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Program: Visualization Toolkit
Module: vtkViewDependentErrorMetric.h
Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
All rights reserved.
See Copyright.txt or for details.
This software is distributed WITHOUT ANY WARRANTY; without even
PURPOSE. See the above copyright notice for more information.
// .NAME vtkViewDependentErrorMetric - Objects that compute a
// screen-based error during cell tessellation.
// .SECTION Description
// 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
// .SECTION See Also
// vtkGenericCellTessellator vtkGenericSubdivisionErrorMetric
#ifndef __vtkViewDependentErrorMetric_h
#define __vtkViewDependentErrorMetric_h
#include "vtkGenericSubdivisionErrorMetric.h"
class vtkViewport;
class vtkCoordinate;
class VTK_FILTERING_EXPORT vtkViewDependentErrorMetric : public vtkGenericSubdivisionErrorMetric
// Description:
// 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();
// Description:
// Standard VTK type and error macros.
void PrintSelf(ostream& os, vtkIndent indent);
// Description:
// Return the squared screen-based geometric accurary measured in pixels.
// An accuracy less or equal to 0.25 (0.5^2) ensures that the screen-space
// interpolation of a mid-point matchs 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);
// Description:
// 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);
// Description:
// Set/Get the renderer with `renderer' on which the error metric
// is based. The error metric use the active camera of the renderer.
void SetViewport(vtkViewport *viewport);
// Description:
// 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);
// Description:
// 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);
// Description:
// 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;
vtkViewDependentErrorMetric(const vtkViewDependentErrorMetric&); // Not implemented.
void operator=(const vtkViewDependentErrorMetric&); // Not implemented.