ITK  5.3.0
Insight Toolkit
Examples/DataRepresentation/Mesh/PointSetWithVectors.cxx
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// 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 the 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
//
// \begin{floatingfigure}[rlp]{6cm}
// \centering
// \includegraphics[width=4cm]{PointSetWithVectors}
// \caption[PointSet with Vectors as PixelType]{Vectors as
// PixelType.\label{fig:PointSetWithVectors}}
// \end{floatingfigure}
//
// The \code{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.\newline
//
//
// \index{itk::Vector!itk::PointSet}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
constexpr unsigned int Dimension = 3;
using PixelType = itk::Vector<float, Dimension>;
// 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
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;
unsigned int pointId = 0;
constexpr double radius = 300.0;
for (unsigned int i = 0; i < 360; i++)
{
const double angle = i * itk::Math::pi / 180.0;
point[0] = radius * std::sin(angle);
point[1] = radius * std::cos(angle);
point[2] = 1.0; // flat on the Z plane
tangent[0] = std::cos(angle);
tangent[1] = -std::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
using PointDataIterator = PointSetType::PointDataContainer::ConstIterator;
PointDataIterator pixelIterator = pointSet->GetPointData()->Begin();
PointDataIterator pixelEnd = pointSet->GetPointData()->End();
using PointIterator = PointSetType::PointsContainer::Iterator;
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 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 EXIT_SUCCESS;
}
itk::PointSet
A superclass of the N-dimensional mesh structure; supports point (geometric coordinate and attribute)...
Definition: itkPointSet.h:82
itk::GTest::TypedefsAndConstructors::Dimension2::PointType
ImageBaseType::PointType PointType
Definition: itkGTestTypedefsAndConstructors.h:51
itk::Vector
A templated class holding a n-Dimensional vector.
Definition: itkVector.h:62
itkVector.h
itkPointSet.h
itk::Math::pi
static constexpr double pi
Definition: itkMath.h:64
itk::GTest::TypedefsAndConstructors::Dimension2::Dimension
constexpr unsigned int Dimension
Definition: itkGTestTypedefsAndConstructors.h:44