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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkInterpolatedVelocityField.h,v $
  Language:  C++
  Date:      $Date: 2001/10/11 13:36:16 $
  Version:   $Revision: 1.10 $


Copyright (c) 1993-2001 Ken Martin, Will Schroeder, Bill Lorensen 
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

 * Redistributions of source code must retain the above copyright notice,
   this list of conditions and the following disclaimer.

 * Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

 * Neither name of Ken Martin, Will Schroeder, or Bill Lorensen nor the names
   of any contributors may be used to endorse or promote products derived
   from this software without specific prior written permission.

 * Modified source versions must be plainly marked as such, and must not be
   misrepresented as being the original software.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS''
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

=========================================================================*/
// .NAME vtkInterpolatedVelocityField - Interface for obtaining
// interpolated velocity values
// .SECTION Description
// vtkInterpolatedVelocityField acts as a continuous velocity field
// by performing cell interpolation on the underlying vtkDataSet.
// This is a concrete sub-class of vtkFunctionSet with 
// NumberOfIndependentVariables = 4 (x,y,z,t) and 
// NumberOfFunctions = 3 (u,v,w). Normally, every time an evaluation
// is performed, the cell which contains the point (x,y,z) has to
// be found by calling FindCell. This is a computationally expansive 
// operation. In certain cases, the cell search can be avoided or shortened 
// by providing a guess for the cell id. For example, in streamline
// integration, the next evaluation is usually in the same or a neighbour
// cell. For this reason, vtkInterpolatedVelocityField stores the last
// cell id. If caching is turned on, it uses this id as the starting point.

// .SECTION Caveats
// vtkInterpolatedVelocityField is not thread safe. A new instance should
// be created by each thread.

// .SECTION See Also
// vtkFunctionSet vtkStreamer

#ifndef __vtkInterpolatedVelocityField_h
#define __vtkInterpolatedVelocityField_h

#include "vtkFunctionSet.h"
#include "vtkDataSet.h"
#include "vtkGenericCell.h"

class VTK_COMMON_EXPORT vtkInterpolatedVelocityField : public vtkFunctionSet
{
public:
  vtkTypeMacro(vtkInterpolatedVelocityField,vtkFunctionSet);
  virtual void PrintSelf(ostream& os, vtkIndent indent);

  // Description:
  // Construct a vtkInterpolatedVelocityField with no initial data set.
  // Caching is on. LastCellId is set to -1.
  static vtkInterpolatedVelocityField *New();

  // Description:
  // Evaluate the velocity field, f, at (x, y, z, t).
  // For now, t is ignored.
  virtual int FunctionValues(float* x, float* f);

  // Description:
  // Set / get the dataset used for the implicit function evaluation.
  virtual void SetDataSet(vtkDataSet* dataset);
  vtkGetObjectMacro(DataSet,vtkDataSet);

  // Description:
  // Return the cell id cached from last evaluation.
  vtkGetMacro(LastCellId, vtkIdType);
  vtkSetMacro(LastCellId, vtkIdType);

  // Description:
  // Set the last cell id to -1 so that the next search does not
  // start from the previous cell
  void ClearLastCellId() { this->LastCellId = -1; }

  // Description: 
  // Returns the interpolation weights cached from last evaluation
  // if the cached cell is valid (returns 1). Otherwise, it does not
  // change w and returns 0.
  int GetLastWeights(float* w);
  int GetLastLocalCoordinates(float pcoords[3]);

  // Description:
  // Turn caching on/off.
  vtkGetMacro(Caching, int);
  vtkSetMacro(Caching, int);
  vtkBooleanMacro(Caching, int);

  // Description:
  // Caching statistics.
  vtkGetMacro(CacheHit, int);
  vtkGetMacro(CacheMiss, int);
  
protected:
  vtkInterpolatedVelocityField();
  ~vtkInterpolatedVelocityField();

  vtkDataSet* DataSet;
  vtkGenericCell* GenCell; // last cell
  vtkGenericCell* Cell;
  float* Weights; // last weights
  float LastPCoords[3]; // last local coordinates
  vtkIdType LastCellId;
  int CacheHit;
  int CacheMiss;
  int Caching;
private:
  vtkInterpolatedVelocityField(const vtkInterpolatedVelocityField&);  // Not implemented.
  void operator=(const vtkInterpolatedVelocityField&);  // Not implemented.
};

#endif








