1. A method comprising: moving an item to be purchased, along a path, the item having an irregular surface; capturing first 2D image data from the irregular surface when it is at a first position along the path; capturing second 2D image data from the irregular surface when it is at a second, different, location along said path; processing the first and second 2D image data, in conjunction with information related to said path, to discern first 3D spatial orientation information for a first patch on the surface; processing the first and second 2D image data, in conjunction with information related to said path, to discern second 3D spatial orientation information for a second patch on the surface, the second 3D spatial orientation information being different than the first 3D spatial orientation information; and by reference to said discerned first and second 3D spatial orientation information, decoding a machine-readable identifier on the irregular surface, the identifier spanning at least a portion of the first patch and a portion of the second patch.