# VectorDot

Repository source: 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 (-1,1).

Question

### Code¶

VectorDot.cxx

#include <vtkFloatArray.h>
#include <vtkNew.h>
#include <vtkPointData.h>
#include <vtkPoints.h>
#include <vtkPolyData.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
vtkNew<vtkPoints> points;
points->InsertNextPoint(0, 0, 0);
points->InsertNextPoint(1, 0, 0);
points->InsertNextPoint(2, 0, 0);

vtkNew<vtkPolyData> polydata;
polydata->SetPoints(points);

vtkNew<vtkFloatArray> normals;
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);

vtkNew<vtkFloatArray> vectors;
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.
vtkNew<vtkVectorDot> vectorDot;
vectorDot->SetInputData(polydata);
vectorDot->Update();

// Get the results.
auto scalars = dynamic_cast<vtkFloatArray*>(
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 3.12 FATAL_ERROR)

project(VectorDot)

find_package(VTK COMPONENTS
CommonCore
CommonDataModel
FiltersCore
)

if (NOT VTK_FOUND)
message(FATAL_ERROR "VectorDot: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
target_link_libraries(VectorDot PRIVATE ${VTK_LIBRARIES} ) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS VectorDot MODULES${VTK_LIBRARIES}
)


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

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.