After the pore identification step (defined by the parameters under Initialization, Pore-Fragment Reconnection, and Domain-Boundary Options), the shape of the pores is analyzed. This analysis is done by fitting ellipsoids into the identified pores.

To define such an ellipsoid, a center point and three diameters are needed.

In the following, we set

• to be the length of the longest of the three diameters,
• to be the length of the medium diameter,
• to be the length of the shortest diameter.

A pair of diameters is similar if its size ratio (the smaller diameter is divided by the larger diameter) is larger than 0.875. Two diameters differ, if their ratio is smaller than 0.875.

Four shapes for the ellipsoids can be fitted into the pore:

• An ellipsoid is formed as a Flat Bar, if all three diameters , , and differ much from each other.
• A Prolate Spheroid has one bigger diameter, , and the two smaller diameters, and , are similar to each other. Its shape is similar to a cigar.
• The two bigger diameters ( and ) of an Oblate Spheroid are similar. Thus, it can be compared to a disk.

• For a Sphere all three diameters , , and are similar.

The following figure shows the results of Pore-Shape Analysis on a porous structure. These visualizations are loaded from the Result Viewer of the *.gdr result file (under the Pore Visualization tab).

On the left, the structure is shown after pores are identified, and the pore fragments are removed at the domain boundary. The middle image shows the shapes of ellipsoids fitted to the pores. The right image shows a comparison between the identified pores (red) and the ellipsoid shapes fitted to them (gray). The matching voxels are shown in blue. This visualization provides a validation of the fitting to the ellipsoid shapes. A fitting is considered very good when a high percentage of overlap is observed, meaning the fitted ellipsoids accurately cover the pores.