OpenSCAD Library: Parametric joint generator

An addition to the OpenSCAD library, which can be used to create right angle T-joints, which are preferred over simple rectangular "face-on" connections: their stability against breaking off the leg is much higher. This isn't just due to the added material: Same principle applies and can be observed with, for example, a rip in a piece of fabric. A right angle connection of a simple stick-on joint corresponds to the rip - when undealt with, does the rip easily propagate along and further into the fabric. Quick measure against further damage is to cut a round opening at the crest of the rip - now tearing forces are distributed all away around the hole, rather than concentrating on the crest.

The semispherical connection points of these joints do the same kind of force distribution, thereby increasing robustness of legs attached with these.

The file is meant to go into the OpenSCAD library, for quick and easy generation of joints.
Additons to the file for supporting the thingivers