Here I offer a possible solution to Youtube user mcwolle's rendition of Escher's perpetual waterfall. Here's the vid:

There has been posted a "solution" to this video posted by user origamimavin using 3d modelling software, but his model is incorrect. If you have seen his model, refer to his point (B). Now refer back to that point when his model is shown from the front as a completed illusion. The right column near his point (B) needs to be on the other side of the trough. Therefore, his representation is not valid.

Read on for my proposed solution using photo editing software...