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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkSmoothErrorMetric.h,v $

  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 vtkSmoothErrorMetric - Objects that compute
// geometry-based error during cell tessellation according to
// some max angle.
//
// .SECTION Description
// It is a concrete error metric, based on a geometric criterium:
// a max angle between the chord passing through the midpoint and one of the
// endpoints and the other chord passing through the midpoint and the other
// endpoint of the edge. It is related to the flatness of an edge.
//
// .SECTION See Also
// vtkGenericCellTessellator vtkGenericSubdivisionErrorMetric

#ifndef __vtkSmoothErrorMetric_h
#define __vtkSmoothErrorMetric_h

#include "vtkGenericSubdivisionErrorMetric.h"

class vtkGenericDataSet;

class VTK_FILTERING_EXPORT vtkSmoothErrorMetric : public vtkGenericSubdivisionErrorMetric
{
public:
  // Description:
  // Construct the error metric with a default flatness threshold of 90.1
  // degrees.
  static vtkSmoothErrorMetric *New();
  
  // Description:
  // Standard VTK type and error macros.
  vtkTypeRevisionMacro(vtkSmoothErrorMetric,vtkGenericSubdivisionErrorMetric);
  void PrintSelf(ostream& os, vtkIndent indent);
  
  // Description:
  // Return the flatness threshold.
  // \post positive_result: result>90 && result<180
  double GetAngleTolerance();
  
  // Description:
  // Set the flatness threshold with an angle in degrees. Internally
  // compute the cosine. value is supposed to be in ]90,180[, if not
  // it is clamped in [90.1,179.9].
  // For instance 178  will give better result than 150.
  void SetAngleTolerance(double value);
  
  // Description:
  // Does the edge need to be subdivided according to the cosine between
  // the two chords passing through the mid-point and the endpoints?
  // The edge is defined by its `leftPoint' and its `rightPoint'.
  // `leftPoint', `midPoint' and `rightPoint' have to be initialized before
  // calling RequiresEdgeSubdivision().
  // Their format is global coordinates, parametric coordinates and
  // point centered attributes: xyx rst abc de...
  // `alpha' is the normalized abscissa of the midpoint along the edge.
  // (close to 0 means close to the left point, close to 1 means close to the
  // right point)
  // \pre leftPoint_exists: leftPoint!=0
  // \pre midPoint_exists: midPoint!=0
  // \pre rightPoint_exists: rightPoint!=0
  // \pre clamped_alpha: alpha>0 && alpha<1
  // \pre valid_size: sizeof(leftPoint)=sizeof(midPoint)=sizeof(rightPoint)
  //          =GetAttributeCollection()->GetNumberOfPointCenteredComponents()+6
  int RequiresEdgeSubdivision(double *leftPoint, double *midPoint,
                              double *rightPoint, double alpha);

  // Description:
  // Return the error at the mid-point. It will return an error relative to
  // the bounding box size if GetRelative() is true, a square absolute error
  // otherwise.
  // See RequiresEdgeSubdivision() for a description of the arguments.
  // \pre leftPoint_exists: leftPoint!=0
  // \pre midPoint_exists: midPoint!=0
  // \pre rightPoint_exists: rightPoint!=0
  // \pre clamped_alpha: alpha>0 && alpha<1
  // \pre valid_size: sizeof(leftPoint)=sizeof(midPoint)=sizeof(rightPoint)
  //          =GetAttributeCollection()->GetNumberOfPointCenteredComponents()+6
  // \post positive_result: result>=0
  double GetError(double *leftPoint, double *midPoint, double *rightPoint,
                  double alpha);
  
protected:
  vtkSmoothErrorMetric();
  virtual ~vtkSmoothErrorMetric();
  
  double AngleTolerance;
  double CosTolerance;
  
private:
  vtkSmoothErrorMetric(const vtkSmoothErrorMetric&);  // Not implemented.
  void operator=(const vtkSmoothErrorMetric&);  // Not implemented.
};

#endif
