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

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


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

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=========================================================================*/
// .NAME vtkLight - a virtual light for 3D rendering
// .SECTION Description
// vtkLight is a virtual light for 3D rendering. It provides methods to locate
// and point the light, turn it on and off, and set its brightness and color.
// In addition to the basic infinite distance point light source attributes,
// you also can specify the light attenuation values and cone angle.
// These attributes are only used if the light is a positional light.
// The default is a directional light (e.g. infinite point light source).
//
// Lights have a type that describes how the light should move with respect
// to the camera.  A Headlight is always located at the current camera position
// and shines on the camera's focal point.  A CameraLight also moves with
// the camera, but may not be coincident to it.  CameraLights are defined
// in a normalized coordinate space where the camera is located at (0, 0, 1),
// the camera is looking at (0, 0, 0), and up is (0, 1, 0).  Finally, a 
// SceneLight is part of the scene itself and does not move with the camera.
// (Renderers are responsible for moving the light based on its type.)
//
// Lights have a transformation matrix that describes the space in which
// they are positioned.  A light's world space position and focal point
// are defined by their local position and focal point, transformed by
// their transformation matrix (if it exists).

#ifndef __vtkLight_h
#define __vtkLight_h

#include "vtkObject.h"
#include "vtkMatrix4x4.h"

/* need for virtual function */
class vtkRenderer;

#define VTK_LIGHT_TYPE_HEADLIGHT    1
#define VTK_LIGHT_TYPE_CAMERA_LIGHT 2
#define VTK_LIGHT_TYPE_SCENE_LIGHT  3

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

  // Description:
  // Create a light with the focal point at the origin and its position
  // set to (0,0,1). The light is a SceneLight, its color is white, 
  // intensity=1, and the light is turned on. 
  static vtkLight *New();

  // Description:
  // Abstract interface to renderer. Each concrete subclass of vtkLight
  // will load its data into the graphics system in response to this method
  // invocation. The actual loading is performed by a vtkLightDevice
  // subclass, which will get created automatically.
  virtual void Render(vtkRenderer *, int) {};

  // Description:
  // Set/Get the color of the light.
  vtkSetVector3Macro(Color,float);
  vtkGetVectorMacro(Color,float,3);

  // Description:
  // Set/Get the position of the light.
  // Note: The position of the light is defined in the coordinate
  // space indicated by its transformation matrix (if it exists).
  // Thus, to get the light's world space position, use 
  // vtkGetTransformedPosition() instead of vtkGetPosition().
  vtkSetVector3Macro(Position,float);
  vtkGetVectorMacro(Position,float,3);
  void SetPosition(double *a) {this->SetPosition(a[0],a[1],a[2]);};
  
  // Description:
  // Set/Get the point at which the light is shining.
  // Note: The focal point of the light is defined in the coordinate
  // space indicated by its transformation matrix (if it exists).
  // Thus, to get the light's world space focal point, use 
  // vtkGetTransformedFocalPoint() instead of vtkGetFocalPoint().
  vtkSetVector3Macro(FocalPoint,float);
  vtkGetVectorMacro(FocalPoint,float,3);
  void SetFocalPoint(double *a) {this->SetFocalPoint(a[0],a[1],a[2]);};

  // Description:
  // Set/Get the brightness of the light (from one to zero).
  vtkSetMacro(Intensity,float);
  vtkGetMacro(Intensity,float);

  // Description:
  // Turn the light on or off.
  vtkSetMacro(Switch,int);
  vtkGetMacro(Switch,int);
  vtkBooleanMacro(Switch,int);

  // Description:
  // Turn positional lighting on or off.
  vtkSetMacro(Positional,int);
  vtkGetMacro(Positional,int);
  vtkBooleanMacro(Positional,int);

  // Description:
  // Set/Get the exponent of the cosine used in positional lighting.
  vtkSetMacro(Exponent,float);
  vtkGetMacro(Exponent,float);

  // Description:
  // Set/Get the lighting cone angle of a positional light in degrees.
  // A value of 180 indicates that you want no spot lighting effects
  // just a positional light.
  vtkSetMacro(ConeAngle,float);
  vtkGetMacro(ConeAngle,float);

  // Description:
  // Set/Get the quadratic attenuation constants. They are specified as
  // constant, linear, and quadratic, in that order.
  vtkSetVector3Macro(AttenuationValues,float);
  vtkGetVectorMacro(AttenuationValues,float,3);

  // Description:
  // Set/Get the light's transformation matrix.  If a matrix is set for
  // a light, the light's parameters (position and focal point) are 
  // transformed by the matrix before being rendered.
  vtkSetObjectMacro(TransformMatrix,vtkMatrix4x4);
  vtkGetObjectMacro(TransformMatrix,vtkMatrix4x4);

  // Description:
  // Get the position of the light, modified by the transformation matrix
  // (if it exists).
  void GetTransformedPosition(float &a0, float &a1, float &a2);
  void GetTransformedPosition(float a[3]);
  float *GetTransformedPosition();

  // Description:
  // Get the focal point of the light, modified by the transformation matrix
  // (if it exists).
  void GetTransformedFocalPoint(float &a0, float &a1, float &a2);
  void GetTransformedFocalPoint(float a[3]);
  float *GetTransformedFocalPoint();

  // Description:
  // Set the position and focal point of a light based on elevation and
  // azimuth.  The light is moved so it is shining from the given angle.
  // Angles are given in degrees.  If the light is a
  // positional light, it is made directional instead.
  void SetDirectionAngle(float elevation, float azimuth);
  void SetDirectionAngle(float ang[2]) { this->SetDirectionAngle(ang[0], ang[1]); };

  // Description:
  // Perform deep copy of this light.
  void DeepCopy(vtkLight *light);

  // Description:
  // Set/Get the type of the light.
  // A SceneLight is a light located in the world coordinate space.  A light
  // is initially created as a scene light.
  //
  // A Headlight is always located at the camera and is pointed at the 
  // camera's focal point.  The renderer is free to modify the position and
  // focal point of the camera at any time.
  //
  // A CameraLight is also attached to the camera, but is not necessarily
  // located at the camera's position.  CameraLights are defined in a 
  // coordinate space where the camera is located at (0, 0, 1), looking
  // towards (0, 0, 0) at a distance of 1, with up being (0, 1, 0).

  vtkSetMacro(LightType, int);
  vtkGetMacro(LightType, int);

  void SetLightTypeToHeadlight();
  void SetLightTypeToSceneLight();
  void SetLightTypeToCameraLight();

  // Description:
  // Query the type of the light.
  int LightTypeIsHeadlight();
  int LightTypeIsSceneLight();
  int LightTypeIsCameraLight();

  void ReadSelf(istream& is);
  void WriteSelf(ostream& os);
  
protected:
  vtkLight();
  ~vtkLight();
  vtkLight(const vtkLight&) {};
  void operator=(const vtkLight&) {};

  float FocalPoint[3];
  float Position[3];
  float Intensity;
  float Color[3];
  int   Switch;
  int   Positional;
  float Exponent;
  float ConeAngle;
  float AttenuationValues[3];
  vtkMatrix4x4 *TransformMatrix;
  float TransformedFocalPointReturn[3];
  float TransformedPositionReturn[3];
  int LightType;
};

#endif
