[Paraview] Finding center points/lines of a scalar field

[Tim Gallagher]

Hi everybody,

I'm working on some flow feature identification and I want to track the (x,y,t) or (x,y,z,t) centers of the features I want to identify. I can come up with a scalar field, \phi, and a criterion for my feature, say \phi >= 1. I would like to find the center point of the feature if in 2D or the center-line of the feature if in 3D. 

This can be done for a variety of different features using different scalar fields, but for sake of argument, let's say I am looking at a vortex. In 2D, the vortex core is a point. In 3D, it may for a vortex sheet, or vortex tube, it may be arbitrary in shape (horseshoe, hairpin, etc.) and so there is no center point but really a center line for the core. I suppose this line may be composed of the center point of planes spanned by two of the principle components and the center line is oriented along the third, but I am not positive.  

At any rate, given a 2D or 3D scalar field and a threshold, what are the filters I should have in my pipeline to extract this information? I plan on doing this online with Catalyst. I would imagine that it would look like:

MyData -> Threshold -> <Some filter I don't know to find the center points/lines> -> <Output each center point/line in a spreadsheet form>

I'm not adverse to programming custom filters as needed, but I feel like this is something that a filter or set of filters may already exist to make this work. I don't want to reinvent the wheel because anything I come up with won't be as efficient as what is already there!

Thanks,

Tim