A directed curved line consisting of line segments and arcs (including the edges of the model). Contours are used to display X-Y plots or tables, and to calculate integrals.
Rules applied to the contours:
Contour may not intersect itself.
Open and closed contours are discerned.
Multiply connected contours have sense only for calculating integral quantities.
Contour is shown in the window as a set of directed lines or color-filled interior (closed counter-clockwise-directed contours).