Point group D2d - Dual extruder

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In crystallography, a crystallographic point group is a collection of symmetry operations that include rotations and reflections, all leaving a central point unchanged while rearranging other directions and faces of the crystal to take on the positions of identical features. A dual-extrusion model, this is characterized by a tetragonal cell. It's classified in Schoenflies notation as D2d (Vd) and in Hermann-Mauguin notation as −42m. The orbifold notation for this group is 2*2. Custom cells can be created using the included OpenSCAD files. Further information on crystallographic point groups like D2d can be found at https://www.staff.ncl.ac.uk/j.p.goss/symmetry/D2d.html