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

  Program:   Visualization Toolkit
  Module:    vtkHyperStreamline.h
  Language:  C++
  Date:      $Date$
  Version:   $Revision$


Copyright (c) 1993-2001 Ken Martin, Will Schroeder, Bill Lorensen 
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=========================================================================*/
// .NAME vtkHyperStreamline - generate hyperstreamline in arbitrary dataset
// .SECTION Description
// vtkHyperStreamline is a filter that integrates through a tensor field to 
// generate a hyperstreamline. The integration is along the maximum eigenvector
// and the cross section of the hyperstreamline is defined by the two other
// eigenvectors. Thus the shape of the hyperstreamline is "tube-like", with 
// the cross section being elliptical. Hyperstreamlines are used to visualize
// tensor fields.
//
// The starting point of a hyperstreamline can be defined in one of two ways. 
// First, you may specify an initial position. This is a x-y-z global 
// coordinate. The second option is to specify a starting location. This is 
// cellId, subId, and  cell parametric coordinates.
//
// The integration of the hyperstreamline occurs through the major eigenvector 
// field. IntegrationStepLength controls the step length within each cell 
// (i.e., this is the fraction of the cell length). The length of the 
// hyperstreamline is controlled by MaximumPropagationDistance. This parameter
// is the length of the hyperstreamline in units of distance. The tube itself 
// is composed of many small sub-tubes - NumberOfSides controls the number of 
// sides in the tube, and StepLength controls the length of the sub-tubes.
//
// Because hyperstreamlines are often created near regions of singularities, it
// is possible to control the scaling of the tube cross section by using a 
// logarithmic scale. Use LogScalingOn to turn this capability on. The Radius 
// value controls the initial radius of the tube.

// .SECTION See Also
// vtkTensorGlyph vtkStreamer

#ifndef __vtkHyperStreamline_h
#define __vtkHyperStreamline_h

#include "vtkDataSetToPolyDataFilter.h"

#define VTK_INTEGRATE_FORWARD 0
#define VTK_INTEGRATE_BACKWARD 1
#define VTK_INTEGRATE_BOTH_DIRECTIONS 2

class vtkHyperArray;

class VTK_EXPORT vtkHyperStreamline : public vtkDataSetToPolyDataFilter
{
public:
  vtkTypeMacro(vtkHyperStreamline,vtkDataSetToPolyDataFilter);
  void PrintSelf(ostream& os, vtkIndent indent);

  // Description:
  // Construct object with initial starting position (0,0,0); integration
  // step length 0.2; step length 0.01; forward integration; terminal
  // eigenvalue 0.0; number of sides 6; radius 0.5; and logarithmic scaling
  // off.
  static vtkHyperStreamline *New();

  // Description:
  // Specify the start of the hyperstreamline in the cell coordinate system. 
  // That is, cellId and subId (if composite cell), and parametric coordinates.
  void SetStartLocation(int cellId, int subId, float pcoords[3]);

  // Description:
  // Specify the start of the hyperstreamline in the cell coordinate system. 
  // That is, cellId and subId (if composite cell), and parametric coordinates.
  void SetStartLocation(int cellId, int subId, float r, float s, float t);

  // Description:
  // Get the starting location of the hyperstreamline in the cell coordinate
  // system. Returns the cell that the starting point is in.
  int GetStartLocation(int& subId, float pcoords[3]);

  // Description:
  // Specify the start of the hyperstreamline in the global coordinate system. 
  // Starting from position implies that a search must be performed to find 
  // initial cell to start integration from.
  void SetStartPosition(float x[3]);

  // Description:
  // Specify the start of the hyperstreamline in the global coordinate system. 
  // Starting from position implies that a search must be performed to find 
  // initial cell to start integration from.
  void SetStartPosition(float x, float y, float z);

  // Description:
  // Get the start position of the hyperstreamline in global x-y-z coordinates.
  float *GetStartPosition();

  // Description:
  // Set / get the maximum length of the hyperstreamline expressed as absolute
  // distance (i.e., arc length) value.
  vtkSetClampMacro(MaximumPropagationDistance,float,0.0,VTK_LARGE_FLOAT);
  vtkGetMacro(MaximumPropagationDistance,float);

  // Description:
  // Use the major eigenvector field as the vector field through which to 
  // integrate. The major eigenvector is the eigenvector whose corresponding
  // eigenvalue is closest to positive infinity.
  void IntegrateMajorEigenvector();

