Automatic 2d Fillet in OpenSCAD

// This routine creates a fillet between two arbitrary shapes. // It works by expanding each shape by some distance and then creating a very thin shell around these expanded shapes. These two shells are then intersected to give one point along the fillet. The distances are chosen so that, for a two shapes that intersect under right angle, these intersection points lie on a quarter circle, with fn_fillet=16 faces.
// The hull() command is then used to hull two adjacent intersection points toge