GeoDict Analytic Data

Structure models in GeoDict can be described in two fundamentally different ways.

On first glance, GeoDict uses a voxel grid to describe any 3D structure, and the voxel grid is used by its modules to compute the properties. When you import a 3D image into GeoDict, or when you create a structure with any of the Geo modules, a voxel grid is produced that represents the structure. While this description is very general, it lacks any further knowledge about how the material is composed of geometrical objects. Is this a fiber? What is the direction of it, the orientation of an object? The voxel grid cannot tell the answer to these questions.

However, when a structure model is virtually created with one of the GeoDict modules, at the time of creation all the geometrical information is known. To  make use of these information later on, it is not discarded, but stored additionally to the voxel grid whenever available.

These geometric objects like spheres, ellipsoids, and fibers in GeoDict are called GAD-objects, where GAD stands for GeoDict analytic data.

In the project and status section, on the left of the GeoDict GUI, a green dot indicates that this data is available for the current 3D structure.

The properties of GAD Objects, like their diameter or position, can be written to an ASCII-file, which has the file ending .gad. A .gad file, which is easy to read and to modify, contains all the information of a given geometry.

A .gad file, written by GeoDict or an external tool, can be imported into GeoDict. During the import process, the analytic information is transformed into a voxel geometry (voxelized), where certain discretization parameters, like the voxel length, are required.

The GAD File Format

A .gad file is an ASCII file which can be opened with a text editor such as NotePad++, or WordPad. Since GeoDict 2023, the syntax is that of a python dictionary. In previous GeoDict versions, a different file syntax was used, and the old syntax can still be read and written by GeoDict 2025.

The general structure of a .gad file looks as follows:

Every gad-file written by GeoDict starts with a Header section containing details about the creator, the file, and the GeoDict version.

The keyword (or short key) NumberOfObjects specifies the number of objects in the file. The data describing each Object is given in a separate sections Object1, Object2, … later in the file.

The given Description is shown in the title of the main screen of the GeoDict GUI when the file is loaded.

In the Domain section, the size of the domain of the voxel geometry is specified, which allows GeoDict to directly load a .gad file and create a voxel geometry. The information is used as default, but can be changed during the import process when importing the gad-file with ImportGeo-Vol. The content of the Domain section is described in more detail with the Edit Domain command.

The ConstituentMaterials link the material ID with a material. The background material is defined in the Domain section, all other materials are defined in this section. All materials have a Name, a Type and an Information section. The name is a reference to materials of the GeoDict Material Database. The type is referring to a material state (solid, fluid, ..). The information could be either empty or a useful description of the material. Besides this, all properties defined in the GeoDict Material Database for this material are stored in this section:

In the MaterialDatabase section, the complete material database entries of all materials present in the structure are stored. The entries describing the materials are in the same format as the entries of GeoDict material database. This format is described in more detail in the Material Database handbook of this User Guide.

The heart and most important part of the .gad file is the list of GAD objects.

The definition of a GAD object in a file is given in the Object%1 section, where the symbol %1 stands for the index of the object. This means that the keys and values of the first object are given in the Object1 section, the keys and values of the second object are given in the Object2 section, and so on. The NumberOfObjects given above has to correspond to the number of sections defined here.

Each GAD object has some common keys:

• The MaterialIDModel defines of how many different materials an object consists. Typically, it is just one ID and the value is Constant. Some non-constant patterns are also possible, see the description of the Change Material ID Model command for details.
• The value after the key MaterialID specifies the material that the object is made of.
• The string after the key Type defines the type of the object, for example Sphere. The possible object types and the object-specific parameters are described in more detail with the Create / Add GAD Objects command.
• For all objects, the key Position defines the center of the objects. For objects with symmetric shapes this is also the center of mass. For objects with irregular shapes (Planar Polyhedron and Convex Polyhedron) the center is the center of the star-shaped object or the surrounding object, which may slightly differ from the center of mass.

Other parameters depend on the object type and are given as key-value pairs where the value can be a floating number, an integer number, a Boolean value (true or false), a vector, or a string. Each key-value pair has to be put in a separate line, where the order of the lines is not important (the key-value pairs of an object can be interchanged). The possible object types and the object-specific parameters are described in more detail with the Create / Add GAD Objects command.

• If the key Diameter is used to specify a parameter of a gad-object, it is always possible to use instead the key Radius and half the value of the diameter. This is a convention respected by all gad-objects.