Creates an airbag model (composed of six surfaces) out of a single surface.
model = EXPAND(
oldmodel, number, width, thickness
) ;
model
The airbag model.
oldmodel
The model containing the airbag surface.
number
The number of the surface (within oldmodel) to be expanded.
width
The width of the border zone created close to the airbag's outline.
thickness
The thickness of the airbag model.
The ''expansion'' means creation of the ''upper'' and ''lower'' surfaces and of the border zone joining the initial contour with these surfaces. Both the ''upper'' and ''lower'' border zones are composed of two pieces in order to avoid surfaces with holes (simply connex surfaces are easier to cut when folding).