[vtkusers] Obtaining transformation matrix for vtkPolyData

[Eric Petersen]

Thanks David,

I've got a class setup for reading/writing STL files along with basic
manipulation.  My rotation code is below and called successive times.  I
guess the question is does VTK "remember" past transformations on a
vtkPolyData object()?  If so, what's the best way of accessing them?

def Rotate(self, alpha, beta, gamma):
        t = vtk.vtkTransform()
        t.RotateX(alpha)
        t.RotateY(beta)
        t.RotateZ(gamma)
        tf = vtk.vtkTransformPolyDataFilter()
        tf.SetInputData(self.MeshData)
        tf.SetTransform(t)
        tf.Update()
        self.MeshData.ShallowCopy(tf.GetOutput())

On Fri, Aug 18, 2017 at 8:33 AM, David E DeMarle <dave.demarle at kitware.com>
wrote:

> Howdy Eric,
>
> How are you doing the transform?
> * vtkTransformFIlter?
> * vtkActor::Transform?
> * manually changing the points in the vtkPolyData object?
>
> For either of the first two you can get the current matrix (and its
> inverse) from the transform object.
>
> hope that helps
>
>
> David E DeMarle
> Kitware, Inc.
> Principal Engineer
> 21 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-881-4909 <(518)%20881-4909>
>
> On Fri, Aug 18, 2017 at 8:11 AM, Eric Petersen <peer9802 at gmail.com> wrote:
>
>> Hello,
>>
>> I currently have a Python script where I am successively translating, and
>> rotating, a vtkPolyData object.  The script currently does not track
>> individual transforms but I would like to know the current 4x4 transform
>> matrix.  Is there any way to directly obtain this information from the
>> vtkPolyData object or am I stuck rewriting the script to track individual
>> transformations?
>>
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