1. A program product encoded in a computer-readable medium that when executed by the computer causes the computer to execute processing of mapping a texture containing a plurality of spectators to a plate-shaped polygon arranged in a plurality of areas in a virtual three-dimensional space, and generating an image containing said plurality of spectators; wherein said program product causes said computer to function as: a spectator information setting unit for setting spectator information including at least the number of spectators belonging respectively to first and second spectator types, and a color type associated respectively to said first and second spectator types; a spectator distribution unit for determining the number of spectators belonging to said first and second spectator types to be allocated respectively to said areas in said virtual three-dimensional space; a mixture ratio determination unit for determining the mixture ratio of said first and second spectator types in each of said areas in said virtual three-dimensional space; a polygon determination unit for determining a plate-shaped polygon to be arranged in said areas and mapped with a texture containing a plurality of spectators; a pallet data determination unit for determining color pallet data associated with the color of said texture based on said color type included in said spectator information so that the ratio of said spectators belonging respectively to said first and second spectator types contained in said texture achieves a state according to said mixture ratio; a mapping unit for mapping said texture defined based on said determined color pallet data to said plate-shaped polygon determined by said polygon determination unit; and an image generation unit for generating a two-dimensional image containing said plurality of spectators obtained by performing perspective projection on a perspective projection plane set in correspondence with a viewpoint of a virtual camera arranged in said virtual three-dimensional space.