VTK/Examples/Cxx/PolyData/Casting

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This example creates a polydata object with 3 points and attaches a distance value to each point. To retrieve the array from the polydata, we have to use a SafeDownCast to the type that we want. This is necessary because to keep things as general as possible the polydata will return an abstract array class.

Casting.cxx

#include <vtkSmartPointer.h>
#include <vtkDoubleArray.h>
#include <vtkIntArray.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPointData.h>
 
int main(int, char *[])
{
  // Create points
  vtkSmartPointer<vtkPoints> points =
    vtkSmartPointer<vtkPoints>::New();
 
  unsigned int numberOfPoints = 3;
  points->InsertNextPoint ( 0.0, 0.0, 0.0 );
  points->InsertNextPoint ( 1.0, 0.0, 0.0 );
  points->InsertNextPoint ( 0.0, 1.0, 0.0 );
 
  // Add the points to a polydata
  vtkSmartPointer<vtkPolyData> polydata =
    vtkSmartPointer<vtkPolyData>::New();
  polydata->SetPoints ( points );
 
  // Add distances to each point
  vtkSmartPointer<vtkDoubleArray> distances =
    vtkSmartPointer<vtkDoubleArray>::New();
  distances->SetNumberOfComponents(1);
  distances->SetName("Distances");
 
  distances->InsertNextValue(1.1);
  distances->InsertNextValue(2.2);
  distances->InsertNextValue(3.3);
 
  polydata->GetPointData()->AddArray ( distances );
 
  // Get the distances from the polydata
  vtkDoubleArray* array = vtkDoubleArray::SafeDownCast ( polydata->GetPointData()->GetArray ( "Distances" ) );
 
  if ( array )
    {
    for ( unsigned int i = 0; i < numberOfPoints; i++ )
      {
      double dist;
      dist = array->GetValue ( i );
      std::cout << "Distance: " << dist << std::endl;
      }
    }
 
  // Cast the double distances to ints
  vtkDoubleArray* doubleDistances = vtkDoubleArray::SafeDownCast(
                   polydata->GetPointData()->GetArray("Distances"));
  vtkIntArray* intDistances = vtkIntArray::SafeDownCast(doubleDistances);
 
  if(intDistances)
    {
    for(unsigned int i = 0; i < numberOfPoints; i++)
      {
      int dist;
      dist = intDistances->GetValue ( i );
      std::cout << "Distance: " << dist << std::endl;
      }
    }
  else
    {
    std::cout << "invalid cast." << std::endl;
    }
 
  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.6)
PROJECT(Casting)
 
FIND_PACKAGE(VTK REQUIRED)
INCLUDE(${VTK_USE_FILE})
 
ADD_EXECUTABLE(Casting Casting.cxx)
TARGET_LINK_LIBRARIES(Casting vtkHybrid)
Retrieved from "http://batchmake.org/Wiki/VTK/Examples/Cxx/PolyData/Casting"
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