# How to transform coordinate between world coordinate system and volume(data) coordinate system

**URL:** https://discourse.vtk.org/t/how-to-transform-coordinate-between-world-coordinate-system-and-volume-data-coordinate-system/3419
**Category:** Support
**Created:** [May 29, 2020, 12:43pm UTC](https://discourse.vtk.org/t/how-to-transform-coordinate-between-world-coordinate-system-and-volume-data-coordinate-system/3419 "2020-05-29T12:43:41Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![jiangyuanzhu](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jiangyuanzhu](https://discourse.vtk.org/u/jiangyuanzhu)
#### Post date: [May 29, 2020, 12:43pm UTC](https://discourse.vtk.org/t/how-to-transform-coordinate-between-world-coordinate-system-and-volume-data-coordinate-system/3419/1 "2020-05-29T12:43:41Z")

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ear VTK,

Could you please share more information about how to transform coordinate between world coordinate system and volume(data) coordinate system?

In my project, a NIFTI volume data is loaded.And I displayed this volume based on “vtkGPUVolumeRayCastMapper”.

In this case, I am not quite clear about the difference between world coordinate and volume coordinate.  
When I picked a point based on “vtkPropPicker”, I think this point belongs to world coordinate.  
How can I transform it to volume space?

Thank you so much for your help!  
Jiangyuan Zhu