--- /tmp/tmpLG3iFL-meld/Eigen/src/Geometry/Quaternion.h
+++ /home/strasdat/src/ScaViSLAM/EXTERNAL/eigen3.1/Eigen/src/Geometry/Quaternion.h
@@ -152,6 +152,9 @@
   /** \returns an equivalent 3x3 rotation matrix */
   Matrix3 toRotationMatrix() const;
 
+  /** \returns an equivalent 3x3 rotation and scaling matrix */
+  Matrix3 toRotationAndScalingMatrix() const;
+
   /** \returns the quaternion which transform \a a into \a b through a rotation */
   template<typename Derived1, typename Derived2>
   Derived& setFromTwoVectors(const MatrixBase<Derived1>& a, const MatrixBase<Derived2>& b);
@@ -585,6 +588,53 @@
   res.coeffRef(2,0) = txz-twy;
   res.coeffRef(2,1) = tyz+twx;
   res.coeffRef(2,2) = Scalar(1)-(txx+tyy);
+
+  return res;
+}
+
+/** Convert the quaternion to a 3x3 rotation and scaling matrix.
+  * Thus, the result is s*R, with s being a positive scalar and
+  * R an orthogonal matrix with det(R)=1.
+  */
+template<class Derived>
+inline typename QuaternionBase<Derived>::Matrix3
+QuaternionBase<Derived>::toRotationAndScalingMatrix(void) const
+{
+  // NOTE if inlined, then gcc 4.2 and 4.4 get rid of the temporary (not gcc 4.3 !!)
+  // if not inlined then the cost of the return by value is huge ~ +35%,
+  // however, not inlining this function is an order of magnitude slower, so
+  // it has to be inlined, and so the return by value is not an issue
+  Matrix3 res;
+
+  const Scalar nrm = norm();
+  if (nrm == 0)
+  {
+    res.setZero();
+    return res;
+  }
+  const Scalar two_by_norm = 2./nrm;
+  const Scalar tx  = two_by_norm*this->x();
+  const Scalar ty  = two_by_norm*this->y();
+  const Scalar tz  = two_by_norm*this->z();
+  const Scalar twx = tx*this->w();
+  const Scalar twy = ty*this->w();
+  const Scalar twz = tz*this->w();
+  const Scalar txx = tx*this->x();
+  const Scalar txy = ty*this->x();
+  const Scalar txz = tz*this->x();
+  const Scalar tyy = ty*this->y();
+  const Scalar tyz = tz*this->y();
+  const Scalar tzz = tz*this->z();
+
+  res.coeffRef(0,0) = nrm-(tyy+tzz);
+  res.coeffRef(0,1) = txy-twz;
+  res.coeffRef(0,2) = txz+twy;
+  res.coeffRef(1,0) = txy+twz;
+  res.coeffRef(1,1) = nrm-(txx+tzz);
+  res.coeffRef(1,2) = tyz-twx;
+  res.coeffRef(2,0) = txz-twy;
+  res.coeffRef(2,1) = tyz+twx;
+  res.coeffRef(2,2) = nrm-(txx+tyy);
 
   return res;
 }