Database plugin rectilinear mesh ghost data

[benjaminjeliot]

Hello everyone,

I am currently developing a VisIt database plugin and I am trying to load rectilinear meshes with ghost zones.

The data format I am loading allows for multiple ghost zone layers/halos on a rectilinear mesh. The number of ghost layers/halos on the variables can differ from the mesh. For example, the mesh might have one layer of ghosts but a variable has zero.

How can I handle this case in VisIt?

Is it possible to correctly handle a variable where the dimensions don't match the mesh?

From what I understand, it is possible to get VisIt to generate ghost data when it is required. Can this be used on a per-variable basis?

Thanks,
Jim

[biagas]

Here is a link to our wiki on representing ghost data within VisIt, if you aren't already familiar with its content.

The SAMRAI plugin might serve as example for the kind of ghosting you are after, or how to handle different levels of ghosting on mesh vs variables defined on mesh.

If your variable dims don't match the mesh, eg # values in var array < than #zones/nodes in mesh, you might need to set up handling of Missing Data. Also take a look at Missing Data Implementation.

[brugger1]

The ghost data is added to the VTK dataset returned from the GetMesh method in the reader. The issue is that you only have the mesh name (and possibly the time state and domain depending on the type of reader). Fortunately, there is a method called RegisterVariableList, that is called before GetMesh, that passes the name of the primary variable and a list of secondary variables. If you cache the primary variable name, you can use that to determine the ghost zone information to return.

[benjaminjeliot]

Thank you both for your replies.

I added a RegisterVariableList method in the plugin. The SAMRAI plugin was a useful example of how to override the CanCacheVariable method, to turn off caching for the mesh. I can now correctly size the mesh to the variable in the GetMesh method.

It's all working perfectly now. Thank you for your help!

Kind regards,
Jim :-)

[brugger1]

You're welcome. Glad to help.