The routine plpsty may be used to select either a solid fill or from 1 of 8 predefined area line fill patterns. Additional area line fill patterns using one or two sets of parallel lines at arbitrary inclinations and spacings can be specified with the routine plpat The (redacted) arguments to this routine are the integer inc and del vectors specifying the inclinations in tenths of a degree and the spacing in micrometers of the pattern(s). Thus to specify an area line fill pattern consisting of horizontal lines spaced 2 mm apart the inc vector should have single element set to 0, and the del vector should have a single element set to 2000. And to specify an area line fill pattern consisting of a symmetrical crosshatch with lines directed 30 degrees above and below the horizontal and spaced 1.5 mm apart, the inc vector should contain the elements 300 and -300, and the del vector should contain the elements 1500 and 1500.

N.B. Solid fills use the current (semitransparent) color and line fills use the current line style, width, and (semitransparent) color. The result is PLplot users have a large choice of different fill patterns.