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

  Program:   Visualization Toolkit
  Module:    vtkShadowMapPass.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.

=========================================================================*/
/**
 * @class   vtkShadowMapBakerPass
 * @brief   Implement a builder of shadow map pass.
 *
 * Bake a list of shadow maps, once per spot light.
 * It work in conjunction with the vtkShadowMapPass, which uses the
 * shadow maps for rendering the opaque geometry (a technique to render hard
 * shadows in hardware).
 *
 * This pass expects an initialized depth buffer and color buffer.
 * Initialized buffers means they have been cleared with farest z-value and
 * background color/gradient/transparent color.
 * An opaque pass may have been performed right after the initialization.
 *
 *
 *
 * Its delegate is usually set to a vtkOpaquePass.
 *
 * @par Implementation:
 * The first pass of the algorithm is to generate a shadow map per light
 * (depth map from the light point of view) by rendering the opaque objects
 * with the vtkShadowMapBakerPass::OCCLUDER property keys.
 * The second pass is to render the opaque objects with the vtkShadowMap::RECEIVER keys.
 *
 * @sa
 * vtkRenderPass, vtkOpaquePass, vtkShadowMapPass
*/

#ifndef vtkShadowMapBakerPass_h
#define vtkShadowMapBakerPass_h

#include "vtkRenderingOpenGLModule.h" // For export macro
#include "vtkRenderPass.h"

class vtkOpenGLRenderWindow;
class vtkInformationIntegerKey;
class vtkCamera;
class vtkLight;
class vtkFrameBufferObject;
class vtkShadowMapBakerPassTextures; // internal
class vtkShadowMapBakerPassLightCameras; // internal

class VTKRENDERINGOPENGL_EXPORT vtkShadowMapBakerPass : public vtkRenderPass
{
public:
  static vtkShadowMapBakerPass *New();
  vtkTypeMacro(vtkShadowMapBakerPass,vtkRenderPass);
  void PrintSelf(ostream& os, vtkIndent indent) VTK_OVERRIDE;

  /**
   * If this key exists on the PropertyKeys of a prop, the prop is viewed as a
   * light occluder (ie it casts shadows). This key is not mutually exclusive
   * with the RECEIVER() key.
   */
  static vtkInformationIntegerKey *OCCLUDER();

  // If this key exists on the Propertykeys of a prop, the prop is viewed as a
  // light/shadow receiver. This key is not mutually exclusive with the
  // OCCLUDER() key.
  static vtkInformationIntegerKey *RECEIVER();

  /**
   * Perform rendering according to a render state \p s.
   * \pre s_exists: s!=0
   */
  void Render(const vtkRenderState *s) VTK_OVERRIDE;

  /**
   * Release graphics resources and ask components to release their own
   * resources.
   * \pre w_exists: w!=0
   */
  void ReleaseGraphicsResources(vtkWindow *w) VTK_OVERRIDE;

  //@{
  /**
   * Delegate for rendering the opaque polygonal geometry.
   * If it is NULL, nothing will be rendered and a warning will be emitted.
   * It is usually set to a vtkCameraPass with a sequence of
   * vtkLightPass/vtkOpaquePass.
   * Initial value is a NULL pointer.
   */
  vtkGetObjectMacro(OpaquePass,vtkRenderPass);
  virtual void SetOpaquePass(vtkRenderPass *opaquePass);
  //@}

  //@{
  /**
   * Delegate for compositing of the shadow maps across processors.
   * If it is NULL, there is no z compositing.
   * It is usually set to a vtkCompositeZPass (Parallel package).
   * Initial value is a NULL pointer.
   */
  vtkGetObjectMacro(CompositeZPass,vtkRenderPass);
  virtual void SetCompositeZPass(vtkRenderPass *compositeZPass);
  //@}

  //@{
  /**
   * Set/Get the number of pixels in each dimension of the shadow maps
   * (shadow maps are square). Initial value is 256. The greater the better.
   * Resolution does not have to be a power-of-two value.
   */
  vtkSetMacro(Resolution,unsigned int);
  vtkGetMacro(Resolution,unsigned int);
  //@}

  //@{
  /**
   * Factor used to scale the maximum depth slope of a polygon (definition
   * from OpenGL 2.1 spec section 3.5.5 "Depth Offset" page 112). This is
   * used during the creation the shadow maps (not during mapping of the
   * shadow maps onto the geometry)
   * Play with this value and PolygonOffsetUnits to solve self-shadowing.
   * Valid values can be either positive or negative.
   * Initial value is 1.1f (recommended by the nVidia presentation about
   * Shadow Mapping by Cass Everitt). 3.1f works well with the regression test.
   */
  vtkSetMacro(PolygonOffsetFactor,float);
  vtkGetMacro(PolygonOffsetFactor,float);
  //@}

