/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkFEMLoadEdge.h,v $
  Language:  C++
  Date:      $Date: 2003/09/10 14:29:42 $
  Version:   $Revision: 1.8 $

  Copyright (c) Insight Software Consortium. All rights reserved.
  See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even 
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR 
     PURPOSE.  See the above copyright notices for more information.

=========================================================================*/

#ifndef __itkFEMLoadEdge_h
#define __itkFEMLoadEdge_h

#include "itkFEMLoadElementBase.h"
#include "vnl/vnl_matrix.h"

namespace itk {
namespace fem {




/**
 * \class LoadEdge
 * \brief A generic load that can be applied to an edge of the element.
 *
 * Can also be used to apply natural (Neumann) boundary condition on the
 * edge of the element. In this case m_Edge defines the edge or surfance
 * of the element on which the BC exists and matrix m_Force holds the actual
 * prescribed values of the BC.
 */
class LoadEdge : public LoadElement
{
FEM_CLASS(LoadEdge,LoadElement)
public:
  /** 
   * Read a Load object from input stream.
   * We need arrays of elements and nodes to do that.
   */
  virtual void Read( std::istream& f, void* info );

  /**
   * Write a Load object to the output stream
   */
  virtual void Write( std::ostream& f ) const;

public:
  /**
   * Local number of the edge (face) of the element on which the load acts.
   * Check the corresponding element class for more info on edge numbering.
   */
  int m_Edge;

  /**
   * An edge force matrix. This matrix specifies nodal forces on all
   * nodes within the edge or face on which the load acts. Each nodal
   * force is decomposed into several components (check the documentation 
   * inside the element class). In case of 2D elements this components
   * are normal (1st component) and tangential (2nd component) force
   * acting on the edge of the element. A positive normal load acts in
   * a direction INTO the element. A positive tangential load acts in
   * an ANTICLOCKWISE direction with respect to the loaded elemenet.
   * Each nodal force is stored in a column of the matrix. The number
   * of columns in the Force matrix must correspond to the number of
   * nodes that define the edge (face...). The force is interpolated
   * over the entire edge (face) by using the shape functions of the
   * element. Again check the documentation of the element class to which
   * the force is applied.
   */
  vnl_matrix<Float> m_Force;

};

FEM_CLASS_INIT(LoadEdge)




}} // end namespace itk::fem

#endif // #ifndef __itkFEMLoadEdge_h
