PolyDataCellNormals
VTKExamples/Cxx/PolyData/PolyDataCellNormals
Description
This example shows how to add normals to vertices. This is identical to adding normals to any type of cells. The only difference from [Normals to/from a Polydata]]([Add/Get) is
are changed to
and
Code
PolyDataCellNormals.cxx
#include <vtkCellData.h>
#include <vtkCellArray.h>
#include <vtkDoubleArray.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPointData.h>
#include <vtkSmartPointer.h>
int main(int, char *[])
{
///////// Set Point Normals ///////////
//Setup point coordinates
double x[3] = {1.0, 0.0, 0.0};
double y[3] = {0.0, 0.0, 1.0};
double z[3] = {0.0, 0.0, 0.0};
//create 3 points and add a vertex at each point
vtkSmartPointer<vtkPoints> points =
vtkSmartPointer<vtkPoints>::New();
vtkSmartPointer<vtkCellArray> vertices =
vtkSmartPointer<vtkCellArray>::New();
for ( unsigned int i = 0; i < 3; ++i )
{
//Declare a variable to store the index of the point that gets added. This behaves just like an unsigned int.
vtkIdType pid[1];
//Add a point to the polydata and save its index, which we will use to create the vertex on that point.
pid[0] = points->InsertNextPoint ( x[i], y[i], z[i] );
//create a vertex cell on the point that was just added.
vertices->InsertNextCell ( 1,pid );
}
//add the points and vertices to a polydata
vtkSmartPointer<vtkPolyData> polydata =
vtkSmartPointer<vtkPolyData>::New();
polydata->SetPoints(points);
polydata->SetVerts(vertices);
//set vertex (cell) normals
vtkSmartPointer<vtkDoubleArray> normalsArray =
vtkSmartPointer<vtkDoubleArray>::New();
normalsArray->SetNumberOfComponents(3); //3d normals (ie x,y,z)
normalsArray->SetNumberOfTuples(polydata->GetNumberOfPoints());
//construct the normal vectors
double cN1[3] = {1.0, 0.0, 0.0};
double cN2[3] = {0.0, 1.0, 0.0};
double cN3[3] = {0.0, 0.0, 1.0};
//add the data to the normals array
normalsArray->SetTuple(0, cN1) ;
normalsArray->SetTuple(1, cN2) ;
normalsArray->SetTuple(2, cN3) ;
//add the normals to the cells in the polydata
polydata->GetCellData()->SetNormals(normalsArray);
///////// Get cell normals ///////////
vtkSmartPointer<vtkDoubleArray> cellNormalsRetrieved =
vtkDoubleArray::SafeDownCast(polydata->GetCellData()->GetNormals());
if(cellNormalsRetrieved)
{
cout << "There are " << cellNormalsRetrieved->GetNumberOfTuples() << " cell normals." << endl;
for(vtkIdType i = 0; i < cellNormalsRetrieved->GetNumberOfTuples(); i++)
{
double cN[3];
cellNormalsRetrieved->GetTuple(i, cN);
cout << "Cell normal " << i << ": " << cN[0] << " " << cN[1] << " " << cN[2] << endl;
}
}
else
{
cout << "No cell normals." << endl;
}
return EXIT_SUCCESS;
}
CMakeLists.txt
cmake_minimum_required(VERSION 2.8)
PROJECT(PolyDataCellNormals)
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})
add_executable(PolyDataCellNormals MACOSX_BUNDLE PolyDataCellNormals.cxx)
target_link_libraries(PolyDataCellNormals ${VTK_LIBRARIES})
Download and Build PolyDataCellNormals
Click here to download PolyDataCellNormals and its CMakeLists.txt file. Once the tarball PolyDataCellNormals.tar has been downloaded and extracted,
cd PolyDataCellNormals/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:
./PolyDataCellNormals
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.