  //@{
  /**
   * Factor used to scale an implementation dependent constant that relates
   * to the usable resolution of the depth buffer (definition from OpenGL 2.1
   * spec section 3.5.5 "Depth Offset" page 112). This is
   * used during the creation the shadow maps (not during mapping of the
   * shadow maps onto the geometry)
   * Play with this value and PolygonOffsetFactor to solve self-shadowing.
   * Valid values can be either positive or negative.
   * Initial value is 4.0f (recommended by the nVidia presentation about
   * Shadow Mapping by Cass Everitt). 10.0f works well with the regression
   * test.
   */
  vtkSetMacro(PolygonOffsetUnits,float);
  vtkGetMacro(PolygonOffsetUnits,float);
  //@}

  /**
   * INTERNAL USE ONLY.
   * Internally used by vtkShadowMapBakerPass and vtkShadowMapPass.

   * Tell if there is at least one shadow.
   * Initial value is false.
   */
  bool GetHasShadows();

  /**
   * INTERNAL USE ONLY.
   * Internally used by vtkShadowMapBakerPass and vtkShadowMapPass.

   * Tell if the light `l' can create shadows.
   * The light has to not be a head light and to be directional or
   * positional with an angle less than 180 degrees.
   * \pre l_exists: l!=0
   */
  bool LightCreatesShadow(vtkLight *l);

  /**
   * INTERNAL USE ONLY
   * Internally used by vtkShadowMapBakerPass and vtkShadowMapPass.

   * Give access to the baked shadow maps.
   */
  vtkShadowMapBakerPassTextures *GetShadowMaps();

  /**
   * INTERNAL USE ONLY.
   * Internally used by vtkShadowMapBakerPass and vtkShadowMapPass.

   * Give access the cameras builds from the ligths.
   */
  vtkShadowMapBakerPassLightCameras *GetLightCameras();

  /**
   * INTERNAL USE ONLY.
   * Internally used by vtkShadowMapBakerPass and vtkShadowMapPass.

   * Do the shadows need to be updated?
   * Value changed by vtkShadowMapBakerPass and used by vtkShadowMapPass.
   * Initial value is true.
   */
  bool GetNeedUpdate();

  // // Description:
  // INTERNAL USE ONLY.
  // Internally used by vtkShadowMapBakerPass and vtkShadowMapPass.
  //
  // Set NeedUpate to false. Called by vtkShadowMapPass.
  void SetUpToDate();

 protected:
  /**
   * Default constructor. DelegatetPass is set to NULL.
   */
  vtkShadowMapBakerPass();

  /**
   * Destructor.
   */
  ~vtkShadowMapBakerPass() VTK_OVERRIDE;

  /**
   * Helper method to compute the mNearest point in a given direction.
   * To be called several times, with initialized = false the first time.
   * v: point
   * pt: origin of the direction
   * dir: direction
   */
  void PointNearFar(double *v,
                    double *pt,
                    double *dir,
                    double &mNear,
                    double &mFar,
                    bool initialized);

  /**
   * Compute the min/max of the projection of a box in a given direction.
   * bb: bounding box
   * pt: origin of the direction
   * dir: direction
   */
  void BoxNearFar(double *bb,
                  double *pt,
                  double *dir,
                  double &mNear,
                  double &mFar);

  /**
   * Build a camera from spot light parameters.
   * \pre light_exists: light!=0
   * \pre lcamera_exists: lcamera!=0
   */
  void BuildCameraLight(vtkLight *light,
                        double *boundingBox,
                        vtkCamera *lcamera);

  /**
   * Check if shadow mapping is supported by the current OpenGL context.
   * \pre w_exists: w!=0
   */
  void CheckSupport(vtkOpenGLRenderWindow *w);

  vtkRenderPass *OpaquePass;

  vtkRenderPass *CompositeZPass;

  unsigned int Resolution;

  float PolygonOffsetFactor;
  float PolygonOffsetUnits;

  bool HasShadows;

  /**
   * Graphics resources.
   */
  vtkFrameBufferObject *FrameBufferObject;

  vtkShadowMapBakerPassTextures *ShadowMaps;
  vtkShadowMapBakerPassLightCameras *LightCameras;


  vtkTimeStamp LastRenderTime;
  bool NeedUpdate;

private:
  vtkShadowMapBakerPass(const vtkShadowMapBakerPass&) VTK_DELETE_FUNCTION;
  void operator=(const vtkShadowMapBakerPass&) VTK_DELETE_FUNCTION;
};

#endif
