Impossible Structure

We’ve seen these optical illusions a lot – they’re usually drawn because that’s what they are – just illusions in the 2d world, making you think that an impossible structure was created in a 3D space. Now, what about this one? And what if I say there was no Photoshop involved? How can it be done?
[Answer here]
[...] Via: Gemstys [...]
The link doesn’t seem to work
Awesome, but you can see how this is done, just look at the shadows – not all of these element are connected