  // Description:
  // Use the major eigenvector field as the vector field through which to 
  // integrate. The major eigenvector is the eigenvector whose corresponding
  // eigenvalue is between the major and minor eigenvalues.
  void IntegrateMediumEigenvector();

  // Description:
  // Use the major eigenvector field as the vector field through which to 
  // integrate. The major eigenvector is the eigenvector whose corresponding
  // eigenvalue is closest to negative infinity.
  void IntegrateMinorEigenvector();

  // Description:
  // Set / get a nominal integration step size (expressed as a fraction of
  // the size of each cell).
  vtkSetClampMacro(IntegrationStepLength,float,0.001,0.5);
  vtkGetMacro(IntegrationStepLength,float);

  // Description:
  // Set / get the length of a tube segment composing the hyperstreamline. The
  // length is specified as a fraction of the diagonal length of the input
  // bounding box.
  vtkSetClampMacro(StepLength,float,0.000001,1.0);
  vtkGetMacro(StepLength,float);

  // Description:
  // Specify the direction in which to integrate the hyperstreamline.
  vtkSetClampMacro(IntegrationDirection,int,
                  VTK_INTEGRATE_FORWARD,VTK_INTEGRATE_BOTH_DIRECTIONS);
  vtkGetMacro(IntegrationDirection,int);
  void SetIntegrationDirectionToForward()
    {this->SetIntegrationDirection(VTK_INTEGRATE_FORWARD);};
  void SetIntegrationDirectionToBackward()
    {this->SetIntegrationDirection(VTK_INTEGRATE_BACKWARD);};
  void SetIntegrationDirectionToIntegrateBothDirections()
    {this->SetIntegrationDirection(VTK_INTEGRATE_BOTH_DIRECTIONS);};

  // Description:
  // Set/get terminal eigenvalue.  If major eigenvalue falls below this
  // value, hyperstreamline terminates propagation.
  vtkSetClampMacro(TerminalEigenvalue,float,0.0,VTK_LARGE_FLOAT);
  vtkGetMacro(TerminalEigenvalue,float);

  // Description:
  // Set / get the number of sides for the hyperstreamlines. At a minimum,
  // number of sides is 3.
  vtkSetClampMacro(NumberOfSides,int,3,VTK_LARGE_INTEGER);
  vtkGetMacro(NumberOfSides,int);

  // Description:
  // Set / get the initial tube radius. This is the maximum "elliptical"
  // radius at the beginning of the tube. Radius varies based on ratio of
  // eigenvalues.  Note that tube section is actually elliptical and may
  // become a point or line in cross section in some cases.
  vtkSetClampMacro(Radius,float,0.0001,VTK_LARGE_FLOAT);
  vtkGetMacro(Radius,float);

  // Description:
  // Turn on/off logarithmic scaling. If scaling is on, the log base 10
  // of the computed eigenvalues are used to scale the cross section radii.
  vtkSetMacro(LogScaling,int);
  vtkGetMacro(LogScaling,int);
  vtkBooleanMacro(LogScaling,int);

protected:
  vtkHyperStreamline();
  ~vtkHyperStreamline();
  vtkHyperStreamline(const vtkHyperStreamline&) {};
  void operator=(const vtkHyperStreamline&) {};

  // Integrate data
  void Execute();
  void BuildTube();

  // Flag indicates where streamlines start from (either position or location)
  int StartFrom;

  // Starting from cell location
  int StartCell;
  int StartSubId;
  float StartPCoords[3];

  // starting from global x-y-z position
  float StartPosition[3];

  //array of hyperstreamlines
  vtkHyperArray *Streamers;
  int NumberOfStreamers;

  // length of hyperstreamline in absolute distance
  float MaximumPropagationDistance;

  // integration direction
  int IntegrationDirection;

  // the length (fraction of cell size) of integration steps
  float IntegrationStepLength;

  // the length of the tube segments composing the hyperstreamline
  float StepLength;

  // terminal propagation speed
  float TerminalEigenvalue;

  // number of sides of tube
  int NumberOfSides;

  // maximum radius of tube
  float Radius;

  // boolean controls whether scaling is clamped
  int LogScaling;

  // which eigenvector to use as integration vector field
  int IntegrationEigenvector;
};

#endif


