Plotting contour surfaces of a function of three variables

A technique is presented for the graphical representation of some contour (level) surfaces of a function of three variables defined by its values on an array of points (<italic>x<subscrpt>i</subscrpt></italic>, <italic>y<subscrpt>j</subscrpt></italic>, <italic>z<subscrpt>k</subscrpt></italic>). The algorithm involves drawing and projecting the contour curves corresponding to the cross sections <italic>x</italic> = <italic>x<subscrpt>I</subscrpt></italic> and <italic>y</italic> = <italic>y<subscrpt>j</subscrpt></italic>. Because the curves are drawn as thick, opaque bands, which mask all bands in the immediate background, a sense of depth is retained, yet background contours are still visible between the bands.