# Are the shift parameters affected by the scale parameter in the Similarity3DTransform

**URL:** <https://discourse.itk.org/t/are-the-shift-parameters-affected-by-the-scale-parameter-in-the-similarity3dtransform/3213>\
**Category:** Algorithms\
**Tags:** simpleitk\
**Created:** [June 20, 2020, 11:58am UTC](https://discourse.itk.org/t/are-the-shift-parameters-affected-by-the-scale-parameter-in-the-similarity3dtransform/3213 "2020-06-20T11:58:50Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Luis\_Carlos\_Carneiro](https://discourse.itk.org/user_avatar/discourse.itk.org/luis_carlos_carneiro/32/1486_2.png) [@Luis\_Carlos\_Carneiro](https://discourse.itk.org/u/Luis_Carlos_Carneiro)\
**Post date:** [June 20, 2020, 11:58am UTC](https://discourse.itk.org/t/are-the-shift-parameters-affected-by-the-scale-parameter-in-the-similarity3dtransform/3213/1 "2020-06-20T11:58:50Z")

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Dear All,

I am using the Similarity3DTransform in SimpleITK. I have a doubt. After I get the transform, the parameters concerning the shift are with the dimensions of the .mhd file or the new ones affected by the scaling of the transform?

Thanks,

Luis Gonçalves

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**Author:** ![dzenanz](https://discourse.itk.org/user_avatar/discourse.itk.org/dzenanz/32/1093_2.png) [@dzenanz](https://discourse.itk.org/u/dzenanz)\
**Post date:** [June 20, 2020, 1:08pm UTC](https://discourse.itk.org/t/are-the-shift-parameters-affected-by-the-scale-parameter-in-the-similarity3dtransform/3213/2 "2020-06-20T13:08:19Z")

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Scaling/rotation/shear are usually applied before translation.

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**Author:** ![Luis\_Carlos\_Carneiro](https://discourse.itk.org/user_avatar/discourse.itk.org/luis_carlos_carneiro/32/1486_2.png) [@Luis\_Carlos\_Carneiro](https://discourse.itk.org/u/Luis_Carlos_Carneiro)\
**Post date:** [June 21, 2020, 1:05pm UTC](https://discourse.itk.org/t/are-the-shift-parameters-affected-by-the-scale-parameter-in-the-similarity3dtransform/3213/3 "2020-06-21T13:05:21Z")

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But, for computation of the number of pixels to shift must I divide the translation parameters by “Dimensions” or “Dimensions\*Scaling”?

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**Author:** ![dzenanz](https://discourse.itk.org/user_avatar/discourse.itk.org/dzenanz/32/1093_2.png) [@dzenanz](https://discourse.itk.org/u/dzenanz)\
**Post date:** [June 21, 2020, 2:13pm UTC](https://discourse.itk.org/t/are-the-shift-parameters-affected-by-the-scale-parameter-in-the-similarity3dtransform/3213/4 "2020-06-21T14:13:13Z")

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Probably just “Dimensions”, but it is usually easier to try then to figure it out from the documentation. And you might not be thinking in terms of [physical space](https://itk.org/ITKSoftwareGuide/html/Book1/ITKSoftwareGuide-Book1ch4.html#x45-500004.1).