1. A radiographic analysis method performed by computing hardware, the method comprising: receiving radiographic image data of a spherically or cylindrically symmetric object; performing a linear inversion of data derived from the radiographic image data; establishing an initial estimate for an interface location of one or more layers of the object; determining the interface location for the one or more of the layers of the object and identifications of one or more materials forming one or more of the layers of the object, wherein the interface locations are treated as continuous variables and the identifications of the one or more materials are treated as discrete variables during the determining; and outputting the one or more interface locations and the identifications of the one or more materials forming the one or more of the layers of the object.