1. A system comprising: memory to store data and machine readable instructions; a processor to access the memory and execute the machine readable instructions, the machine readable instructions comprising: a phase calculator programmed to compute phase values for electrical signals at each of a plurality of nodes distributed across a geometric surface corresponding to patient tissue; a mask generator programmed to generate an activation mask for a given node of the plurality of nodes specifying a set of at least one activation time period having a beginning time and an ending time, the beginning time corresponding to when a phase value of a signal at the least one of the plurality of nodes has a given value and the ending time corresponding to when the phase value of the signal at the least one of the plurality of nodes has another value; a candidate selector programmed to apply the activation mask to the computed phases values computed for each of the plurality nodes on the geometric surface to identify a set of focal candidate nodes; a focal detector programmed to analyze the set of focal candidate nodes to identify a given focal candidate node corresponding to a spatial location of a focal point for the geometric surface, the focal detector further programmed to generate focal point data characterizing the identified given focal candidate node; and a map generator programmed to generate a graphical map representing the focal point detected on the geometric surface based on the focal point data; and a display to receive and display the generated graphical map to visualize the focal point detected on the geometric surface.