]> https://gitweb.dealii.org/ - dealii-svn.git/commitdiff
Update a number of comments.
authorwolf <wolf@0785d39b-7218-0410-832d-ea1e28bc413d>
Wed, 1 Jun 2005 14:48:40 +0000 (14:48 +0000)
committerwolf <wolf@0785d39b-7218-0410-832d-ea1e28bc413d>
Wed, 1 Jun 2005 14:48:40 +0000 (14:48 +0000)
git-svn-id: https://svn.dealii.org/trunk@10808 0785d39b-7218-0410-832d-ea1e28bc413d

deal.II/deal.II/include/fe/fe_values.h

index eec716d7b37bdb5644301bbb952ef61d1f45fff6..3cab860c5d26446e24d666440451077e9723658e 100644 (file)
@@ -165,6 +165,20 @@ class FEValuesData
                                      * class, see the general
                                      * documentation of this class
                                      * for more information.
+                                     *
+                                     * However, if this object refers
+                                     * to an FEFaceValues of
+                                     * FESubfaceValues object, then
+                                     * the JxW_values correspond to
+                                     * the Jacobian of the
+                                     * transformation of the face,
+                                     * not the cell, i.e. the
+                                     * dimensionality is that of a
+                                     * surface measure, not of a
+                                     * volume measure. In this case,
+                                     * it is computed from the
+                                     * boundary forms, rather than
+                                     * the Jacobian matrix.
                                      */
     std::vector<double>       JxW_values;
 
@@ -964,21 +978,27 @@ class FEValuesBase : protected FEValuesData<dim>
     const std::vector<Point<dim> > & get_quadrature_points () const;
 
                                     /**
-                                     * Mapped quadrature weight. This
-                                     * is the Jacobi determinant
-                                     * times the weight of the
-                                     *<tt>i</tt>th unit quadrature point.
+                                     * Mapped quadrature weight. If
+                                     * this object refers to a volume
+                                     * evaluation (i.e. the derived
+                                     * class is of type FEValues),
+                                     * then this is the Jacobi
+                                     * determinant times the weight
+                                     * of the *<tt>i</tt>th unit
+                                     * quadrature point.
                                      *
-                                     * On faces, this is the mapped
-                                     * surface element.
+                                     * For surface evaluations
+                                     * (i.e. classes FEFaceValues or
+                                     * FESubfaceValues), is the
+                                     * mapped surface element times
+                                     * the weight of the quadrature
+                                     * point.
                                      */
     double JxW (const unsigned int quadrature_point) const;
 
                                     /**
                                      * Pointer to the array holding
-                                     * the Jacobi determinant times the
-                                     * quadrature weight at the different
-                                     * quadrature points.
+                                     * the values returned by JxW().
                                      */
     const std::vector<double> & get_JxW_values () const;
     
@@ -1742,13 +1762,21 @@ class FEValues : public FEValuesBase<dim>
 
 
 /**
- * Extend the interface of FEValuesBase by surface values.
+ * Extend the interface of FEValuesBase to values that only make sense
+ * when evaluating something on the surface of a cell. All the data
+ * that is available in the interior of cells is also available here.
  *
  * On surfaces of mesh cells, normal vectors and boundary forms are
  * additional values that can be computed. This class provides the
  * interface to access those. Implementations are in derived classes
  * FEFaceValues and FESubfaceValues.
  *
+ * The boundary form is the cross product of the images of the unit
+ * tangential vectors. Therefore, it is the unit normal vector
+ * multiplied with the surface element. Since it may be cheaper to
+ * compute the boundary form immediately, use this value to integrate
+ * <tt>n.ds</tt>.
+ *
  * See FEValuesBase
  *
  *  @author Wolfgang Bangerth, 1998, Guido Kanschat, 2000, 2001

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