Fairing of surfaces with optimization techniques using FANGA curves as the quality criterion (Q687332)

The neologism `fairing' used by the authors means `giving a surface an acceptable visual appearance'. They are mainly interested in shapes used for aircraft design. Surfaces given graphically have to look acceptable in their environment, in particular for fitting to other parts, curvature properties, etc. Most of the work done in computer aided design in the definition of surfaces is in working out detailed adjustments of parameters. The authors propose to speed up this very time-consuming process by running a check on every new surface whether it conforms with engineering standards of `fair looks' and they find the following method useful: Cut the surface patch by a sequence of (equally spaced) planes and look at 5 angles defined on the intersection curve: the angles of initial and terminal tangents and the chord subtending the curve with the vertical, the angles between the latter chord and the chords drawn from the endpoints to the midpoint of the curve. If the values of these angles are graphed and the resulting curves are not very smooth then the model surface has to be discarded.