11.5.1 Indexes that Cannot be Uniquely Determined

Subnodes, split nodes, truncation cells, and general purpose grids are the objects whose index ordering cannot be uniquely determined in a RESQML instance using the relationships in the table. In these cases, a “patch” construction is used in which elements are provided a unique patch index, and then these elements are ordered according to their patch values (for more information on patches, see 6.3 Patches ). For example, cell indexing is uniquely determined for each of the fundamental grid types shown, but when we work with a general purpose grid, multiple grid cell patches will combine to generate a single global cell index. When multiple elements of the same kind need to be combined, they are assigned a unique patch index, whose values determine the relative ordering of the data. This situation may arise even in the fundamental grids, when using subnodes for higher order finite element geometry or properties.