Shallow copy a node into a scene

ebrahim · October 11, 2021, 4:56pm

I’ve created a scene and I want to copy nodes from the current scene into my new scene.
But I don’t want to copy any underlying bulk data in the nodes. I want new nodes that refer to the same underlying data when there is any. Is this possible in the current api with vtkMRMLScene or vtkMRMLNode?

vtkMRMLScene::CopyNode seems to do a deep copy.

jcfr · October 11, 2021, 5:19pm

Looking at the CopyContent function should be helpful:

github.com

Slicer/Slicer/blob/03e913587bf7b78990f0224bc77818e3ed31d5d3/Libs/MRML/Core/vtkMRMLNode.h#L237-L246

    
      
          /// \brief Copy node contents from another node of the same type.
          /// Does not copy node ID, Scene, Name, SingletonTag, HideFromEditors, AddToScene, UndoEnabled,
          /// and node references.
          /// If deepCopy is set to false then a shallow copy of bulk data (such as image or mesh data) could be made;
          /// copying may be faster but the node may share some data with the source node instead of creating
          /// an independent copy.
          /// \note
          /// If a class implements this then make sure CopyContent and HasCopyContent methods are implemented
          /// in all parent classes by adding vtkMRMLCopyContentMacro(ClassName) to the class headers.
          virtual void CopyContent(vtkMRMLNode* node, bool deepCopy=true);

ebrahim · October 11, 2021, 6:05pm

I thought this might help, but the deepCopy parameter doesn’t get used. And I’m not seeing CopyContent get overriden by descendants of vtkMRMLNode. Maybe I am missing something-- I will test and see if it really does a shallow copy.

ebrahim · October 11, 2021, 7:14pm

I was indeed missing something:
CopyContent does get overriden, the override was just tucked into the macro vtkMRMLCopyContentMacro.

Thanks @jcfr, I think this should do what I need!

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Shallow copy a node into a scene

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