text: /*=========================================================================
  
    Program:   Visualization Toolkit
    Module:    vtkPolygonalSurfaceContourLineInterpolator.h
  
    Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
    All rights reserved.
    See Copyright.txt or http://www.kitware.com/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 notice for more information.
  
  =========================================================================*/
  // .NAME vtkPolygonalSurfaceContourLineInterpolator - Contour interpolator for to place points on polygonal surfaces.
  //
  // .SECTION Description
  // vtkPolygonalSurfaceContourLineInterpolator interpolates and places
  // contour points on polygonal surfaces. The class interpolates nodes by
  // computing a \em graph \em geodesic laying on the polygonal data. By \em
  // graph \em Geodesic, we mean that the line interpolating the two end
  // points traverses along on the mesh edges so as to form the shortest
  // path. A Dijkstra algorithm is used to compute the path. See
  // vtkDijkstraGraphGeodesicPath.
  //
  // The class is mean to be used in conjunction with
  // vtkPolygonalSurfacePointPlacer. The reason for this weak coupling is a
  // performance issue, both classes need to perform a cell pick, and
  // coupling avoids multiple cell picks (cell picks are slow).
  //
  // .SECTION Caveats
  // You should have computed cell normals for the input polydata.
  //
  // .SECTION See Also
  // vtkDijkstraGraphGeodesicPath, vtkPolyDataNormals
  
  #ifndef __vtkPolygonalSurfaceContourLineInterpolator_h
  #define __vtkPolygonalSurfaceContourLineInterpolator_h
  
  #include "vtkInteractionWidgetsModule.h" // For export macro
  #include "vtkPolyDataContourLineInterpolator.h"
  
  class vtkDijkstraGraphGeodesicPath;
  class vtkIdList;
  
  class VTKINTERACTIONWIDGETS_EXPORT vtkPolygonalSurfaceContourLineInterpolator : public vtkPolyDataContourLineInterpolator
  {
  public:
    // Description:
    // Standard methods for instances of this class.
    vtkTypeMacro(vtkPolygonalSurfaceContourLineInterpolator, vtkPolyDataContourLineInterpolator);
    void PrintSelf(ostream& os, vtkIndent indent);
  
    static vtkPolygonalSurfaceContourLineInterpolator *New();
  
    // Description:
    // Subclasses that wish to interpolate a line segment must implement this.
    // For instance vtkBezierContourLineInterpolator adds nodes between idx1
    // and idx2, that allow the contour to adhere to a bezier curve.
    virtual int InterpolateLine( vtkRenderer *ren,
                                 vtkContourRepresentation *rep,
                                 int idx1, int idx2 );
  
    // Description:
    // The interpolator is given a chance to update the node.
    // vtkImageContourLineInterpolator updates the idx'th node in the contour,
    // so it automatically sticks to edges in the vicinity as the user
    // constructs the contour.
    // Returns 0 if the node (world position) is unchanged.
    virtual int UpdateNode( vtkRenderer *,
                            vtkContourRepresentation *,
                            double * vtkNotUsed(node), int vtkNotUsed(idx) );
  
    // Description:
    // Height offset at which points may be placed on the polygonal surface.
    // If you specify a non-zero value here, be sure to have computed vertex
    // normals on your input polygonal data. (easily done with
    // vtkPolyDataNormals).
    vtkSetMacro( DistanceOffset, double );
    vtkGetMacro( DistanceOffset, double );
  
    // Description:
    // Get the contour point ids. These point ids correspond to those on the
    // polygonal surface
    void GetContourPointIds( vtkContourRepresentation *rep, vtkIdList *idList );
  
  protected:
    vtkPolygonalSurfaceContourLineInterpolator();
    ~vtkPolygonalSurfaceContourLineInterpolator();
  
    // Description:
    // Draw the polyline at a certain height (in the direction of the vertex
    // normal) above the polydata.
    double         DistanceOffset;
  
  private:
    vtkPolygonalSurfaceContourLineInterpolator(const vtkPolygonalSurfaceContourLineInterpolator&);  //Not implemented
    void operator=(const vtkPolygonalSurfaceContourLineInterpolator&);  //Not implemented
  
    // Cache the last used vertex id's (start and end).
    // If they are the same, don't recompute.
    vtkIdType      LastInterpolatedVertexIds[2];
  
    vtkDijkstraGraphGeodesicPath* DijkstraGraphGeodesicPath;
  };
  
  #endif
  