FIGURE 8. Extraction of the internal volume of the shell. 1. Creation of the stopper at the place of a plane placed at the mature constriction of the shell. This constriction is the nearest closed aperture outline from the final shell aperture. 2. Selection of the internal volume of the shell, which is constrained by the shell itself and by the numerical stopper. 3. The data volume is now described by three segments: the shell itself, the stopper, and the internal volume of the shell. The data volume of the shell has now a size of 588 × 561 × 455 voxels. Thickness of the shell is exaggerated on the figure.