We present a novel approach for producing a real-time simulation of the 3D phenomenon of the electrocardiogram. Techniques are borrowed from the fields of computer vision and computer graphics to create a volumetric heart model that can be fine-tuned to illustrate a variety of electrophysiological situations. The activation sequence that occurs in the heart model is choreographed to coincide with the progression of a recorded ECG. Keywords ECG, ECG simulation, cardiac modeling, volumization, texture mapping