PURPOSE: To provide a cloudiness preparing method for computer graphics scene display capable of satisfying both of reality and real time property.

CONSTITUTION: A gradation image shaping means 11 executes the image shaping of a gradation image inputted from an input device 6 based upon texture material data stored in a RAM 3 and prepares an image of irregular and hazy coulds. A translucent texture preparing means 12 segments a fine section in the image shaped by the means 11 based upon a segmentation coordinate value stored in a RAM 4 and expands the segmented section until the original image can not be understood. A polygon preparing means 13 prepares a polygon based upon a polygon coordinate value and a polygon material stored in a RAM 5. A texture mapping executing part 14 applys a translucent texture prepared by the means 12 to the polygon prepared by the means 13 and outputs and displays the prepared contents to/on a display device 7.