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Face Geometry Variable for Mixed-Topology Grids #193

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philipc2 opened this issue Dec 23, 2022 · 1 comment · Fixed by #283
Closed

Face Geometry Variable for Mixed-Topology Grids #193

philipc2 opened this issue Dec 23, 2022 · 1 comment · Fixed by #283
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@philipc2
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philipc2 commented Dec 23, 2022

#189 discusses multiple approaches to handling the_FillValue, which is used to to indicate faces with fewer nodes than MaxNumNodesPerFace for a mixed-topology grid (UGRID Conventions) Adtionally, if a face has fewer corners/edges than MaxNumNodesPerFace then the last face (column) indices shall be equal to _FillValue.

From what I've read, there doesn't appear to be a variable in the UGRID conventions that specifies the geometry of each face. However, knowing what geometry is constructed from each face is important for proper indexing and for creating geometries for visualization or locating the first instance of a _FillValue. See the figure below:

gitt

In this example, we have a mixed topology with MaxNumNodesPerFace = 6. Proposed in the introduction of a new variable i.e. Mesh2_face_geometry which would contain the geometry of each face based on the location of _FillValue. Alternately, the value representing each face would act as a maximum index for slicing, used to only return the values representing our geometry (no _FillValue is returned)

@kjnam
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kjnam commented Apr 6, 2023

Hi, Philip. We use a hybrid grid, and this would be a nice (and a necessary) feature for us. Adding a new uxarray variable seems OK if it makes the code efficient.

@philipc2 philipc2 linked a pull request Apr 18, 2023 that will close this issue
@philipc2 philipc2 added this to the Grid Topology milestone Aug 23, 2023
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