1. An image processing device comprising: a calculator calculating a statistic of each of first material images among multiple initial images depicting an object; an initializer constructing a volume of the object from multiple second material images and multiple second imaging directions associated respectively with the multiple second material images among the multiple initial images; an estimator estimating the statistic associated with an observation direction from the calculated statistics; a render rendering an image by observing the constructed volume in the observation direction; a corrector correcting the rendered image based on the statistic estimated in association with the observation direction; and a constructor constructing a volume of the object from at least the observation direction and corrected image.