# Simple Filters: node selector doesn't accept Scalar Volume child nodes

**URL:** <https://discourse.slicer.org/t/simple-filters-node-selector-doesnt-accept-scalar-volume-child-nodes/22571>\
**Category:** Development\
**Created:** [March 17, 2022, 10:45pm UTC](https://discourse.slicer.org/t/simple-filters-node-selector-doesnt-accept-scalar-volume-child-nodes/22571 "2022-03-17T22:45:55Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![keri](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/keri/32/11618_2.png) [@keri](https://discourse.slicer.org/u/keri)\
**Post date:** [March 17, 2022, 10:45pm UTC](https://discourse.slicer.org/t/simple-filters-node-selector-doesnt-accept-scalar-volume-child-nodes/22571/1 "2022-03-17T22:45:55Z")

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Hi,

Is there any reasons why SimpleFilters I/O node selectors don’t accept volume nodes inherited from `vtkMRMLScalarVolumeNode` (child nodes)?

For example I just tried to set [inputSelector.showChildNodeTypes = True](https://github.com/SimpleITK/SlicerSimpleFilters/blob/92e8db0030f6f9d9ea99dd5d8d1425b6b2189a68/SimpleFilters/SimpleFilters.py#L893) and it works fine with my custom volume node, I wa able to calculate `CosImageFilter`

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [March 18, 2022, 12:55pm UTC](https://discourse.slicer.org/t/simple-filters-node-selector-doesnt-accept-scalar-volume-child-nodes/22571/2 "2022-03-18T12:55:54Z")

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This was probably done because some [subclasses](http://apidocs.slicer.org/master/classvtkMRMLScalarVolumeNode.html) wouldn’t work with SimpleITK. But since some would work and because this is sort of an advanced module anyway it might make sense to relax the requirement.

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**Author:** ![keri](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/keri/32/11618_2.png) [@keri](https://discourse.slicer.org/u/keri)\
**Post date:** [March 18, 2022, 1:04pm UTC](https://discourse.slicer.org/t/simple-filters-node-selector-doesnt-accept-scalar-volume-child-nodes/22571/3 "2022-03-18T13:04:12Z")

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Thank you, it would be good

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [March 18, 2022, 1:10pm UTC](https://discourse.slicer.org/t/simple-filters-node-selector-doesnt-accept-scalar-volume-child-nodes/22571/4 "2022-03-18T13:10:08Z")

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You could submit a PR and then if anyone sees a downside they could comment there.

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<div class="post-metadata">

**Author:** ![keri](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/keri/32/11618_2.png) [@keri](https://discourse.slicer.org/u/keri)\
**Post date:** [March 18, 2022, 2:41pm UTC](https://discourse.slicer.org/t/simple-filters-node-selector-doesnt-accept-scalar-volume-child-nodes/22571/5 "2022-03-18T14:41:08Z")

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Just in case the PR is [ready](https://github.com/SimpleITK/SlicerSimpleFilters/pull/24)