# vtkTransform::Concatenate() is very slow

**URL:** https://discourse.vtk.org/t/vtktransform-concatenate-is-very-slow/2637
**Category:** Support
**Created:** [February 17, 2020, 7:24am UTC](https://discourse.vtk.org/t/vtktransform-concatenate-is-very-slow/2637 "2020-02-17T07:24:18Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![mmm](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/m/0ea827/32.png) [@mmm](https://discourse.vtk.org/u/mmm)
#### Post date: [February 17, 2020, 7:24am UTC](https://discourse.vtk.org/t/vtktransform-concatenate-is-very-slow/2637/1 "2020-02-17T07:24:18Z")

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vtkTransform::Concatenate() gets very slow after calling it multiple times.

The situation is the following:

- I call vtkTransform::Concatenate( **anotherTransform** ) to concatenate another vtkTransform (basically applying a rotation matrix if the user clicks on a button)

- After every click the Concatenate() function take longer and longer and about after 10 clicks the call takes about 1000ms

- Now I found out that if I extract the vtkMatrix4x4 from the **anotherTransform** (the transform I concatenate) and set it to a newly created vtkTransform the speed of Concatenate() is very fast each time

Anyone has an idea what the reason for this behaviour is? Am I using the vtkTransform the wrong way or did I forget to set some flag?

I used Instruments on macOS and figured out that vtkTransform::CircuitCheck() uses a lot of computation time, but I can’t figure out why.