Add some documentation

dune/fufem/utilities/dirichletbcassembler.hh

@@ -21,6 +21,23 @@
 /** \brief This class provides a method to assemble the leaf Dirichlet values and dofs from coarse ones.
  *
  *         So far only P1 elements are supported.
+ *
+ *  To use this assembler the parameter file should provide:
+ *
+ *  1. A patch file determining which part of the boundary is considered, either
+ *
+ *    amiraPatchFile - A bitfield in Amira format
+ *
+ *  or a list of criterions, see BoundaryPatchFactory for more details.
+ *
+ *  2. A file containing the nodal interpolation of the boundary function, either
+ *
+ *    amiraValuesFile - A surface vector field in Amira format
+ * or
+ *    constantValues - A Vector that represents a constant field
+ *
+ * If none are given, then a homogeneous zero-field is used.
+ *
  * */
 template <class GridType>
 class DirichletBCAssembler