Edges may be both ''viewpoint dependantdependent'' - these are edges that may change as the viewpoint changes, and typically reflect the geometry of the scene, objects occluding one another and so on, or may be ''viewpoint independantindependent'' - these generally reflect properties of the viewed objects such as markings and surface shape. In 2-two dimensions, and higher, the concept of a [[projection]] has to be considered.
WhileA a generictypical edge maymight be (for instance) the border between a block of red color and a block of yellow,; in contract a '''line''' iscane be a small number of pixels of a different color on an otherwise unchanging background. Essentially, thereThere will be one edge on each side of the line.
