Generating a three-dimensional representation of cardiac electrical activity within a subject's heart includes collecting, from a catheter having a distal portion that includes sensors that sense electrical activity and which catheter distal portion is positioned within a cardiac chamber of a subject, data for electrical activity sensed by the catheter distal portion while positioned within the chamber of the heart. The method also includes executing an imaging algorithm on the collected electrical activity data to generate a three-dimensional representation of cardiac electrical activity within a volume of the subject including all or a portion of the subject's heart. The method further includes displaying the imaged three-dimensional cardiac electrical activity.