Propagation of a material through an interior volume of a three-dimensional object

An image processing system acquires a first three-dimensional model of an object. The image processing system includes a processor and storage medium encoded with instructions executable by the processor. The instructions include instructions to define a material potential function for a material. The material potential function is a function of a three-dimensional origin point of the material in the object, a three-dimensional propagation limit of the material in the object, and a three-dimensional propagation function of the material in the object. The instructions include instructions to generate a second three-dimensional model of the object based in part on the material potential function and the first model. The second model illustrates propagation of the material through an interior volume of the object at a unit level. A controller generates control signals based on the second model, and a fluid ejection engine performs an additive manufacturing process based on the control signals.