The internal representation of a structure in GeoDict consists of rectangular 3D arrays of cubes, hereafter called volume elements or voxels.

NX, NY, and NZ are the number (N) of voxels in X, Y and Z directions.

The Voxel Length is the size of one voxel in the chosen units. Varying the values for NX, NY, and NZ has the effect of changing the size of the structure in the given direction.

Low values for Voxel Length in combination with high values for NX, NY and NZ increase the resolution, but also increase computational time. After setting the values of NX, NY, and NZ, and Voxel Length, the physical structure size is automatically displayed in the chosen units (here µm).

The following example shows how starting with NX = 200, NY = 200, NZ = 200 (100 x 100 x 100 µm3, at voxel length 0.5 µm), and decreasing the Voxel Length from 0.5 µm to 0.25 µm has the effect of refining the structure by increasing the resolution, while decreasing the size of the volume to 50 x 50 x 50 µm3.

By setting NX = 400, NY = 400, NZ = 400, to restore the size of the volume to the original 100 x 100 x 100 µm3, the structure is displayed at higher resolution.

The Origin X, Origin Y, and Origin Z parameters, together with the Center Domain button, determine the placement of the structure in the physical space. Zero values for Origin X, Origin Y, and Origin Z mean that the point with (0, 0, 0) coordinates is located at the lower left corner of the structure.

When clicking the Center Domain button, the (0, 0, 0)-point is set to the center of the structure as shown below.

Checking the Periodic X, Periodic Y, and Periodic Z boxes allows the generation of structures which are periodic in one or several directions. Periodicity has the effect, that objects ending on one side of the volume reappear on the opposite side, so that merging of several volumes with periodic objects results in a repetitive complex.

Checking the Periodic X and Periodic Y boxes, but leaving un-checked the Periodic Z box, has the following effect on the periodicity of a generated granular structure.

This effect can be observed more closely, when processing the sample structure through Model → ProcessGeo (Repeat: X- 400 voxels, Y- 400 voxels, and Z- 400 voxels) and viewing it again from the three directions.

In the directions checked as periodic (X and Y), the short circular fibers and ellipsoids connect to each other across the repeated samples. In the direction checked as non-periodic (Z), the objects end at the edge of the sample.

Viewed from X-direction, observe the periodicity in the Y-direction, with unit cells passing smoothly into each other, and no periodicity in Z-direction, with unit cells appearing disconnected.

Viewed from Y-direction, observe the periodicity in X-direction, with unit cells passing smoothly into each other, and no periodicity in Z-direction, with unit cells appearing disconnected.

Viewed from Z-direction, observe the periodicity in the X- and the Y-directions, with unit cells passing continuously into each other in both directions.

When the material with ID 00 is chosen to be Pore, the objects are embedded in empty pore space. Alternatively, the material filling the pore space can be a Solid, a Porous medium, or Fluid, in which the structural objects are embedded. The physical properties of the pore / matrix material can be attributed for simulations. The color and the visibility / invisibility can be chosen independently of the material.