/// Utilities to make rotations with regard to a point different than the origin.
+/// All those operations are the composition of rotations and translations.
+/// This could be implemented in term of the `Rotation` and `Translation` traits, but having those
+/// here make it easier to use.
+///
+/// # Known use case:
+///     * to change the center of a rotation.
+pub trait RotationWithTranslation<LV: Neg<LV>, AV>: Rotation<AV> + Translation<LV> {
+    /**
+     * Applies a rotation centered on a specific point.
+     *
+     *   - `m`:       the object to be rotated.
+     *   - `ammount`: the rotation to apply.
+     *   - `point`:   the center of rotation.
+     */
+    #[inline]
+    fn rotated_wrt_point(&self, ammount: &AV, center: &LV) -> Self {
+        let mut res = self.translated(&-center);
+
+        res.rotate_by(ammount);
+        res.translate_by(center);
+
+        res
+    }
+
+    /// Rotates an object using a specific center of rotation.
+    ///
+    /// # Arguments
+    ///   * `m` - the object to be rotated
+    ///   * `ammount` - the rotation to be applied
+    ///   * `center` - the new center of rotation
+    #[inline]
+    fn rotate_wrt_point(&mut self, ammount: &AV, center: &LV) {
+        self.translate_by(&-center);
+        self.rotate_by(ammount);
+        self.translate_by(center);
+    }
+
+    /**
+     * Applies a rotation centered on the input translation.
+     *
+     * # Arguments
+     *   * `m` - the object to be rotated.
+     *   * `ammount` - the rotation to apply.
+     */
+    #[inline]
+    fn rotated_wrt_center(&self, ammount: &AV) -> Self {
+        self.rotated_wrt_point(ammount, &self.translation())
+    }
+
+    /**
+     * Applies a rotation centered on the input translation.
+     *
+     * # Arguments
+     *   * `m` - the object to be rotated.
+     *   * `ammount` - the rotation to apply.
+     */
+    #[inline]
+    fn rotate_wrt_center(&mut self, ammount: &AV) {
+        let center = self.translation();
+        self.rotate_wrt_point(ammount, &center)
+    }
+}
+
+impl<LV: Neg<LV>, AV, M: Rotation<AV> + Translation<LV>> RotationWithTranslation<LV, AV> for M;
diff --git a/src/traits/mat.rs b/src/traits/mat.rs
new file mode 100644
index 00000000..9e7585b6
--- /dev/null
+++ b/src/traits/mat.rs
@@ -0,0 +1,8 @@
+use traits::row::Row;
+use traits::col::Col;
+use traits::rlmul::{RMul, LMul};
+
+/// Trait of matrix. A matrix must have lines and columns.
+pub trait Mat<R, C> : Row<R> + Col<C> + RMul<R> + LMul<C> { }
+
+impl<M: Row<R> + Col<C> + RMul<R> + LMul<C>, R, C> Mat<R, C> for M;
diff --git a/src/traits/rotation.rs b/src/traits/rotation.rs
index 0f6b2bd6..aeba53e0 100644
--- a/src/traits/rotation.rs
+++ b/src/traits/rotation.rs
@@ -1,4 +1,4 @@
-use traits::translation::Translation;
+use traits::mat::Mat;
 
 /// Trait of object which represent a rotation, and to wich new rotations can
 /// be appended. A rotation is assumed to be an isomitry without translation
@@ -29,64 +29,9 @@ pub trait Rotate<V> {
     fn inv_rotate(&self, &V) -> V;
 }
 
-/// Utilities to make rotations with regard to a point different than the origin.
-// NOTE: we cannot call this an Isometry since an isometry really does not need to have a rotation
-// nor a translation (this can be a reflexion).
-pub trait RotationWithTranslation<LV: Neg<LV>, AV>: Rotation<AV> + Translation<LV> {
-    /**
-     * Applies a rotation centered on a specific point.
-     *
-     *   - `m`:       the object to be rotated.
-     *   - `ammount`: the rotation to apply.
-     *   - `point`:   the center of rotation.
-     */
-    #[inline]
-    fn rotated_wrt_point(&self, ammount: &AV, center: &LV) -> Self {
-        let mut res = self.translated(&-center);
-
-        res.rotate_by(ammount);
-        res.translate_by(center);
-
-        res
-    }
-
-    /// Rotates an object using a specific center of rotation.
-    ///
-    /// # Arguments
-    ///   * `m` - the object to be rotated
-    ///   * `ammount` - the rotation to be applied
-    ///   * `center` - the new center of rotation
-    #[inline]
-    fn rotate_wrt_point(&mut self, ammount: &AV, center: &LV) {
-        self.translate_by(&-center);
-        self.rotate_by(ammount);
-        self.translate_by(center);
-    }
-
-    /**
-     * Applies a rotation centered on the input translation.
-     *
-     * # Arguments
-     *   * `m` - the object to be rotated.
-     *   * `ammount` - the rotation to apply.
-     */
-    #[inline]
-    fn rotated_wrt_center(&self, ammount: &AV) -> Self {
-        self.rotated_wrt_point(ammount, &self.translation())
-    }
-
-    /**
-     * Applies a rotation centered on the input translation.
-     *
-     * # Arguments
-     *   * `m` - the object to be rotated.
-     *   * `ammount` - the rotation to apply.
-     */
-    #[inline]
-    fn rotate_wrt_center(&mut self, ammount: &AV) {
-        let center = self.translation();
-        self.rotate_wrt_point(ammount, &center)
-    }
+/// Trait of transformation having a rotation extractable as a rotation matrix.  This can typically
+/// be implemented by quaternions to convert them 
+pub trait RotationMatrix<LV, AV, R: Mat<LV, LV> + Rotation<AV>> : Rotation<AV> {
+    /// Gets the rotation matrix from this object.
+    fn to_rot_mat(&self) -> R;
 }
-
-impl<LV: Neg<LV>, AV, M: Rotation<AV> + Translation<LV>> RotationWithTranslation<LV, AV> for M;
diff --git a/src/traits/row.rs b/src/traits/row.rs
index 8e84250e..248d6f28 100644
--- a/src/traits/row.rs
+++ b/src/traits/row.rs
@@ -1,5 +1,7 @@
 /// Traits to access rows of a matrix or vector.
 pub trait Row<R> {
+    /// The number of columun of this matrix or vector.
+    fn num_rows(&self) -> uint;
     /// Reads the `i`-th row of `self`.
     fn row(&self, i: uint) -> R;
     /// Writes the `i`-th row of `self`.
diff --git a/src/vec_spec.rs b/src/vec_spec.rs
index 0b4ecf68..660b0631 100644
--- a/src/vec_spec.rs
+++ b/src/vec_spec.rs
@@ -41,6 +41,11 @@ impl<N: Neg<N> + Zero + Clone> CrossMatrix<Mat3<N>> for Vec3<N> {
 
 // FIXME: iplement this for all other vectors
 impl<N: Clone> Row<Vec1<N>> for Vec2<N> {
+    #[inline]
+    fn num_rows(&self) -> uint {
+        2
+    }
+
     #[inline]
     fn row(&self, i: uint) -> Vec1<N> {
         match i {