# How do I take linear measurements on 3D Volume rendered surface?

**URL:** <https://discourse.slicer.org/t/how-do-i-take-linear-measurements-on-3d-volume-rendered-surface/26230>\
**Category:** Support\
**Created:** [November 14, 2022, 2:27pm UTC](https://discourse.slicer.org/t/how-do-i-take-linear-measurements-on-3d-volume-rendered-surface/26230 "2022-11-14T14:27:18Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![KSL](https://avatars.discourse-cdn.com/v4/letter/k/82dd89/32.png) [@KSL](https://discourse.slicer.org/u/KSL)\
**Post date:** [November 14, 2022, 2:27pm UTC](https://discourse.slicer.org/t/how-do-i-take-linear-measurements-on-3d-volume-rendered-surface/26230/1 "2022-11-14T14:27:18Z")

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I have tried taking measurements on the skull after volume rendering as done from the tutorial [New "Surface cut" and "Mask volume" tools for 3D Slicer segment editor - YouTube](https://youtu.be/xZwyW6SaoM4) but my control points cannot be fixed onto the bone surface.

Operating system: windows 11  
Slicer version: 5.0.3  
Expected behavior: to be able to take linear measurements with the control points fixed onto the bone surface  
Actual behavior: the control points (the lines) get scattered in the 3D space even after locking the control points

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [November 15, 2022, 12:15pm UTC](https://discourse.slicer.org/t/how-do-i-take-linear-measurements-on-3d-volume-rendered-surface/26230/2 "2022-11-15T12:15:05Z")

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Is “Snap to visible surface” option is selected Markups module → Display → Advanced → 3D display → Placement mode?

What volume rendering technique do you use (CPU, GPU, multi-volume)?

Did the volume-rendered surface appear opaque or semi-transparent? Could you provide a screenshot?

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**Author:** ![KSL](https://avatars.discourse-cdn.com/v4/letter/k/82dd89/32.png) [@KSL](https://discourse.slicer.org/u/KSL)\
**Post date:** [November 16, 2022, 5:27am UTC](https://discourse.slicer.org/t/how-do-i-take-linear-measurements-on-3d-volume-rendered-surface/26230/3 "2022-11-16T05:27:30Z")

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Thank you, Sir

My problem gets resolved after following your instructions.  
Placement mode (Snap to Visible surface)

Volume rendering technique (GPU)