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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkVisibilitySort.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.

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

/*
 * Copyright 2003 Sandia Corporation.
 * Under the terms of Contract DE-AC04-94AL85000, there is a non-exclusive
 * license for use of this work by or on behalf of the
 * U.S. Government. Redistribution and use in source and binary forms, with
 * or without modification, are permitted provided that this Notice and any
 * statement of authorship are reproduced on all copies.
 */

// .NAME vtkVisibilitySort - Abstract class that can sort cell data along a viewpoint.
//
// .SECTION Description
// vtkVisibilitySort encapsulates a method for depth sorting the cells of a
// vtkDataSet for a given viewpoint.  It should be noted that subclasses
// are not required to give an absolutely correct sorting.  Many types of
// unstructured grids may have sorting cycles, meaning that there is no
// possible correct sorting.  Some subclasses also only give an approximate
// sorting in the interest of speed.
//
// .SECTION Note
// The Input field of this class tends to causes reference cycles.  To help
// break these cycles, garbage collection is enabled on this object and the
// input parameter is traced.  For this to work, though, an object in the
// loop holding the visibility sort should also report that to the garbage
// collector.
//

#ifndef __vtkVisibilitySort_h
#define __vtkVisibilitySort_h

#include "vtkObject.h"

class vtkIdTypeArray;
class vtkDataSet;
class vtkMatrix4x4;
class vtkCamera;

class VTK_GRAPHICS_EXPORT vtkVisibilitySort : public vtkObject
{
public:
  vtkTypeRevisionMacro(vtkVisibilitySort, vtkObject);
  virtual void PrintSelf(ostream &os, vtkIndent indent);

  // Description:
  // To facilitate incremental sorting algorithms, the cells are retrieved
  // in an iteration process.  That is, call InitTraversal to start the
  // iteration and call GetNextCells to get the cell IDs in order.
  // However, for efficiencies sake, GetNextCells returns an ordered list
  // of several id's in once call (but not necessarily all).  GetNextCells
  // will return NULL once the entire sorted list is output.  The
  // vtkIdTypeArray returned from GetNextCells is a cached array, so do not
  // delete it.  At the same note, do not expect the array to be valid
  // after subsequent calls to GetNextCells.
  virtual void InitTraversal() = 0;
  virtual vtkIdTypeArray *GetNextCells() = 0;

  // Description:
  // Set/Get the maximum number of cells that GetNextCells will return
  // in one invocation.
  vtkSetClampMacro(MaxCellsReturned, int, 1, VTK_LARGE_INTEGER);
  vtkGetMacro(MaxCellsReturned, int);

  // Description:
  // Set/Get the matrix that transforms from object space to world space.
  // Generally, you get this matrix from a call to GetMatrix of a vtkProp3D
  // (vtkActor).
  virtual void SetModelTransform(vtkMatrix4x4 *mat);
  vtkGetObjectMacro(ModelTransform, vtkMatrix4x4);

  vtkGetObjectMacro(InverseModelTransform, vtkMatrix4x4);

  // Description:
  // Set/Get the camera that specifies the viewing parameters.
  virtual void SetCamera(vtkCamera *camera);
  vtkGetObjectMacro(Camera, vtkCamera);

  // Description:
  // Set/Get the data set containing the cells to sort.
  virtual void SetInput(vtkDataSet *data);
  vtkGetObjectMacro(Input, vtkDataSet);

  // Description:
  // Set/Get the sorting direction.  Be default, the direction is set
  // to back to front.
  vtkGetMacro(Direction, int);
  vtkSetMacro(Direction, int);
  void SetDirectionToBackToFront() { this->SetDirection(BACK_TO_FRONT); }
  void SetDirectionToFrontToBack() { this->SetDirection(FRONT_TO_BACK); }

//BTX
  enum { BACK_TO_FRONT, FRONT_TO_BACK };
//ETX

  // Description:
  // Overwritten to enable garbage collection.
  virtual void Register(vtkObjectBase *o);
  virtual void UnRegister(vtkObjectBase *o);

protected:
  vtkVisibilitySort();
  virtual ~vtkVisibilitySort();

  vtkTimeStamp LastSortTime;

  vtkMatrix4x4 *ModelTransform;
  vtkMatrix4x4 *InverseModelTransform;
  vtkCamera *Camera;
  vtkDataSet *Input;

  int MaxCellsReturned;

  int Direction;

  virtual void ReportReferences(vtkGarbageCollector *collector);

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

#endif //__vtkVisibilitySort_h

