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

  Program:   Visualization Toolkit
  Module:    vtkViewDependentErrorMetric.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   vtkViewDependentErrorMetric
 * @brief   Objects that compute a
 * screen-based error during cell tessellation.
 *
 *
 * It is a concrete error metric, based on a geometric criterium in
 * the screen space: the variation of the projected edge from a projected
 * straight line
 *
 * @sa
 * vtkGenericCellTessellator vtkGenericSubdivisionErrorMetric
 */

#ifndef vtkViewDependentErrorMetric_h
#define vtkViewDependentErrorMetric_h

#include "vtkGenericSubdivisionErrorMetric.h"
#include "vtkRenderingCoreModule.h" // For export macro

class vtkViewport;
class vtkCoordinate;

class VTKRENDERINGCORE_EXPORT vtkViewDependentErrorMetric : public vtkGenericSubdivisionErrorMetric
{
public:
  /**
   * Construct the error metric with a default squared screen-based geometric
   * accuracy measured in pixels equal to 0.25 (0.5^2).
   */
  static vtkViewDependentErrorMetric* New();

  ///@{
  /**
   * Standard VTK type and error macros.
   */
  vtkTypeMacro(vtkViewDependentErrorMetric, vtkGenericSubdivisionErrorMetric);
  void PrintSelf(ostream& os, vtkIndent indent) override;
  ///@}

  ///@{
  /**
   * Return the squared screen-based geometric accuracy measured in pixels.
   * An accuracy less or equal to 0.25 (0.5^2) ensures that the screen-space
   * interpolation of a mid-point matches exactly with the projection of the
   * mid-point (a value less than 1 but greater than 0.25 is not enough,
   * because of 8-neighbors). Maybe it is useful for lower accuracy in case of
   * anti-aliasing?
   * \post positive_result: result>0
   */
  vtkGetMacro(PixelTolerance, double);
  ///@}

  /**
   * Set the squared screen-based geometric accuracy measured in pixels.
   * Subdivision will be required if the square distance between the projection
   * of the real point and the straight line passing through the projection
   * of the vertices of the edge is greater than `value'.
   * For instance, 0.25 will give better result than 1.
   * \pre positive_value: value>0
   */
  void SetPixelTolerance(double value);

  ///@{
  /**
   * Set/Get the renderer with `renderer' on which the error metric
   * is based. The error metric use the active camera of the renderer.
   */
  vtkGetObjectMacro(Viewport, vtkViewport);
  void SetViewport(vtkViewport* viewport);
  ///@}

  /**
   * Does the edge need to be subdivided according to the distance between
   * the line passing through its endpoints in screen space and the projection
   * of its mid point?
   * The edge is defined by its `leftPoint' and its `rightPoint'.
   * `leftPoint', `midPoint' and `rightPoint' have to be initialized before
   * calling RequiresEdgeSubdivision().
   * Their format is global coordinates, parametric coordinates and
   * point centered attributes: xyx rst abc de...
   * `alpha' is the normalized abscissa of the midpoint along the edge.
   * (close to 0 means close to the left point, close to 1 means close to the
   * right point)
   * \pre leftPoint_exists: leftPoint!=0
   * \pre midPoint_exists: midPoint!=0
   * \pre rightPoint_exists: rightPoint!=0
   * \pre clamped_alpha: alpha>0 && alpha<1
   * \pre valid_size: sizeof(leftPoint)=sizeof(midPoint)=sizeof(rightPoint)
   * =GetAttributeCollection()->GetNumberOfPointCenteredComponents()+6
   */
  int RequiresEdgeSubdivision(
    double* leftPoint, double* midPoint, double* rightPoint, double alpha) override;

  /**
   * Return the error at the mid-point. The type of error depends on the state
   * of the concrete error metric. For instance, it can return an absolute
   * or relative error metric.
   * See RequiresEdgeSubdivision() for a description of the arguments.
   * \pre leftPoint_exists: leftPoint!=0
   * \pre midPoint_exists: midPoint!=0
   * \pre rightPoint_exists: rightPoint!=0
   * \pre clamped_alpha: alpha>0 && alpha<1
   * \pre valid_size: sizeof(leftPoint)=sizeof(midPoint)=sizeof(rightPoint)
   * =GetAttributeCollection()->GetNumberOfPointCenteredComponents()+6
   * \post positive_result: result>=0
   */
  double GetError(double* leftPoint, double* midPoint, double* rightPoint, double alpha) override;

protected:
  vtkViewDependentErrorMetric();
  ~vtkViewDependentErrorMetric() override;

  /**
   * Square distance between a straight line (defined by points x and y)
   * and a point z. Property: if x and y are equal, the line is a point and
   * the result is the square distance between points x and z.
   */
  double Distance2LinePoint(double x[2], double y[2], double z[2]);

  double PixelTolerance;
  vtkViewport* Viewport;
  // used to get display coordinates from world coordinates
  vtkCoordinate* Coordinate;

private:
  vtkViewDependentErrorMetric(const vtkViewDependentErrorMetric&) = delete;
  void operator=(const vtkViewDependentErrorMetric&) = delete;
};

#endif