1. An image generating system for determining the luminance value of an object's polygon by reference to a texture image, the system comprising: a capturing section for storing data about a texture image representing a subject 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 where one polygon, to which no external force is applied, is located; information about a stress vector indicating external force applied to the position of that polygon; and information about the luminance value of a texture image when the external force is applied; and a texture mapping section for making reference to the table with the position information of the object's polygon, to which no external force is applied, and the information about the stress vector to act on the object's polygon.