VTK-5.0.0/Graphics/vtkPolyDataNormals.h

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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkPolyDataNormals.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 vtkPolyDataNormals - compute normals for polygonal mesh
// .SECTION Description
// vtkPolyDataNormals is a filter that computes point normals for a polygonal 
// mesh. The filter can reorder polygons to insure consistent orientation
// across polygon neighbors. Sharp edges can be split and points duplicated
// with separate normals to give crisp (rendered) surface definition. It is
// also possible to globally flip the normal orientation.
//
// The algorithm works by determining normals for each polygon and then
// averaging them at shared points. When sharp edges are present, the edges
// are split and new points generated to prevent blurry edges (due to 
// Gouraud shading).

// .SECTION Caveats
// Normals are computed only for polygons and triangle strips. Normals are
// not computed for lines or vertices.
//
// Triangle strips are broken up into triangle polygons. You may want to 
// restrip the triangles.

#ifndef __vtkPolyDataNormals_h
#define __vtkPolyDataNormals_h

#include "vtkPolyDataAlgorithm.h"

class vtkFloatArray;
class vtkIdList;
class vtkPolyData;

class VTK_GRAPHICS_EXPORT vtkPolyDataNormals : public vtkPolyDataAlgorithm
{
public:
  vtkTypeRevisionMacro(vtkPolyDataNormals,vtkPolyDataAlgorithm);
  void PrintSelf(ostream& os, vtkIndent indent);

  // Description:
  // Construct with feature angle=30, splitting and consistency turned on, 
  // flipNormals turned off, and non-manifold traversal turned on.
  // ComputePointNormals is on and ComputeCellNormals is off.
  static vtkPolyDataNormals *New();

  // Description:
  // Specify the angle that defines a sharp edge. If the difference in
  // angle across neighboring polygons is greater than this value, the
  // shared edge is considered "sharp".
  vtkSetClampMacro(FeatureAngle,double,0.0,180.0);
  vtkGetMacro(FeatureAngle,double);

  // Description:
  // Turn on/off the splitting of sharp edges.
  vtkSetMacro(Splitting,int);
  vtkGetMacro(Splitting,int);
  vtkBooleanMacro(Splitting,int);

  // Description:
  // Turn on/off the enforcement of consistent polygon ordering.
  vtkSetMacro(Consistency,int);
  vtkGetMacro(Consistency,int);
  vtkBooleanMacro(Consistency,int);

  // Description:
  // Turn on/off the automatic determination of correct normal
  // orientation. NOTE: This assumes a completely closed surface
  // (i.e. no boundary edges) and no non-manifold edges. If these
  // constraints do not hold, all bets are off. This option adds some
  // computational complexity, and is useful if you don't want to have
  // to inspect the rendered image to determine whether to turn on the 
  // FlipNormals flag. However, this flag can work with the FlipNormals 
  // flag, and if both are set, all the normals in the output will 
  // point "inward".
  vtkSetMacro(AutoOrientNormals, int);
  vtkGetMacro(AutoOrientNormals, int);
  vtkBooleanMacro(AutoOrientNormals, int);

  // Description:
  // Turn on/off the computation of point normals.
  vtkSetMacro(ComputePointNormals,int);
  vtkGetMacro(ComputePointNormals,int);
  vtkBooleanMacro(ComputePointNormals,int);

  // Description:
  // Turn on/off the computation of cell normals.
  vtkSetMacro(ComputeCellNormals,int);
  vtkGetMacro(ComputeCellNormals,int);
  vtkBooleanMacro(ComputeCellNormals,int);

  // Description:
  // Turn on/off the global flipping of normal orientation. Flipping
  // reverves the meaning of front and back for Frontface and Backface
  // culling in vtkProperty.  Flipping modifies both the normal
  // direction and the order of a cell's points.
  vtkSetMacro(FlipNormals,int);
  vtkGetMacro(FlipNormals,int);
  vtkBooleanMacro(FlipNormals,int);

  // Description:
  // Turn on/off traversal across non-manifold edges. This will prevent
  // problems where the consistency of polygonal ordering is corrupted due
  // to topological loops.
  vtkSetMacro(NonManifoldTraversal,int);
  vtkGetMacro(NonManifoldTraversal,int);
  vtkBooleanMacro(NonManifoldTraversal,int);
  
protected:
  vtkPolyDataNormals();
  ~vtkPolyDataNormals() {};

  // Usual data generation method
  int RequestData(vtkInformation *, vtkInformationVector **, vtkInformationVector *);

  double FeatureAngle;
  int Splitting;
  int Consistency;
  int FlipNormals;
  int AutoOrientNormals;
  int NonManifoldTraversal;
  int ComputePointNormals;
  int ComputeCellNormals;
  int NumFlips;

private:
  vtkIdList *Wave;
  vtkIdList *Wave2;
  vtkIdList *CellIds;
  vtkIdList *Map;
  vtkPolyData *OldMesh;
  vtkPolyData *NewMesh;
  int *Visited;
  vtkFloatArray *PolyNormals;
  double CosAngle;

  // Uses the list of cell ids (this->Wave) to propagate a wave of
  // checked and properly ordered polygons.
  void TraverseAndOrder(void);

  // Check the point id give to see whether it lies on a feature
  // edge. If so, split the point (i.e., duplicate it) to topologically
  // separate the mesh.
  void MarkAndSplit(vtkIdType ptId);

private:
  vtkPolyDataNormals(const vtkPolyDataNormals&);  // Not implemented.
  void operator=(const vtkPolyDataNormals&);  // Not implemented.
};

#endif