Cross Mesh Field Evaluation

> There's something I've been wanting to do in VisIt but I do not know if
> it's possible.
>
> I have an image of the earth as a 2D projection (it's a jpeg).  I also
> have a 3D spherical representation of the earth as a mesh in a .SILO
> file.  I would like to wrap the jpeg over the mesh.  Would I need to
> embed the jpeg in a silo file (if that's possible) or is there any other
> way to make this wrapping occur?  Any help is much appreciated.  Thanks!

Hello <customer>,

There are two methods for taking a field from one file and mapping it to the mesh of another file. In this case, we'd be thinking about taking a field from the JPEG and putting it on your 3D mesh in the Silo file. It's likely that neither of the methods are a match, but I'll explain them both.

Both involve using VisIt's expression language. Both do what VisIt calls CMFEs (cross-mesh field evaluations).

1) conn_cmfe: Assume that the underlying connectivity of the meshes from the two files are the same and simply place the field from one onto the other. For point data, this means that the value at point K of the recipient mesh is always going to be the same as the value from point K of the donor's mesh. This is true regardless of where the "points K" lie in space. For cell data, this means that the value at cell K of the recipient mesh is always going to be the same as the value from cell K of the donor's mesh. Again, this is true regardless of where the "cells K" lie in space.

If your JPEG and Silo mesh have identical connectivities, then this is the option for you.

2) pos_cmfe: This is a position based CMFE. For point data, assume that a point K of the recipient mesh lies at (X, Y, Z). Then the value at point K of the recipient mesh is going to be the same as the value at the location (X, Y, Z) of the donor's mesh. For point data, assume that a cell K of the recipient mesh has its center at (X, Y, Z). Then the value at cell K of the recipient mesh is going to be the same as the value at the location (X, Y, Z) of the donor's mesh.

This option probably won't help you much, unless you want to take your Silo file, project it to 2D, try to evaluate the expression then (using the DeferExpression operator), and then project it back. We'd have to think hard about how to even do that.


I doubt either of these are going to be good solutions, so it likely does mean that you're going to have to put the JPEG info in the Silo file.