Looking for "penknife and pencil" tutorial

Hi,

Some time ago I found on the net or here in the forum, a cool tutorial to simulate a penknife and a pencil.

In thet simulation you could see the pencil that was rotated into the penknife

and little by little the pencil became shorter and shorter.

I remember that in this instance there were the video and the files that helped you understand the trick:

Can you tell me where I can find that tutorial?

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