A disclosed method includes extracting a region from each of plural cross sections in a volume data representing a solid to be rendered, based on data of brightness values of texels for each of the plurality of cross sections, wherein the plural cross sections are perpendicular to an axis set for the volume data; deleting any one of two adjacent cross sections among the plural cross sections based on a correlation between a region extracted for one cross section of the two adjacent cross sections and a region extracted for the other cross section of the two adjacent cross sections; and rendering the solid by using data of the cross sections after the deleting.