vtkPointInterpolator gives new arrays

I have the following function:

def interpolateToGrid( mesh: vtkPolyData, grid: vtkStructuredGrid, gridSize ):
    # Perform the interpolation
    interpolator = vtkPointInterpolator()
    gaussianKernel = vtkGaussianKernel()
    gaussianKernel.SetRadius( gridSize*15)
    interpolator.SetSourceData( mesh )
    interpolator.SetInputData( grid )
    interpolator.SetKernel( gaussianKernel )

    #output = interpolator.GetOutput()
    output = vtkStructuredGrid()
    return output

grid initially had 2 scalar arrays
The returned vtkStructuredGrid object I get from interpolator.GetOutput() has 14 more arrays
The new arrays - [stress_xx, stress_yy, stress_zz, stress_xy, stress_yz, stress_xz, vonmises, strain_xx, strain_yy, strain_zz, strain_xy, strain_yz, strain_xz, displacement] I understand these values are related to FEA
but I am not able to find the origin of these new arrays
neither in the documentation nor in the source code

Kindly help

This is solved, I didn’t understand the behaviour of interpolation functions before. Thanks