Non Flat-Foldable Origami

Hello Everybody!

I am trying to produce a "simple" rigid folding motion in Grasshopper. As you can see in the attached file, my definition does not work (during the motion two of the four faces pull apart). I think that the problem is to find a relation that describes how the angles change during the continuous transformation of my 4-valent mesh origami. So far I read some papers about it [Tachi, 2010 _ http://www.tsg.ne.jp/TT/cg/DesignOfRigidOrigamiStructures_tachi_IAS...], but they all deal with developable and flat-foldable patterns (mine is just developable).