Re: [yt-dev] Vertex-centred AMR data?

Matt In my notion, there are no cells, only vertices. Or if you want to renaming things, then there are only cells, no vertices, but the fine a coarse grid cells do not share faces. To answer your question specifically: no, it does not matter whether the centre of a "cell" is selected. Only the vertices that are selected should be part of the selection. -erik On Wed, Nov 11, 2015 at 8:57 AM, Matthew Turk wrote:

Hi Erik,

I have some ideas about this, but it relies heavily on the notion of how to regard "vertices" as separate from "cells", or if they should not be. In terms of things like visualization, vertex centered data is not a huge leap in functionality, but in terms of data selection we need to be careful. The canonical question is, if you have a region selector that includes the *center* of a zone, should all of its vertices be selected? For instance, imagine you have a region selector whose corner resides at the center of a (3D) cell. Does one select all eight vertices, since the "cell" is nominally selected, or just the one vertex that is included? If we can answer that, we can start the work of implementing.

On Tue, Nov 10, 2015 at 7:11 PM, Nathan Goldbaum wrote:

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On Tuesday, November 10, 2015, Erik Schnetter

wrote:

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I have implemented a front-end for cell-centred Cactus AMR data.

Awesome! We'd love to have this in the public distribution of yt.

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However, many Cactus simulations use vertex-centred AMR. That is, data

is

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stored at the vertices of a grid (not in the cells), and coarse vertices are at the same locations as fine vertices.

How do I present such data to yt? Do I need to set grid coordinates differently, or is there a "vertex centred" flag?

When vertex-centred data are displayed, then I expect either a "control volume" around each vertex to have the same value, or to use e.g. linear interpolation in the cells from the respective boundaries.

We don't have good support for vertex-centered AMR data. I think Matt would have a better idea of what approaches we might take here.

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-erik

-- Erik Schnetter http://www.perimeterinstitute.ca/personal/eschnetter/

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