Casting
VTKExamples/Cxx/PolyData/Casting
Description
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.
Code
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 2.8)
PROJECT(Casting)
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})
add_executable(Casting MACOSX_BUNDLE Casting.cxx)
target_link_libraries(Casting ${VTK_LIBRARIES})
Download and Build Casting
Click here to download Casting and its CMakeLists.txt file. Once the tarball Casting.tar has been downloaded and extracted,
cd Casting/build
If VTK is installed:
cmake ..
If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:
cmake -DVTK_DIR:PATH=/home/me/vtk_build ..
Build the project:
make
and run it:
./Casting
WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.