Hi all,
I am working on visualization of topological features and I have hit a VTK
wall. I have a 2D structured grid that has been built into a
vtkMutableDirectedGraph with the vertices as the nodes and the connections
between vertices as the edges (not all vertices will end up connected
eventually). I am trying to create a breadth-first search tree from my graph so
then I can find leaf nodes and prune them unless they meet certain criteria.
I am working in Python but have been digging through the VTK C++ examples to
figure out how to do it. The example for the vtkBoostBreadthFirstSearchTree
says it can be used to convert a graph into a tree so that's what I have tried.
My code to do the conversion looks like:
bfs_tree = vtk.vtkBoostBreadthFirstSearchTree()
bfs_tree.SetOriginVertex(0)
bfs_tree.SetInput(self.graph)
bfs_tree.Update()
tree = bfs_tree.GetOutput()
This appears to work (no errors are thrown). I then try to iterate over the
tree to find the leaves. I create and loop over my iterator with:
tree_iterator = vtk.vtkTreeBFSIterator()
tree_iterator.SetStartVertex(0)
tree_iterator.SetTree(tree)
while tree_iterator.HasNext():
node = tree_iterator.Next()
print node, tree.GetLevel(node)
where my print statement is just to debug what is happening. The printout looks
like:
0 0
1 1
2 2
3 3
4 4
5 5
so my tree is just a straight line. This is a 20x20 fully connected (for now)
structured mesh, so my tree should have more than 5 nodes to it and shouldn't
be a straight line.
Am I missing something in how this works? Or have I gone about this in a
totally backwards way?
Related question -- will the value of the node from the iterator match that of
the graph or does the tree renumber things?
Thanks,
Tim
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