Documentation/Nightly/Developers/FAQ/MRML

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MRML

How to add a MRML node into the scene ?

  • Generic pattern
vtkNew<vtkMRML???Node> nodeToAdd;
...
mrmlScene->AddNode(nodeToAdd.GetPointer());
  • Add a polydata to the scene
vtkNew<vtkMRMLModelNode> modelNode;
modelNode->SetPolyData(polyData);
mrmlScene->AddNode(modelNode.GetPointer());
  • Load a polyData from file
vtkSlicerModelsLogic* modelsLogic = ...;
//modelsLogic->SetMRMLScene(mrmlScene);
modelsLogic->AddModel(polyDataFileName);

What to do if you get 'No LookupTable was set but number of components in input doesn't match OutputFormat' when loading a MRML scene ?

If you get the following error messages:

ERROR: In /path/to/VTK/Imaging/vtkImageMapToColors.cxx, line 153
vtkImageMapToColors (0x268f190): RequestInformation: No LookupTable was set but number of components in input doesn't match OutputFormat, therefore input can't be passed through!

ERROR: In /path/to/VTK/Imaging/vtkImageExtractComponents.cxx, line 239
vtkImageExtractComponents (0x26947e0): Execute: Component 1 is not in input.

ERROR: In /path/to/VTK/Imaging/vtkImageExtractComponents.cxx, line 239
vtkImageExtractComponents (0x26947e0): Execute: Component 1 is not in input.

[...]

Make sure the colorNodeRef attribute is set on each VolumeDisplay node.

How to change the volumes in the 2D views ?

appLogic = slicer.app.applicationLogic()
selectionNode = appLogic.GetSelectionNode()
selectionNode.SetReferenceActiveVolumeID(bg)
selectionNode.SetReferenceSecondaryVolumeID(fg)
appLogic.PropagateVolumeSelection()

Source: https://github.com/fedorov/ChangeTrackerPy/blob/master/Wizard/Helper.py#L82

How to know the min/max offset of a slice view ?

vtkMRMLSliceNode* redSliceNode = vtkMRMLSliceNode::SafeDownCast( this->GetMRMLScene()->GetNodeByID( "vtkMRMLSliceNodeRed" ));
vtkMRMLSliceLogic* sliceLogic = this->GetMRMLApplicationLogic()->GetSliceLogic( redSliceNode );

double sliceBounds[6] = {0, -1, 0, -1, 0, -1};
sliceLogic->GetLowestVolumeSliceBounds(sliceBounds);
double min = sliceBounds[4];
double max = sliceBounds[5];

Source: https://github.com/Slicer/Slicer/blob/master/Libs/MRML/Widgets/qMRMLSliceControllerWidget.cxx#L1267-L1276