# Non-linear transforms not supported for volume rendering?

**URL:** <https://discourse.slicer.org/t/non-linear-transforms-not-supported-for-volume-rendering/23647>\
**Category:** Support\
**Tags:** slicerigt\
**Created:** [May 30, 2022, 9:49pm UTC](https://discourse.slicer.org/t/non-linear-transforms-not-supported-for-volume-rendering/23647 "2022-05-30T21:49:22Z")\
**Posts on this page:** 3\
**Page:** 1

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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 30, 2022, 9:49pm UTC](https://discourse.slicer.org/t/non-linear-transforms-not-supported-for-volume-rendering/23647/1 "2022-05-30T21:49:22Z")

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I am using the Fiducial Registration Wizard to make a visual. When I choose the resultant transform as warping and set to store in a transform (not linear transform), I am getting this error when I try to apply this transform to a volume rendering node.

```auto
Failed to get transformation matrix because transform is not linear

Generic Warning: In /work/Stable/Slicer-0/Libs/MRML/Core/vtkMRMLTransformNode.cxx, line 929
vtkMRMLTransformNode::GetMatrixTransformBetweenNodes failed: expected linear transforms between nodes

Warning: In /work/Stable/Slicer-0/Modules/Loadable/VolumeRendering/MRMLDM/vtkMRMLVolumeRenderingDisplayableManager.cxx, line 754
vtkMRMLVolumeRenderingDisplayableManager (0x68fcd60): GetVolumeTransformToWorld: Non-linear parent transform found for volume node MRHead

```

This used to work, but I think there was a different transform type (maybe a grid, or a displacement field as output).

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<div class="post-metadata">

**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:** [May 30, 2022, 9:55pm UTC](https://discourse.slicer.org/t/non-linear-transforms-not-supported-for-volume-rendering/23647/2 "2022-05-30T21:55:14Z")

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I don’t believe that nonlinear transforms have ever been supported in the volume rendering. You can harden the volume first though.

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<div class="post-metadata">

**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 31, 2022, 12:38am UTC](https://discourse.slicer.org/t/non-linear-transforms-not-supported-for-volume-rendering/23647/3 "2022-05-31T00:38:44Z")

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Thanks. Perhaps I misremember. Probably hardened them…