1. A computer-implemented method for determining molecular-shape of a receptor comprising: having a first molecule with a determined solvent-accessible molecular surface, wherein said surface includes a receptor which can be visualized within a computer; restricting said visualization of said surface to said receptor; said computer visualizing said molecular surface of said receptor as a plurality of small area elements; defining an initial start point in one of said plurality of small area elements and defining an initial direction; said computer having available instructions for defining a ray segment, said instructions comprising: starting an in-process ray at a start point; propagating said in-process ray in a direction until said in-process ray impacts another of said small area elements at an impact point, resulting in a ray segment between said start point and said impact point; recording characteristics of said ray segment including electrostatic properties of said impact point and said start point, said impact point, and said start point; said computer processor performing a ray-trace by repeatedly performing said instructions for defining ray segments until a plurality of ray segments is obtained wherein: in said first performance of said instructions, said start point of said in-process ray comprises said initial start point and said direction of said in-process ray comprises said initial direction; and in each subsequent performance of said instructions, said start point of said in-process ray comprises said impact point from the immediately prior ray segment and said direction of said in-process ray comprises the direction of reflection of said immediately prior ray segment from said impact point; said computer processor stopping said instructions for said in-process ray when a predetermined stop condition is met; if stopped: said computer processor restarting said instructions for said in-process ray at the same start point, and propagating said in-process ray in a direction which does not comprise the direction of reflection of said immediately prior ray segment from said impact point; and finishing said ray trace once a preselected number of ray segments have been recorded; said computer corresponding said ray segments to atoms; said computer partitioning said molecule into atom clusters; said computer decomposing said ray trace by assigning said ray segments according to results of said step of corresponding, wherein each said ray segment is assigned at least in fractional part to at least one segment corresponding to an atom cluster (an intra-cluster segment) or atoms between atom clusters (an inter-cluster segment); said computer calculating a unique probability distribution for each said intra-cluster segment and each said inter-cluster segment based on characteristics of said assigned ray segments, said probability distribution providing an indication of the shape of said inter-cluster segment or said inter-cluster segment; and said computer storing said probability distribution for later comparison to other probability distributions indicative of shapes of other molecules or portions thereof, wherein said other probability distributions are in a database.