CODEWITHSUNDEEP
pythonnumpyvtk
Harry R.
Harry R.

Reputation: 771

vtk python icp how to get transform matrix

It seems that the answer to my question is pretty obvious, but unfortunately I could not figure it out, please help me!

I am trying to use the vtk library to obtain the icp transform in python.

I am running this code here: http://www.vtk.org/Wiki/VTK/Examples/Python/IterativeClosestPoints

and then 

print icp.GetLandmarkTransform()

The result displays the transformation matrix among other things.

... 

Elements:
->        1 4.76975e-10 0 -7.79873e-10 
->       -4.76975e-10 1 -0 1.58991e-10 
->       -0 0 1 0 
->        0 0 0 1 
Mode: RigidBody

...

How do I extract the transformation matrix in a numpy array? I just need the transform for a 2D data set. Is there a simpler way to do it?

Thank you in advance!

Upvotes: 3

Views: 2749

Answers (3)

Lucas Chavez
Lucas Chavez

Reputation: 91

Just a helper function that I use to do the same thing. 

def vtkmatrix_to_numpy(matrix):
    """
    Copies the elements of a vtkMatrix4x4 into a numpy array.

    :param matrix: The matrix to be copied into an array.
    :type matrix: vtk.vtkMatrix4x4
    :rtype: numpy.ndarray
    """
    m = np.ones((4, 4))
    for i in range(4):
        for j in range(4):
            m[i, j] = matrix.GetElement(i, j)
    return m

Upvotes: 2

RafaelLopes
RafaelLopes

Reputation: 473

In general vtk matrix can be extracted as python lists:

temp = [0] * 16 #the matrix is 4x4
vtk_matrix.DeepCopy(temp, vtk_matrix)

Upvotes: 3

Harry R.
Harry R.

Reputation: 771

After asking for the help of a friend he provided me with the answer. Just posting in case someone needs it:

for i in range(3):
   for j in range(4):
       print icp.GetLandmarkTransform().GetMatrix().GetElement(i, j),
   print
print

Upvotes: 4

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