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One of the teamLab exhibitions, probably: https://www.teamlab.art/e/

2013 https://futurepark.teamlab.art/en/places/ryubo/

They have it in several other places.

Our family did this recently as well at teamLab Planets in Tokyo. I filled out a circular template with a very creepy looking "smiley" face. The template turned out to be for raindrops. I couldn't stop giggling when hundreds of my monstrous creations filled the room, it was very fun.

The Singapore ArtScience museum has this concept. Templated sea animal colour in pages that a guide vetted before scanning and then your fish appears on the walls of the dark room in a sea life picture swimming with all the other fish. It was pretty cool. A variation in the other room was the same deal but with flying machines, but this time they gave you a remote control that controlled specifically your creation as it flew around on the landscape projected onto the walls.

I found https://dibulo.com - where you (ok and kids) can do it at home :)

Teamlabs - Borderless, I also did the same : )

yep that was it!