Methods, systems, and apparatus, including medium-encoded computer program products, facilitate creation and use of 3D models of objects with different material properties. In one aspect, a method includes specifying a continuous data format representation for a first property of an object and a discretized data format representation for a second property of the object, wherein the first property and the second property are different from each other; producing a 3D model of the object within a 3D space using the continuous and discretized data format representations, which overlap with each other in all three dimensions in at least a portion of the 3D space; and using at least one common access method into the 3D model of the object to obtain data from both the continuous and discretized data format representations, within the portion of the 3D space, to manufacture the object using one or more manufacturing processes.