4

I have 2 matrix:

#for example
rotation = matrix([[ 0.61782155,  0.78631834,  0.        ],
            [ 0.78631834, -0.61782155,  0.        ],
            [ 0.        ,  0.        , -1.        ]])
translation = matrix([[-0.33657291],
            [ 1.04497454],
            [ 0.        ]])
vtkinputpath = "/hello/world/vtkfile.vtk"
vtkoutputpath = "/hello/world/vtkrotatedfile.vtk"
interpolation = "linear"

I have a vtk file which contains 3D image and I want to create a function in python to rotate/translate with interpolation it.

import vtk

def rotate(vtkinputpath, vtkoutputpath, rotation, translation, interpolation):
  ...

I'm trying to take inspiration from the transformJ plugin sources (see here to understand how it works)

I wanted to use vtk.vtkTransform but I don't really understand how it works: these examples are not close enough of what I want to do. This is what I did with that:

reader = vtk.vtkXMLImageDataReader()
reader.SetFileName(vtkinputpath)
reader.Update()
transform = reader.vtkTransform()
transform.RotateX(rotation[0])
transform.RotateY(rotation[1])
transform.RotateZ(rotation[2])
transform.Translate(translation[0], translation[1], translation[2])
#and I don't know how I can choose the parameter of the interpolation

But that cannot work... I saw here that the function RotateWXYZ() exists:

# create a transform that rotates the cone
transform = vtk.vtkTransform()
transform.RotateWXYZ(45,0,1,0)
transformFilter=vtk.vtkTransformPolyDataFilter()
transformFilter.SetTransform(transform)
transformFilter.SetInputConnection(source.GetOutputPort())
transformFilter.Update()

But I don't understand what the lines do. My main problem is that I cannot find the vtk documentation for Python...

Can you advise me a documentation website for vtk in Python ? Or can you explain me at least how vtktransform (rotateWXYZ()) work ? Please, I'm totally lost, nothing works.

EaudeRoche
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1 Answers1

3

I'm not sure there is specific Python documentation, but this can be useful to understand how RotateWXYZ works: http://www.vtk.org/doc/nightly/html/classvtkTransform.html#a9a6bcc6b824fb0a9ee3a9048aa6b262c

To create the transform you want you can combine rotation and translation matrices into a 4x4 matrix, to do this we put the rotation matrix in columns and rows 0,1 and 2, we put the translation vector in the right column, the bottom row is 0,0,0,1. Here's some more info about this. For example:

0.61782155   0.78631834  0      -0.33657291
0.78631834  -0.61782155  0       1.04497454
0            0          -1       0
0            0           0       1

Then you can directly set the matrix to vtkTransform using SetMatrix:

matrix = [0.61782155,0.78631834,0,-0.33657291,0.78631834,-0.61782155,0,1.04497454,0,0,-1,0,0,0,0,1]
transform.SetMatrix(matrix)

EDIT: Edited to complete the values in the matrix variable.

Alberto F. Pena
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  • I read the description of your link, thanks. But I'm not sure that I understood well the SetMatrix function... I'm trying to convert my rotation matrix to an angle and a vector (<=> the axis of the rotation). I tried to understand the sources of vtkTransform (http://www.vtk.org/doc/nightly/html/vtkTransform_8h_source.html) but I'm not sure that I understand what it does... So thanks a lot, I'll update my question if my attempt doesn't work too. – EaudeRoche May 27 '16 at 15:01
  • I edited the answer to show the correct values in the matrix. If you set that matrix to the transform using [SetMatrix](http://www.vtk.org/doc/nightly/html/classvtkTransform.html#ad58b847446d791391e32441b98eff151) you get a transform that applies the rotation and translation given in your example. After that you can use vtkImageReslice to apply the transform to a image. I hope this helps you a little more. – Alberto F. Pena May 27 '16 at 16:38