VectorDot
VTKExamples/Cxx/Math/VectorDot
Description
Note that the filter maps the values to a scalar range. In the example, the values of the dot products are 1, .707, 0
The filter outputs 1, .414, -1
because the default scalar range that the filter maps the values to is .
Code
VectorDot.cxx
#include <vtkVersion.h>
#include <vtkSmartPointer.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkFloatArray.h>
#include <vtkPointData.h>
#include <vtkVectorDot.h>
// For compatibility with new VTK generic data arrays
#ifdef vtkGenericDataArray_h
#define InsertNextTupleValue InsertNextTypedTuple
#endif
int main(int, char *[])
{
// Generate data
vtkSmartPointer<vtkPoints> points =
vtkSmartPointer<vtkPoints>::New();
points->InsertNextPoint(0,0,0);
points->InsertNextPoint(1,0,0);
points->InsertNextPoint(2,0,0);
vtkSmartPointer<vtkPolyData> polydata =
vtkSmartPointer<vtkPolyData>::New();
polydata->SetPoints(points);
// Add normals
vtkSmartPointer<vtkFloatArray> normals =
vtkSmartPointer<vtkFloatArray>::New();
normals->SetNumberOfComponents(3);
normals->SetName("Normals");
float n0[3] = {1,0,0};
float n1[3] = {1,0,0};
float n2[3] = {1,0,0};
normals->InsertNextTupleValue(n0);
normals->InsertNextTupleValue(n1);
normals->InsertNextTupleValue(n2);
polydata->GetPointData()->SetNormals(normals);
// Add vectors
vtkSmartPointer<vtkFloatArray> vectors =
vtkSmartPointer<vtkFloatArray>::New();
vectors->SetNumberOfComponents(3);
vectors->SetName("Vectors");
float v0[3] = {1,0,0};
float v1[3] = {.707f,.707f,0};
float v2[3] = {0,1,0};
vectors->InsertNextTupleValue(v0);
vectors->InsertNextTupleValue(v1);
vectors->InsertNextTupleValue(v2);
polydata->GetPointData()->SetVectors(vectors);
// Compute the dot products between normals and vectors
vtkSmartPointer<vtkVectorDot> vectorDot =
vtkSmartPointer<vtkVectorDot>::New();
#if VTK_MAJOR_VERSION <= 5
vectorDot->SetInputConnection(polydata->GetProducerPort());
#else
vectorDot->SetInputData(polydata);
#endif
vectorDot->Update();
// Get the results
vtkFloatArray* scalars = vtkFloatArray::SafeDownCast ( vectorDot->GetOutput()->GetPointData()->GetScalars() );
// Output the results
for(vtkIdType i = 0; i < scalars->GetNumberOfTuples(); i++)
{
std::cout << "Value " << i << " : " << scalars->GetValue(i) << std::endl;
}
return EXIT_SUCCESS;
}
CMakeLists.txt
cmake_minimum_required(VERSION 2.8)
PROJECT(VectorDot)
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})
add_executable(VectorDot MACOSX_BUNDLE VectorDot.cxx)
target_link_libraries(VectorDot ${VTK_LIBRARIES})
Download and Build VectorDot
Click here to download VectorDot and its CMakeLists.txt file. Once the tarball VectorDot.tar has been downloaded and extracted,
cd VectorDot/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:
./VectorDot
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.