an image processing apparatus of the present invention conducts update processing of mipmap - format texture data within an updateable range , and during drawing processing , it ascertains the level of detail to which texture data has been updated . thereupon , when conducting texture mapping , texture data of the level of detail for which updating has been completed is used . in this case , if the required texture data has not been updated , then it is substituted by texture data for which updating has been completed . consequently , even in cases where updating of all texture data is not completed in time , it is possible to prevent significant distortion of the image due to mixing of updated and non - updated texture .