1. A system comprising a plurality of electrodes; and a processing unit configured to: receive a torso-surface potential signal sensed by each electrode of the plurality of electrodes while the electrodes are distributed on a torso of a patient, project each of the torso-surface potential signals onto a respective location on a surface of a model torso based on locations of the electrodes on the torso of the patient, determine a set of cardiac activation times for a model heart within the model torso based on the projected torso-surface potential signals and a location of the model heart within the model torso, and determine a parameter of cardiac resynchronization therapy (CRT) for the patient based on the set of cardiac activation times.