By pressing 'Shift' simultaneously clicking the "Roughness" button, the Abbot Firestone curve will be shown.
Example of Abbot Firestone curve
The Abbott-Firestone curve or bearing area curve (BAC) describes the surface texture of an object.
The curve can be found from a profile trace by drawing lines parallel to the datum and measuring the fraction of the line which lies within the profile.
Mathematically it is the cumulative probability density function of the surface profile's height and can be calculated by integrating the profile trace.