This is another perfectly symmetrical illusion, the first one being the Penrose tribar. Peculiar things happen when all three vanishing points are at the same distance from the center. Lines start to line up between different depths and it makes things a bit bothersome as geometry seems to flow together at the wrong places. This is the reason why there are chamfered corners present here.
Spiral5
2012-09-23
Linework | Fillwork
Three flat objects are bound to each other in a way that should not be possible.
Óscar on 
Heh
Smart with the chamfers.
I’ll start incorporating them, see how it flows.