How to get the current ROINode programmingly according to the volume in the volume rendering module?

Development
1

Hi,all.
There are three volumes in the volume rendering module and there are three corresponding AnnotationROIs,as follows：

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yeah,I want to get the current ROINode,for example right now,I choose the first volume so I get the vtkMRMLAnnotationROINode1 and when I change to select the second volume the ROINode should be vtkMRMLAnnotationROINode2.
Usually, I hard code to get the ROINode but it is not convenient:

# get the first ROINode
AnnotationROINodeID='vtkMRMLAnnotationROINode1'
roi = slicer.mrmlScene.GetNodeByID(AnnotationROINodeID)

# get the second ROINode
AnnotationROINodeID='vtkMRMLAnnotationROINode2'
roi = slicer.mrmlScene.GetNodeByID(AnnotationROINodeID)

So,is there a way to get the current roiNode according to the selected volume?
Thank you in advance for your possible advice!

2

This should work for that:

myVolumeName = 'MRHead' # replace with the displayed name of your volume
volNode = getNode(volumeName) # get the mrml scalar volume node
vrLogic = slicer.modules.volumerendering.logic() #  get the volume rendering module logic
vrDispNode = logic.GetFirstVolumeRenderingDisplayNode(volNode) # get the volume rendering display node 
roiNode = vrDispNode.GetROINode() # get the associated ROI node

If you have an ROI node and want to know which volume is rendered using that node, you can do this

vrLogic = slicer.modules.volumerendering.logic()
vrDispNode = logic.GetFirstVolumeRenderingDisplayNodeByROINode(roiNode)
vrDispNode.GetVolumeNode()

See the documentation here: Slicer: vtkSlicerVolumeRenderingLogic Class Reference

3

Thanks Mike,
This is not working and also I have seen the documentation ,still can’t figure it out.
Maybe I am not making myself clear,my end goal is to take screenshots as png files as you helped me before.But when I load a scene.mrml file into Slicer ,there are three volumes.
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I have currently designed a GUI like this:

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I can take screenshots given the necessary parameters ,but only the first volume,which means if I select the second volume in volume rendering module and click the eye icon to see it in display area,I still take screenshots in the first volume.So what I what is as follows:
select the second volume and make it displayed:
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Is there someway to get the ROINode at the moment I selected the volume or clicked the eye icon to see it?
In other words,at the moment I selected the third volume and clicked the eye icon,the ROINode should change itself.
Thank you for your continued attention on this topic!

4

I notice there was a typo in the included code from two posts ago. I had changed a variable called logic to vrLogic to try to be a little clearer, but I didn’t change it everywhere in the pasted code. Hopefully that’s all that was leading to your errors.

vrLogic = slicer.modules.volumerendering.logic()

vol1node = getNode('vol1')
vol2node = getNode('vol2')

# Get or create the volume rendering display node for vol1
vrDispNode1 = vrLogic.GetFirstVolumeRenderingDisplayNode(vol1node)
if vrDispNode1 is None:
  # no existing display node, create a new one
  vrDispNode1 = vrLogic.CreateDefaultVolumeRenderingNodes(vol1Node)

# Get or create the volume rendering display node for vol2
vrDispNode2 = vrLogic.GetFirstVolumeRenderingDisplayNode(vol2node)
if vrDispNode2 is None:
  vrDispNode2  = vrLogic.CreateDefaultVolumeRenderingNodes(vol2node)

Then

# To show vol2 instead of vol1
vrDispNode1.SetVisibility(0) # hide vol1 rendering
vrDispNode2.SetVisibility(1) # show vol2 rendering
1 Like
5

Thanks Mike, it is not about the type error.It seems like if I want the ROINode I have to get the volumeNode by ID or name.
Thank you for your code and help anyway!

6

I think I’m not totally clear on what the problem you are running into is. I thought you were saying that the problem you were having was that the first volume rendering was being captured twice instead of switching to the second volume, so I was showing how to hide one volume rendering and show another.

Separately, once you have a volume rendering display node, you can get the ROI node from that via the GetROINode() method.