• Open GeoDict and navigate to the top menu
• Navigate to Model > GrainGeo to choose GrainGeo for structure generation.
• In the module section, click Generate.

Note: Other structure generators from the list can be utilized for this tutorial.

GeoDict is a voxel-based program, which means that structures are composed of small cubes - the same way, as an image consists of pixels.

If you are using the box or GPU renderer, the voxels become visible, when you zoom into the structure. 

• Zoom into the structure with your mouse wheel.
• Each voxel can be assigned to different materials, each possessing unique properties required for simulations.

GeoDict's structure generators create objects like spheres, ellipsoids, fibers, and more, which are needed for the simulation. These objects have the complete geometric data from the generation process, such as diameter, position, orientation, and many more. 

• This data is termed as GeoDict analytical data (GAD).
  • Therefore, these objects are named GAD-objects.
• Benefits of GAD-objects:
  • Structures can be rescaled without data loss.
  • Objects can be modified without the need to edit every individual voxels.
  • They allow powerful post-processing operations like removing overlaps or to distribute the objects in the domain.
  • This is possible, since they can be rotated and shifted without losing information. 

In the project status on the left-hand side of GeoDict the dot next to GAD Objects indicates, if GAD information is available.

• Green Dot: All solid voxels in the current structure belong to GAD-objects.
• Red Dot: No GAD-objects are present.
• Yellow Dot: Mixed presence of GAD-objects and non-GAD-object voxels.
• The number next to GAD View shows the total number of objects in the grain structure.

In GeoDict voxels and GAD-objects can be selected and edited any time. Therefore there are 2 icons in the toolbar: "Select Voxels" and "Select GAD-Objects"

• Example: Reassigning voxels in a grain.
  • Click on Select Voxels
  • Select the desired voxel.
    • Notice a blue box around the chosen voxel.
  • At the sidebar the selected voxel's precise location and material ID is shown.
  • Select multiple voxels by holding Shift or Ctrl.
  • From the pull-down menu, choose Reassign Material of Selected Voxels, select a material ID, and press Run.
  • A component consists of all connected voxels of one material ID.
  • If you want to modify the entire component to which the voxel belongs, select Flood-Fill Component after selecting a voxel.

Editing GAD-Objects is much more powerful that changing single voxels.

• To select and edit GAD-Objects click on Select GAD-objects in the toolbar.
  • Then the GAD objects selection toolbar appears on the right-hand side
• You can also select multiple objects by pressing and holding Shift, while clicking on the desired objects.
• View object details, like ID and type, in the displayed table.
• Edit Objects allows to modify material, size, or orientation of the selected objects.
  • Example: Adjust the diameter to 5 µm and click Run.
• Other editing options include changing the material ID and deleting objects.

Right-clicking anywhere in the structure opens the context menu. Here we can also select the specified voxel or GAD object and use the options of the sidebar. Additionally, we can edit the Domain. 

For this: 

• Right-Click in the structure and click Domain -> Edit Domain
• Change the domain size to 300 voxels in X- and Y-direction and click Run
• Now our structure is embedded with air
• Because the objects are GAD-Objects the structure can be rescaled without information loss.
• For this change the voxel length to 0.5 and the domain size to 400 for all three directions
• Now we have the same structure, with a much higher resolution
  • Note: There are also rescaling options for simple voxel structures, but in GAD objects it is exactly defined where to add voxels

Learn more about GeoDict by checking out other tutorials.