DataRepresentation/Mesh/PointSetWithVectors.cxx

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

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: PointSetWithVectors.cxx,v $
  Language:  C++
  Date:      $Date: 2005-11-19 16:31:49 $
  Version:   $Revision: 1.17 $

  Copyright (c) Insight Software Consortium. All rights reserved.
  See ITKCopyright.txt or http://www.itk.org/HTML/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 notices for more information.

=========================================================================*/
#if defined(_MSC_VER)
#pragma warning ( disable : 4786 )
#endif

//  Software Guide : BeginLatex
//
//  This example illustrates how a point set can be parameterized to manage a
//  particular pixel type. It is quite common to associate vector values with
//  points for producing geometric representations.  The following code shows
//  how vector values can be used as pixel type on the PointSet class.  The
//  \doxygen{Vector} class is used here as the pixel type. This class is
//  appropriate for representing the relative position between two points. It
//  could then be used to manage displacements, for example.
//  
//  \index{itk::PointSet!Vector pixels}
//  
//  In order to use the vector class it is necessary to include its header file
//  along with the header of the point set.
//
//  Software Guide : EndLatex 

// Software Guide : BeginCodeSnippet
#include "itkVector.h"
#include "itkPointSet.h"
// Software Guide : EndCodeSnippet


int main(int, char *[])
{
  //  Software Guide : BeginLatex
  //
  //  \itkpiccaption[PointSet with Vectors as PixelType]{Vectors as PixelType.\label{fig:PointSetWithVectors}}
  //  \parpic(6cm,4cm)[r]{\includegraphics[width=4cm]{PointSetWithVectors.eps}}
  //
  //  The Vector class is templated over the type used to represent
  //  the spatial coordinates and over the space dimension.  Since the
  //  PixelType is independent of the PointType, we are free to select any
  //  dimension for the vectors to be used as pixel type. However, for the
  //  sake of producing an interesting example, we will use vectors that 
  //  represent displacements of the points in the PointSet. Those vectors
  //  are then selected to be of the same dimension as the PointSet.
  //
  //  \index{itk::Vector!itk::PointSet}
  //
  //  Software Guide : EndLatex 

  // Software Guide : BeginCodeSnippet
  const unsigned int Dimension = 3;
  typedef itk::Vector< float, Dimension >    PixelType;
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  Then we use the PixelType (which are actually Vectors) to instantiate the
  //  PointSet type and subsequently create a PointSet object.
  //
  //  Software Guide : EndLatex 

  // Software Guide : BeginCodeSnippet
  typedef itk::PointSet< PixelType, Dimension > PointSetType;
  PointSetType::Pointer  pointSet = PointSetType::New();
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  The following code is generating a sphere and assigning vector values
  //  to the points. The components of the vectors in this example are
  //  computed to represent the tangents to the circle as shown in
  //  Figure~\ref{fig:PointSetWithVectors}.
  //
  //  \index{itk::PointSet!SetPoint()}
  //  \index{itk::PointSet!SetPointData()}
  //
  //  Software Guide : EndLatex 

  // Software Guide : BeginCodeSnippet
  PointSetType::PixelType   tangent;
  PointSetType::PointType   point;

  unsigned int pointId =  0;
  const double radius = 300.0;

  for(unsigned int i=0; i<360; i++)
    {
    const double angle = i * atan(1.0) / 45.0;
    point[0] = radius * sin( angle );
    point[1] = radius * cos( angle );
    point[2] = 1.0;   // flat on the Z plane
    tangent[0] =  cos(angle);
    tangent[1] = -sin(angle);
    tangent[2] = 0.0;  // flat on the Z plane
    pointSet->SetPoint( pointId, point );   
    pointSet->SetPointData( pointId, tangent );   
    pointId++;
    }
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  We can now visit all the points and use the vector on the pixel values to
  //  apply a displacement on the points. This is along the spirit of what a
  //  deformable model could do at each one of its iterations. 
  //
  //  \index{itk::PointSet!PointIterator}
  //  \index{itk::PointSet!GetPoints()}
  //  \index{itk::PointSet!GetPointData()}
  //
  //  Software Guide : EndLatex 


  // Software Guide : BeginCodeSnippet
  typedef  PointSetType::PointDataContainer::ConstIterator PointDataIterator;
  PointDataIterator pixelIterator = pointSet->GetPointData()->Begin();
  PointDataIterator pixelEnd      = pointSet->GetPointData()->End();

  typedef  PointSetType::PointsContainer::Iterator     PointIterator;
  PointIterator pointIterator = pointSet->GetPoints()->Begin();
  PointIterator pointEnd      = pointSet->GetPoints()->End();

  while( pixelIterator != pixelEnd  && pointIterator != pointEnd ) 
    {
    pointIterator.Value() = pointIterator.Value() + pixelIterator.Value();
    ++pixelIterator;
    ++pointIterator;
    }
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  Note that the \code{ConstIterator} was used here instead of the normal
  //  \code{Iterator} since the pixel values are only intended to be read and
  //  not modified. ITK supports const-correctness at the API level.
  //
  //  \index{ConstIterator}
  //  \index{const-correctness}
  //
  //  Software Guide : EndLatex 


  //  Software Guide : BeginLatex
  //
  //  The \doxygen{Vector} class has overloaded the \code{+} operator with
  //  the \doxygen{Point}. In other words, vectors can be added to points in
  //  order to produce new points.  This property is exploited in the center
  //  of the loop in order to update the points positions with a single
  //  statement.
  //
  //  \index{itk::PointSet!PointIterator}
  //
  //  We can finally visit all the points and print out the new values
  //
  //  Software Guide : EndLatex 

  // Software Guide : BeginCodeSnippet
  pointIterator = pointSet->GetPoints()->Begin();
  pointEnd      = pointSet->GetPoints()->End();
  while( pointIterator != pointEnd ) 
    {
    std::cout << pointIterator.Value() << std::endl;
    ++pointIterator;
    }
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  Note that \doxygen{Vector} is not the appropriate class for
  //  representing normals to surfaces and gradients of functions. This is due
  //  to the way in which vectors behave under affine transforms. ITK has a
  //  specific class for representing normals and function gradients. This is
  //  the \doxygen{CovariantVector} class.
  //
  //  Software Guide : EndLatex 

  return 0;
}

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