* Creates a new MEDCouplingFieldDouble holding Skew factor values of all
* cells of \a this 2D mesh in 3D space. Currently cells of the following types are
* treated: INTERP_KERNEL::NORM_QUAD4.
+ * The skew is computed as follow for a quad with points (a,b,c,d): let
+ * \f$u=\vec{ab}+\vec{dc}\f$ and \f$v=\vec{ac}+\vec{bd}\f$
+ * then the skew is computed as:
+ * \f$s=\frac{u}{|u|}\cdot\frac{v}{|v|}\f$
+ *
* For a cell of other type an exception is thrown.
* \return MEDCouplingFieldDouble * - a new instance of MEDCouplingFieldDouble on
* cells and one time, lying on \a this mesh. The caller is to delete this