# What is the best way to visualize detector curvature in case of forward projection calculation?

**URL:** https://discourse.slicer.org/t/what-is-the-best-way-to-visualize-detector-curvature-in-case-of-forward-projection-calculation/22482
**Category:** Development
**Tags:** markups
**Created:** [March 13, 2022, 10:29am UTC](https://discourse.slicer.org/t/what-is-the-best-way-to-visualize-detector-curvature-in-case-of-forward-projection-calculation/22482 "2022-03-13T10:29:58Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![Mik](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mik](https://discourse.slicer.org/u/Mik)
#### Post date: [March 13, 2022, 10:29am UTC](https://discourse.slicer.org/t/what-is-the-best-way-to-visualize-detector-curvature-in-case-of-forward-projection-calculation/22482/1 "2022-03-13T10:29:58Z")

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I’m making a forward projection calculation using RTK.

In case of parallel geometry or a flat detector the detector surface can be visualize as a MarkupsPlaneNode.

What could you suggest in case of the detector with a radius? The scheme is [here](http://www.openrtk.org/Doxygen/DocGeo3D.html#DR). Can a grid transform be used in that case, and can it be applied to a MarkupsPlaneNode?

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### Author: ![mau\_igna\_06](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/mau_igna_06/32/9056_2.png) [@mau\_igna\_06](https://discourse.slicer.org/u/mau_igna_06)
#### Post date: [March 13, 2022, 11:58am UTC](https://discourse.slicer.org/t/what-is-the-best-way-to-visualize-detector-curvature-in-case-of-forward-projection-calculation/22482/2 "2022-03-13T11:58:25Z")

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You could create an uncapped cylinder of the corresponding size with vtkCylinderSource filter, assign its output to a modelNode and crop the model with two markupsPlanes created by code with the dynamicModeler’s tool planeCut

You can make same GUI and set up event observers to make this easy to edit if you want.

On your method the radial simmetry of the aproximated cylinder will be limited by volume spacing. In the method I described it will be limited by the resolution factor you set up on the cylinderSource.

If you want more points along the cylinder’s height you should use vtkTubeFilter instead of vtkCylinderSource

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### Author: ![Mik](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mik](https://discourse.slicer.org/u/Mik)
#### Post date: [March 13, 2022, 5:27pm UTC](https://discourse.slicer.org/t/what-is-the-best-way-to-visualize-detector-curvature-in-case-of-forward-projection-calculation/22482/3 "2022-03-13T17:27:31Z")

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Thank you!

I’ve thought about using transformation for that purpose, if detector is flat, then linear transform, if it has a radius, then grid transform or something else.

I will think about using models for that.