A Bent Tube is a circular-cross-section tube that can have simple bends. It is like a pipe or a cylinder but with bends. The primary purpose is to model steel tubes that hold marine canvas. Bent Tubes are marked on photos by marking one edge and defining multiple 'widths' to define other edge. The edge being marked is the silhouette of the tube - where the tube meets the background (not to be confused with the Silhouette entity in PhotoModeler).