In GiD Postprocess you can study the results obtained from a solver program. The solver and GiD Postprocess communicate through the transfer of files. The solver program has to write the results to a file that must have the extension .post.res and its name must be the project name. Other allowed extensions are .post.lst,.post.bin and .post.h5.
The solver program can also send the postprocess mesh to GiD (though this is not mandatory), in the same .post.res,.post.bin or .post.h5 file or in a separate .post.msh acii file. If this mesh is not provided by the solver program, GiD uses the preprocess mesh in Postprocess.
Other files with the extensions .msh,.res,.bin,.lst,.h5 can be readed into postprocess but only those with the .post sufix are automatically read into GiD when entering the post-process model
Postprocessing data files can be:
- ASCII files, where the mesh and results should be provided in two separated files;
- binary files, a binary version of the ASCII files but mesh and results can be stored in one file;
- hdf5 files, mesh and results are stored in one hdf5 file.
All three formats can be writen using the freely available GiDPost library, whose source code, and some pre-built binaries, can be downloaded from https://www.gidhome.com --> GiDPlus --> GidPost.
From now on the explanation will be focused in the ASCII format. The details about the binary and hdf5 format are explained afterwards in a separated section.
The ASCII format consists of two files:
- Mesh Data File:
project_name.post.mshfor volume and surface (3D or 2D) mesh information, and
- Results Data File:
project_name.post.resfor results information.
Note:ProjectName.post.msh handles meshes of different element types: points, lines, triangles, quadrilaterals, tetrahedra and hexahedra.
If a project is loaded into GiD, when changing to GiD Postprocess it will look for ProjectName.post.res. If a mesh information file with the name ProjectName.post.msh is present, it will also be read, regardless of the information available from GiD Preprocess.
- ProjectName.post.msh: This file should contain nodal coordinates of the mesh and its nodal connectivities as well as the material of each element. At the moment, only one set of nodal coordinates can be entered. Different kinds of elements can be used but separated into different sets. If no material is supplied, GiD takes the material number to be equal to zero.
- ProjectName.post.res: This second file must contain the nodal or gaussian variables. GiD lets you define as many nodal variables as desired, as well as several steps and analysis cases (limited only by the memory of the machine). The definitions of the Gauss points and the results defined on these points should also be written in this file.
The files are created and read in the order that corresponds to the natural way of solving a finite element problem: mesh, surface definition and conditions and finally, evaluation of the results. The format of the read statements is normally free, i.e. it is necessary only to separate them by spaces.
Thus, files can be modified with any format, leaving spaces between each field, and the results can also be written with as many decimal places as desired. Should there be an error, the program warns the user about the type of mistake found.
GiD reads all the information directly from the preprocessing files whenever possible in order to gain efficiency.