# Question about coordinate system transformations

**URL:** https://discourse.vtk.org/t/question-about-coordinate-system-transformations/9158
**Category:** Web
**Created:** [August 16, 2022, 5:37pm UTC](https://discourse.vtk.org/t/question-about-coordinate-system-transformations/9158 "2022-08-16T17:37:13Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![gzt036](https://discourse.vtk.org/user_avatar/discourse.vtk.org/gzt036/32/5960_2.png) [@gzt036](https://discourse.vtk.org/u/gzt036)
#### Post date: [August 16, 2022, 5:37pm UTC](https://discourse.vtk.org/t/question-about-coordinate-system-transformations/9158/1 "2022-08-16T17:37:14Z")

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What is the standard way to transform from the Screen coordinate (x,y) to world coordinate World(x,y,z) and from world coordinate to a prop3D’s local coordinate Local(x,y,z)? and how to do the reverse transformation? Thanks!

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### Author: ![Forrest](https://discourse.vtk.org/user_avatar/discourse.vtk.org/forrest/32/300_2.png) [@Forrest](https://discourse.vtk.org/u/Forrest)
#### Post date: [August 16, 2022, 7:35pm UTC](https://discourse.vtk.org/t/question-about-coordinate-system-transformations/9158/2 "2022-08-16T19:35:57Z")

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Screen to world coordinates: there is `computeDisplayToWorld` and `computeWorldToDisplay` as part of the [InteractorObserver exports](https://github.com/Kitware/vtk-js/blob/master/Sources/Rendering/Core/InteractorObserver/index.js#L30).

An actor’s transform matrix can be obtained via `prop.getMatrix()`. The inverse should take you to local coordinates.