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

  Program:   Visualization Toolkit
  Module:    vtkProp3DFollower.h

  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 vtkProp3DFollower - a vtkProp3D that always faces the camera
// .SECTION Description
// vtkProp3DFollower is a type of vtkProp3D that always faces the camera.
// More specifically it will not change its position or scale,
// but it will continually update its orientation so that it is right side
// up and facing the camera. This is typically used for complex billboards
// or props that need to face the viewer at all times.
//
// Note: All of the transformations that can be made to a vtkProp3D will take
// effect with the follower. Thus, if you change the orientation of the
// follower by 90 degrees, then it will follow the camera, but be off by 90
// degrees.

// .SECTION see also
// vtkFollower vtkProp3D vtkActor vtkCamera

#ifndef __vtkProp3DFollower_h
#define __vtkProp3DFollower_h

#include "vtkProp3D.h"

class vtkCamera;
class vtkMapper;


class VTK_RENDERING_EXPORT vtkProp3DFollower : public vtkProp3D
{
 public:
  // Description:
  // Creates a follower with no camera set.
  static vtkProp3DFollower *New();

  // Description:
  // Standard VTK methods for type and printing.
  vtkTypeMacro(vtkProp3DFollower,vtkProp3D);
  void PrintSelf(ostream& os, vtkIndent indent);

  // Description:
  // Set/Get the vtkProp3D to control (i.e., face the camera).
  virtual void SetProp3D(vtkProp3D *prop);
  virtual vtkProp3D *GetProp3D();

  // Description:
  // Set/Get the camera to follow. If this is not set, then the follower
  // won't know what to follow and will act like a normal vtkProp3D.
  virtual void SetCamera(vtkCamera*);
  vtkGetObjectMacro(Camera,vtkCamera);

  // Description:
  // This causes the actor to be rendered. It in turn will render the actor's
  // property, texture map and then mapper. If a property hasn't been
  // assigned, then the actor will create one automatically.
  virtual int RenderOpaqueGeometry(vtkViewport *viewport);
  virtual int RenderTranslucentPolygonalGeometry(vtkViewport *viewport);
  virtual int RenderVolumetricGeometry(vtkViewport *viewport);

  // Description:
  // Does this prop have some translucent polygonal geometry?
  virtual int HasTranslucentPolygonalGeometry();

  // Description:
  // Release any graphics resources associated with this vtkProp3DFollower.
  virtual void ReleaseGraphicsResources(vtkWindow*);

  // Description:
  // Generate the matrix based on ivars. This method overloads its superclasses
  // ComputeMatrix() method due to the special vtkProp3DFollower matrix operations.
  virtual void ComputeMatrix();

  // Description:
  // Shallow copy of a follower. Overloads the virtual vtkProp method.
  void ShallowCopy(vtkProp *prop);

  // Description:
  // Return the bounds of this vtkProp3D.
  virtual double *GetBounds();

  // Description:
  // Overload vtkProp's method for setting up assembly paths. See
  // the documentation for vtkProp.
  void InitPathTraversal();
  virtual vtkAssemblyPath *GetNextPath();

protected:
  vtkProp3DFollower();
  ~vtkProp3DFollower();

  vtkCamera *Camera;
  vtkProp3D  *Device;

private:
  vtkProp3DFollower(const vtkProp3DFollower&);  // Not implemented.
  void operator=(const vtkProp3DFollower&);  // Not implemented.

  //Internal matrices to avoid New/Delete for performance reasons
  vtkMatrix4x4 *InternalMatrix;

};

#endif
