1. A computer-implemented method of providing a volumetric representation of a three-dimensional object, the method comprising: obtaining a line list of points of at least one set of lines having start and end points corresponding to intersection of the lines with object boundary positions; obtaining an approximate volumetric representation of the object; and producing a modified volumetric representation by modifying the approximate volumetric representation based on the start and end points of the set of lines and the approximate volumetric representation.