| 1 | = Mesh !MetaData = |
| 2 | |
| 3 | == Where should the Mesh !MetaData Reside? == |
| 4 | The connectivity variable of each mesh could contain the mesh meta data for each mesh in the file. If a file has three meshs (for instance: Bathymetry, Sea Surface Height, and Data) then there would probably need to be three connectivity variables anyway to describe them. The one-to-one nature makes this variable an obvious choice. The names of all the meshes in a file should be specified in GlobalAttributes. These names should corrispond to the name of the connectivity variables. |
| 5 | |
| 6 | |
| 7 | == What should be included in the Mesh !MetaData? == |
| 8 | * Spatial Dimension and Topology |
| 9 | * names of coordinate variables |
| 10 | * name of coordinate type |
| 11 | * Cell type (types) |
| 12 | |
| 13 | == Discussion == |
| 14 | |
| 15 | === Spatial Dimension and Topology === |
| 16 | |
| 17 | ''' Spatial Dimension ''' :: |
| 18 | ''The spatial dimension attribute corresponds to how many dimensions are needed to specify the coordinates for the points that make up your mesh. If your mesh exists in a 2D plane then choose 2, otherwise choose 3.'' '''Quote:''' [http://www.llnl.gov/visit/manuals.html LLNL's VisIt] |
| 19 | |
| 20 | ''' Topological Dimension ''' :: |
| 21 | ''The Topological dimension attribute describes the number of logical dimensions used by your mesh, regardless of the dimension of the space that it sits in. For example you may have a planar suface of triangles sitting in 3D space. Such a mesh would be topologiacally 2D even though it sits in 3D space. The rule of thump that Visit follows is that if your mesh's cells are points then you have a mesh that is topologically 0D, lines are 1D, surfaces are 2D volumes are 3D.'' '''Quote:''' [http://www.llnl.gov/visit/manuals.html LLNL's VisIt] |
| 22 | |
| 23 | === Name of Coordinate Variables === |
| 24 | The name of the coordinate variables used define to location of points in a mesh should be specified in the mesh meta data. This will prevent confusion in the case that there is more than one set of coordinate locations in a file to support more than one mesh. |
| 25 | |
| 26 | === Name of Coordinate Type === |
| 27 | There are a number of different coordinate types in use. Which type the mesh uses should be specified in the meta data. Some examples include: |
| 28 | * z-coordinates vs sigma-coordinates |
| 29 | * lat/lon vs projection |
| 30 | The types should be enumerated and standardized as part of the Unstructured Grid convention? |
| 31 | |
| 32 | === Cell Type === |
| 33 | see CellType |
| 34 | |
| 35 | == Example CDL for the connectivity variable == |
| 36 | |
| 37 | === Two dimensional triangular Mesh === |
| 38 | {{{ |
| 39 | int MESH A(nConnect_A, nCells); |
| 40 | MESH A:Standard_Name = "Connectivity" |
| 41 | MESH A:Spatial Dimension = "3" |
| 42 | MESH A:Topological Dimension = "2" |
| 43 | MESH A:X nodal coordinate = "x_A" |
| 44 | MESH A:Y nodal Coordinate = "y_A" |
| 45 | MESH A:Z nodal Coordinate = "Z_A" |
| 46 | MESH A:Cell Type = "NC_TRI" |
| 47 | }}} |
| 48 | |
| 49 | === Extruded two dimensional triangular mesh === |
| 50 | {{{ |
| 51 | int MESH B(nConnect_B, nCells) ; |
| 52 | MESH B:Standard_Name = "Connectivity" |
| 53 | MESH B:Spatial Dimension = "3" |
| 54 | MESH B:Topological Dimension = "3" |
| 55 | MESH B:X nodal coordinate = "x_B" |
| 56 | MESH B:Y nodal Coordinate = "y_B" |
| 57 | MESH B:Sigma_Coordintes = "Sigma" ! Name of sigma coordinate variable |
| 58 | MESH B:Sigma_surface = "Surface" ! Name of surface height variable |
| 59 | MESH B:Sigma_bottom = "Bottom" ! Name of sigma bottom depth variable |
| 60 | MESH B:Sigma_equation = "Your equation here" |
| 61 | MESH B:Cell Type = NC_tri |
| 62 | }}} |
| 63 | |
| 64 | === Mixed three dimensional cell mesh === |
| 65 | {{{ |
| 66 | int MESH C(nConnect_C, nCells) ; |
| 67 | MESH C:Standard_Name = "Connectivity" |
| 68 | MESH C:Spatial Dimension = "3" |
| 69 | MESH C:Topological Dimension = "3" |
| 70 | MESH C:X nodal coordinate = "x_C" |
| 71 | MESH C:Y nodal Coordinate = "y_C" |
| 72 | MESH C:Z nodal Coordinate = "Z_C" |
| 73 | MESH C:Cell Type = "NC_UNSTRUCT" |
| 74 | MESH C:Mixed Cell List = "Mesh C Types" |
| 75 | }}} |
| 76 | |
| 77 | '''Go Back to''' CdlDiscussion '''Table of Contents''' |