1. Method for detecting the foreground or background vector near a discontinuity in a vector field, characterised in that it is determined whether covering or uncovering situation exists, that at the position {right arrow over (x)} 1 of the discontinuity a first position {right arrow over (x)} a in the previous (covering) or next (uncovering) vector field is calculated by shifting {right arrow over (x)} 1 over the first vector at one side of the discontinuity, a second position {right arrow over (x)} b in the previous (covering) or next (uncovering) vector field is calculated by shifting {right arrow over (x)} 1 over the second vector at the other side of the discontinuity and a third intermediate position between {right arrow over (x)} a and {right arrow over (x)} b is calculated, in which the vector fetched with v {right arrow over (a)}v at the third position in the previous (covering) or next (uncovering) vector field is the background vector.