I tried using the vtkAppendFilter with a common root node, but ran into problems that turned out to be a bug in the caching: Update is called on the common root node for both descendant nodes, creating two instances of the root object and the input/properties are only applied to one of the copies of the common root node, resulting in a missing vtkobj (None) down the line.
The attached images show the error and how to reproduce it (Calling update on mixed will fail). I will upload my suggested hotfix for this issue.
I tried using the vtkAppendFilter with a common root node, but ran into problems that turned out to be a bug in the caching: Update is called on the common root node for both descendant nodes, creating two instances of the root object and the input/properties are only applied to one of the copies of the common root node, resulting in a missing vtkobj (None) down the line.
The attached images show the error and how to reproduce it (Calling update on mixed will fail). I will upload my suggested hotfix for this issue.