Added function for shape matrix interpolation.

NumLib/Function/Interpolation.h

+#ifndef NUMLIB_INTERPOLATION_H
+#define NUMLIB_INTERPOLATION_H
+
+namespace NumLib
+{
+
+/**
+ * Interpolates variables given at element nodes according to the given shape matrix.
+ *
+ * This function simply does the usual finite-element interpolation, i.e. multiplication
+ * of nodal values with the shape function.
+ *
+ * @param nodal_values   vector of nodal values
+ * @param shape_matrix_N shape matrix of the point to which will be interpolated
+ * @param num_nodal_dof  number of nodal variables that will be interpolated
+ * @param interpolated_values array of addresses to which the interpolated values will be written
+ *
+ * The size of interpolated_values must be equal to num_nodal_dof.
+ */
+template<typename NodalValues, typename ShapeMatrix>
+void shapeFunctionInterpolate(
+        const NodalValues& nodal_values,
+        const ShapeMatrix& shape_matrix_N,
+        const unsigned num_nodal_dof,
+        double** interpolated_values
+        )
+{
+    auto const num_nodes = shape_matrix_N.size();
+
+    for (unsigned d=0; d<num_nodal_dof; ++d)
+    {
+        *interpolated_values[d] = 0.0;
+
+        for (unsigned n=0; n<num_nodes; ++n)
+        {
+            *interpolated_values[d] += nodal_values[d*num_nodes+n] * shape_matrix_N(n);
+        }
+    }
+}
+
+}
+
+#endif // NUMLIB_INTERPOLATION_H