= Mesh !MetaData = == Where should the Mesh !MetaData Reside? == 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. == What should be included in the Mesh !MetaData? == * Spatial Dimension and Topology * names of coordinate variables * name of coordinate type * Cell type (types) == Discussion == === Spatial Dimension and Topology === ''' Spatial Dimension ''' :: ''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] ''' Topological Dimension ''' :: ''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] === Name of Coordinate Variables === 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. === Name of Coordinate Type === 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: * z-coordinates vs sigma-coordinates * lat/lon vs projection The types should be enumerated and standardized as part of the Unstructured Grid convention? === Cell Type === see CellType == Example CDL for the connectivity variable == === Two dimensional triangular Mesh === {{{ int MESH A(nConnect_A, nCells); MESH A:Standard_Name = "Connectivity" MESH A:Spatial Dimension = "3" MESH A:Topological Dimension = "2" MESH A:X nodal coordinate = "x_A" MESH A:Y nodal Coordinate = "y_A" MESH A:Z nodal Coordinate = "Z_A" MESH A:Cell Type = "NC_TRI" }}} === Extruded two dimensional triangular mesh === {{{ int MESH B(nConnect_B, nCells) ; MESH B:Standard_Name = "Connectivity" MESH B:Spatial Dimension = "3" MESH B:Topological Dimension = "3" MESH B:X nodal coordinate = "x_B" MESH B:Y nodal Coordinate = "y_B" MESH B:Sigma_Coordintes = "Sigma" ! Name of sigma coordinate variable MESH B:Sigma_surface = "Surface" ! Name of surface height variable MESH B:Sigma_bottom = "Bottom" ! Name of sigma bottom depth variable MESH B:Sigma_equation = "Your equation here" MESH B:Cell Type = NC_tri }}} === Mixed three dimensional cell mesh === {{{ int MESH C(nConnect_C, nCells) ; MESH C:Standard_Name = "Connectivity" MESH C:Spatial Dimension = "3" MESH C:Topological Dimension = "3" MESH C:X nodal coordinate = "x_C" MESH C:Y nodal Coordinate = "y_C" MESH C:Z nodal Coordinate = "Z_C" MESH C:Cell Type = "NC_UNSTRUCT" MESH C:Mixed Cell List = "Mesh C Types" }}} '''Go Back to''' CdlDiscussion '''Table of Contents'''