There are no keywords in the background mesh input data file (the keywords used in following subsection are just for better understanding). Everything on a line behind a # sign is treated as a comment. Any number of blank spaces may be used between individual numbers. Empty lines are ignored.
The first record contains the mesh type (only simplicial meshes are supported), element degree (only linear elements are considered, midside nodes of quadratic elements are ignored), and the overall numbers of background nodes, edges, triangles, and tetrahedrons.
For each background node, the following record describing the position of the node and associated non-negative mesh size is expected. Eventual zero mesh size specification is treated as size corresponding to the model extent.
Background edges, triangles, and tetrahedrons are described by the following records
which are repeated for each background edge, triangle, and tetrahedron. Note that the numberings of background nodes, edges, triangles, and tetrahedrons are independent always starting from one. The nodes, edges, triangles, and tetrahedrons do not have to be ordered according to their identification number, however, the ordering nodes - edges - trias - tetras is obligatory.