According to some embodiments, a computer processor may receive an item definition file containing a volumetric description of the three-dimensional item and create a compressed item definition file including a compressed volumetric description of the three-dimensional item. For example, the item definition file may include a plurality of item slices, from a bottom item slice to a top item slice, each item slice describing a two-dimensional portion of the three-dimensional item. For at least some of the item slices, the computer processor may encode data in the item definition file describing a particular item slice in terms of differences between that particular item slice and another item slice (e.g., a neighboring item slice directly below that particular item slice or an anchor item slice below that particular item slice).