Import Jonathan's vtkgridfunction.hh

dune/vtkgridfunction.hh

+#ifndef VTK_BASIS_GRID_FUNCTION_HH
+#define VTK_BASIS_GRID_FUNCTION_HH
+
+#include <dune/grid/io/file/vtk/function.hh>
+
+/** \brief A VTK basis grid function.
+ *
+ *	This function "evaluates" by evaluating the global basis and
+ *interpolating the function values.
+ *  \tparam Basis   The global basis.
+ *  \tparam CoefficientType The vector type for the coefficients.
+*/
+template <class Basis, class CoefficientType>
+class VTKBasisGridFunction
+    : public VTKFunction<typename Basis::GridView::Grid> {
+
+  typedef VTKFunction<typename Basis::GridView::Grid> Base;
+  typedef typename Basis::LocalFiniteElement::Traits::LocalBasisType::Traits::
+      RangeType RangeType;
+
+public:
+  typedef typename Base::Entity Entity;
+  typedef typename Base::ctype ctype;
+  using Base::dim;
+
+  /** \brief Construct from given global basis, coefficient vector and name.
+   *
+   *  \param basis    The global basis.
+   *  \param v    A corresponding vector of coefficients.
+   *  \param s    A name of the function.
+   */
+  VTKBasisGridFunction(const Basis& basis, const CoefficientType& v,
+                       const std::string& s)
+      : basis_(basis), coeffs_(v), s(s_) {
+    if (v.size() != basis_.size())
+      DUNE_THROW(
+          IOError,
+          "VTKGridFunction: Coefficient vector is not matching the basis");
+  }
+
+  /** \brief Get the number of components the function has. */
+  virtual int ncomps() const { return CoefficientType::block_type::dimension; }
+
+  /** \brief Locally evaluate a component of the function.
+   *
+   *  \param comp The component to evaluate.
+   *  \param e    The element the local coordinates are taken from.
+   *  \param xi   The local coordinates where to evaluate the function.
+   */
+  virtual double evaluate(int comp, const Entity& e,
+                          const Dune::FieldVector<ctype, dim>& xi) const {
+    // evaluate the local shapefunctions
+    const typename Basis::LocalFiniteElement& localFE =
+        basis_.getLocalFiniteElement(e);
+    std::vector<RangeType> values(localFE.localBasis().size());
+    localFE.localBasis().evaluateFunction(xi, values);
+
+    // get the comp'th component
+    double rt = 0;
+    for (int i = 0; i < localFE.localBasis().size(); i++)
+      rt += values[i] * coeffs_[basis_.index(e, i)][comp];
+
+    return rt;
+  }
+
+  /** \brief Stupid function to return the name. */
+  virtual std::string name() const { return s_; }
+
+  /** \brief Destructor. */
+  virtual ~VTKGridFunction() {}
+
+private:
+  const Basis& basis_;
+  const CoefficientType& coeffs_;
+  std::string s_;
+};
+
+#endif