An in-texture shifting technique for correcting disagreement between the shading and the result of display of texture mapping caused during texture mapping onto a pseudo-curved surface during rendering. Not by generating a curved surface shape in a space, an equivalent effect is produced by back-calculating a curved surface shape assumed in a finally rendered image and thereby dynamically generating a distorted texture image and pasting it. This texture image generation is realized by not actually distorting the texture image but by shifting the texture image reference position of each drawing pixel during the texture mapping.
