A therapy program may be generated based on an algorithmic model of a baseline therapy field, which may represent a therapy field resulting from therapy delivery via the first therapy system based on a first therapy program. A second therapy program that controls therapy delivery by a second therapy system may be generated based on the baseline therapy field model. For example, therapy parameter values of the second therapy program may be selected to maintain at least one field characteristic of the baseline therapy field model. In some examples, the second therapy system may result from a hardware modification to the first therapy system. In other examples, the first and second therapy systems may be associated with different patients. For example, the baseline therapy field model may be an efficacious therapy field for a patient class, and a second therapy program may be generated for a patient in the class.