# Invisible wall limiting segmentation

**URL:** <https://discourse.slicer.org/t/invisible-wall-limiting-segmentation/46973>\
**Category:** Support\
**Tags:** segmentation\
**Created:** [May 8, 2026, 6:05pm UTC](https://discourse.slicer.org/t/invisible-wall-limiting-segmentation/46973 "2026-05-08T18:05:36Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![FabricioFO](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/fabriciofo/32/82005_2.png) [@FabricioFO](https://discourse.slicer.org/u/FabricioFO)\
**Post date:** [May 8, 2026, 6:05pm UTC](https://discourse.slicer.org/t/invisible-wall-limiting-segmentation/46973/1 "2026-05-08T18:05:36Z")

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```auto
Example

```

Hello, everyone.

I’m facing the same problem as in the video: I try to segment a specific region and it doesn’t work, it seems like there’s an invisible wall preventing me from segmenting that region even with the threshold enabled and capturing the region’s density. When I go to Source Volume and select the same volume I’m using, this invisible barrier disappears, but everything becomes very heavy, making it difficult to work. Has this happened to you before? Were you able to fix it? There is an example in the link!

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**Author:** ![muratmaga](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/muratmaga/32/3622_2.png) [@muratmaga](https://discourse.slicer.org/u/muratmaga)\
**Post date:** [May 8, 2026, 8:00pm UTC](https://discourse.slicer.org/t/invisible-wall-limiting-segmentation/46973/2 "2026-05-08T20:00:31Z")

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You might have forgotten to attach video or the screenshot that explains your problem.

From your description this sounds like geometry mismatch between the source volume and the segmentation object. Right click on your volume, choose Segment this, and then retry, and see if it fixes.

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<div class="post-metadata">

**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:** [May 10, 2026, 11:52pm UTC](https://discourse.slicer.org/t/invisible-wall-limiting-segmentation/46973/3 "2026-05-10T23:52:49Z")

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See some more details in the [Segmentation FAQ](https://slicer.readthedocs.io/en/latest/user_guide/modules/segmenteditor.html#cannot-paint-outside-some-boundaries).

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<div class="post-metadata">

**Author:** ![FabricioFO](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/fabriciofo/32/82005_2.png) [@FabricioFO](https://discourse.slicer.org/u/FabricioFO)\
**Post date:** [June 3, 2026, 2:46pm UTC](https://discourse.slicer.org/t/invisible-wall-limiting-segmentation/46973/4 "2026-06-03T14:46:44Z")

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> [@FabricioFO](#):
>
> `Example`

Sorry, here it’s the video [https://drive.google.com/file/d/1FeHXU00pTNqofsARQXDOdh7w6ihN5ti\_/view?usp=sharing](https://drive.google.com/file/d/1FeHXU00pTNqofsARQXDOdh7w6ihN5ti_/view?usp=sharing)

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<div class="post-metadata">

**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:** [June 3, 2026, 8:46pm UTC](https://discourse.slicer.org/t/invisible-wall-limiting-segmentation/46973/5 "2026-06-03T20:46:07Z")

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It looks like the segmentation geometry is set to a smaller size than the volume (for example, you may have created the segmentation when a smaller volume was displayed as background volume). You can fix it by [clicking on the Specify geometry button](https://slicer.readthedocs.io/en/latest/user_guide/modules/segmenteditor.html#cannot-paint-outside-some-boundaries) and set the geometry based on the volume that you are segmenting now.