In the field of X-ray imaging the 3D image data generation solves the task to produce a data set from measured two-dimensional images, which represents a characteristic of the material point by point in the three-dimensional space. These points are described by real figures referring to volume elements (short: voxels) on a three-dimensional Cartesian grid. The voxel-by-voxel calculation of the material characteristic in a volume is called reconstruction and is done computer-based.