# VTK/Examples/Cxx/Math/VectorDot

< VTK‎ | Examples‎ | Cxx(Redirected from VTK/Examples/Broken/VectorDot)

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].

## 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);

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);

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;
}
```

# Please try the new VTKExamples website.

## CMakeLists.txt

```cmake_minimum_required(VERSION 2.8)

PROJECT(VectorDot)

find_package(VTK REQUIRED)
include(\${VTK_USE_FILE})

if(VTK_LIBRARIES)
else()
endif()
```

```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.