[visit-developers] 2d meshes and 3d vectors

Tom Goffrey t.goffrey at exeter.ac.uk
Wed Jul 22 16:41:29 EDT 2015


I don't know Sveta's set-up, but this occurs in 2.5D MHD. Here, for
example, variations only occur in the x-y plane, however the z-component of
the B-field and the velocity vector are both important, and also vary in
the x-y plane.


On Wed, Jul 22, 2015 at 9:30 PM, Miller, Mark C. <miller86 at llnl.gov> wrote:

>  Hi Sveta,
>  Hmm. I see the picture and think I understand the meaning of 3D vectors
> on a 2D mesh.
>  I am just trying to understand what the source of that data is? Where's
> it comming from? Whats driving the condition of having 2D mesh data with
> vectors defined on the mesh that have a 3rd component? Ordinarily, for
> purely 2D problems, only 2D entities make mathematical sense. If you are
> taking curls of vectors in 2D, then the magnitude of the result can be
> thought of as a component of a vector out of the 2D plane but that is
> really just a conceptual convenience (hxxps://
> www . physicsforums . com/threads/curl-in-2d-is-a-vector-or-a-scalar.745388/).
> Its really a scalar value that you wind up with. You don't all of the
> sudden wind up adding a 3rd dimension to a setting which was originally
> purely 2D. This is the reason for my question…why do you have 3D vectors on
> a 2D mesh to begin with?
>   From: sveta <sveta at txcorp.com>
> Reply-To: "visit-developers at elist.ornl.gov" <
> visit-developers at elist.ornl.gov>
> Date: Wednesday, July 22, 2015 1:16 PM
> To: "visit-developers at elist.ornl.gov" <visit-developers at elist.ornl.gov>
> Subject: Re: [visit-developers] 2d meshes and 3d vectors
>   Hi Mark,
> These are vectors sticking into the 3d dimension sitting on a 2d thing
> (see attached).  Yes, the mesh is 2d meaning that there are only x and y
> values.
> Thanks,
> S
>  On 7/22/15 2:10 PM, Miller, Mark C. wrote:
> First, wanna make sure what you mean by 2d mesh. You have a mesh in
> which z coord is always zero? If so, yeah, VisIt won't let you have
> vectors on that mesh with more than two components. If you don't have
> option of applying an operator of some kind (like transform with
> x-rotate by a tiny fraction of a degree), then probably best thing is to
> accomodate this in the plugin.
>  Out of curiosity thoug, can you describe the use case for 3D vectors on
> a 2D mesh? It might be best if we ultimately get rid of the constraints
> prohibiting this in VisIt.
>  Mark
>  From: Sveta <sveta at txcorp.com <mailto:sveta at txcorp.com>
> <sveta at txcorp.com%3E>>
> Reply-To: "visit-developers at elist.ornl.gov
> <mailto:visit-developers at elist.ornl.gov>
> <visit-developers at elist.ornl.gov%3E>"
> <visit-developers at elist.ornl.gov <mailto:visit-developers at elist.ornl.gov>
> <visit-developers at elist.ornl.gov%3E>>
> Date: Wednesday, July 22, 2015 12:49 PM
> To: "visit-developers at elist.ornl.gov
> <mailto:visit-developers at elist.ornl.gov>
> <visit-developers at elist.ornl.gov%3E>"
> <visit-developers at elist.ornl.gov <mailto:visit-developers at elist.ornl.gov>
> <visit-developers at elist.ornl.gov%3E>>
> Subject: [visit-developers] 2d meshes and 3d vectors
>       Hi everybody,
>       What is the best way to be able to deal with 3d vectors and their
>      magnitudes, when the mesh is 2d?
>       I could check in Vs plugin for this and create a 3d mesh if the the
>      vector has 3 components.  But is there a better way?  Can I set a mesh
>      dimensionality through some function call of VisIt?  I cannot not go
>      interactively through elevate operator as we have embeddded VisIt in
>      our
>      application.
>       Thank you,
>      SVeta
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