I saw a tutorial on the web, and they showed this image as an example, without explaining how they did it. they explained how to use the network tool with a simple set of lines, and showed this afterwards as a more complex example of what is possible.

I tried to recreate this, since I found it strange that the sharp crease of those half protruding tubes suddenly changed into a smooth transition. but I did not succeed in getting the same result.

Any ideas what I did wrong? or did they use an other tool after all?

tnx
wim