Numpy array for vtk table

Question

I have the following problem. I have a numpy array like this:

arr = np.array([[   1. ,   1. ,   4.  ,  3.  ,  6. ,  12.  , -1.   , 1.],
 [   1. ,   2.  ,  2.,    2.,   10. ,   6. ,  -2. ,   2.],
 [   1. ,   2. ,   3. ,   4.  ,  4. ,  11. ,  -2.  ,  3.],
 [   1.  ,  2. ,   3. ,   6.,    8.   , 9.  ,  1. ,   4.],
 [   1.  ,  2. ,   6. ,   7.  ,  4.,   14.  ,  1. ,   5.],
 [   1.  ,  2. ,   7. ,   4. ,   2. ,  17. ,  -0.  ,  6.],
 [   1.  ,  3.  ,  2. ,   6. ,   7.  ,  3. ,  -1. ,   7.],
 [   1.  ,  3.  ,  4.  ,  1.  ,  3. ,  14. ,   0. ,   8.],
 [   1.  ,  3.  ,  5.  ,  5.   , 1. ,  16. ,  -1.  ,  9.],
 [   1.  ,  3.  ,  6. ,   2. ,   9. ,  19.  ,  1. ,  10.],
 [   1.  ,  4.  ,  3.  ,  1. ,   1.  ,  7. ,  -1.  , 11.],
 [   1.  ,  4.  ,  4. ,   5. ,   9. ,  10.  ,  2. ,  12.],
 [   1.  ,  4. ,   5.  ,  3. ,   6. ,  18. ,   0.  , 13.],
 [   1.  ,  4. ,   6.  ,  6. ,   5. ,   2. ,  -1. ,  14.],
 [   1.  ,  5. ,   1. ,   4. ,   3. ,   5. ,   1.  , 15.],
 [   2.  ,  1.  ,  2.  ,  7. ,   2. ,  19.  , -1. ,  16.],
 [   2.  ,  1.  ,  3. ,   2. ,   3. ,  16. ,  -2.  , 17.]])

Now I want to convert it to a vtk table. Is it possible?

Yours faithfully!

Answer 1

I think this can be done using the following method:

# create the vtkTable object
tab = vtk.vtkTable()

# create a vtkDataArray with arr values
vtkarr = vtk.vtkDoubleArray()
vtkarr.SetNumberOfComponents(arr.shape[1])
vtkarr.SetNumberOfTuples(arr.shape[0])
vtkarr.SetVoidArray(arr, arr.size, 0)

# finally assign the values to the vtkTable
tab.GetRowData().AddArray(vtkarr)

I tried to avoid unnecessary copies of the values ​​because of which I used SetVoidArray(). Thus, basically, the first argument is the array itself, the second is the total number of elements in the array, and the latter indicates whether you want the object to vtkTablerelease raw data or not (in which case it will).

Answer 2

An alternative method is to use the vtk numpy_support module:

import numpy as np
import vtk
from vtk.util import numpy_support

arr = np.array([[ ... ]])

vtkarr = numpy_support.numpy_to_vtk( arr, deep=True, array_type=vtk.VTK_DOUBLE )

# create the vtkTable object
tab = vtk.vtkTable()
tab.GetRowData().AddArray(vtkarr)

. , numpy_to_vtk, , SetVoidArray().

---

, , , arr.ravel(), vtkArray numpy_to_vtk, "" , vtkArray.SetNumberOfComponents():

    # arr is a 3xNxNxN array 

    # Make sure the dimension which you want to make up the tuples is at the end.
    # In our case, dimension 0 (the 3) is what we want to be in each tuple,
    # so we move it to the end:
    arr = numpy.transpose( arr, (1,2,3,0) )
    # Convert the array to vtk. ravel() flattens the array and makes sure 
    # it contiguous:
    vtkarr = numpy_support.numpy_to_vtk( arr.ravel(), deep=True, array_type=vtk.VTK_DOUBLE )
    # "Fix" the number of components:
    vtkarr.SetNumberOfComponents( 3 )
    vtkarr.SetNumberOfTuples( N*N*N )

    vtkarr.SetName("DisplacementField")
    cellData.AddArray( vtkarr )

. .