What is the purpose of getNodeXi member of a shape function about core

[ibaned]

The reason it has very little code in it is that the "int node" argument is actually indexing the interior nodes of the entity. So, for quadratic Lagrange, the only valid queries are interior node #0 of a vertex, or interior node #0 of an edge, i.e. the mid-edge node. I may be forgetting all the code I've written, but I don't think there is a function for indexing over all the nodes in the closure. Most Finite Element code starts with the Xi of a quadrature point as input and evaluates shape functions, so this otherwise simple functionality has so far been left out.

[ibaned]

Could you give some background on why you're making this query in your code ? I know its a simple one but it would be a bunch of new tables somewhere so I'd like to know the use case.

[YetAnotherMinion]

I was looking for a way to display the stress and strain fields using Paraview. In order to use the built in rendering/warp vector, I need to find the stress and strain for the element nodes in global coordinate space. This way I can write the output.I looked at using the IPShape field to store the output variables, but it creates many different fields and I can only warp vector or color with one of them. Thus I was motivated to evaluate the secondary variables at the node points.

I can create a table in my application code to give me the locations of the nodes for all of my supported shape functions, but I wanted to see if there was a feature of the API that would do this for me. getNodeXi sounded exactly like what I wanted to do, but I understand now the intended use. Thanks for the quick response!