David appears to use CaRMetal https://en.m.wikipedia.org/wiki/CaRMetal https://en.m.wikipedia.org/wiki/CaRMetal CaRMetal - Wikipedia BTW, even if that's not t

David appears to use CaRMetal https://en.m.wikipedia.org/wiki/CaRMetal https://en.m.wikipedia.org/wiki/CaRMetal CaRMetal - Wikipedia BTW, even if that's not the case, I've found CaRMetal exceptionally useful for drawing similar constructions.