1. An image generating system for determining respective luminance values of multiple polygons which represents a surface of a subject that is an object to be rendered by reference to a texture image attached to the multiple polygons, the system comprising: a capturing section for storing data about a texture image of an object that has been deformed by external force; a memory section for retaining a table of correspondence in which for each of multiple polygons, associated with each other are: position information about a position of one polygon which is set corresponding to a position on a surface of the object, to which no external force is applied; information about a stress vector which indicates external force applied to the position on the surface of the object and which is associated with the one polygon corresponding to the position on the surface of the object, to which external force is applied; and information about the luminance value of the texture image of the object, to which the external force is applied; and a texture mapping section for making reference to the table with the position information of the polygon corresponding to the position on the surface of the object, to which no external force is applied, and the information about the stress vector indicating a stress to act on the object.