An interactive direct response system combines the use of short text message systems via cell phones with a database and website to enable advertisers to view in real time customer responses to a direct response campaign. Three-dimensional printing includes ink-jet printing a binder into selected areas of sequentially deposited layers of powder. During a starting phase only the first gas generation unit is operated, with a power Pstart\u20141>Prated\u20141. For at least one command, its group of cells includes a cell which is to be supplied with a label of the command, a cell which is to be supplied with an expected result of the command, a cell which is reserved for an actual result of the command, and a cell which is reserved for the result of a comparison between the actual result and the expected result. Thus, a gamma correction may be provided jointly with a compensation for initial non-uniformity, degradation over time, andor non-uniform degradation to the one or more display elements of the array of display elements.