Hydrographic printing is a widely used and frankly kind of nutty way to add color to objects. This new computational technique makes it even nuttier.
Standard hydrographic printing, also known as water transfer printing, starts with printing color to a sheet of thin, transparent film. You put the film on the surface of a tub of water and add some chemicals to make it soft and sticky. Then you dunk your object in the tub. As the film wraps around it, the color bonds to the object's surface.
The technique works with a variety of materials---you can plunge a motorcycle helmet, an iPhone case, a toy figurine, whatever---but there's one major limitation. Because of the way the film stretches during the dunking process, water transfer printing doesn't work for jobs that require precision. You can hydrographically paint a motorcycle helmet with little golden wings on it, but you can't be sure the little wings will sit perfectly above your ears, like Hermes's.
At least, you couldn't before. A group of researchers from Zheijiang University recently devised a clever solution to the precision problem: They simulate the stretching that happens during the plunge and bake it into the paint job beforehand.
The group calls this "computational hydrographic printing." The video above offers a nice overview. After constructing a rig to keep the dunking process uniform, the researchers developed software that simulates the stretching expected from a given object's immersion. The desired color pattern is then distorted accordingly. It's wild to watch it happen: At one point in the clip, we see a mask plunging through a Rorschach-like puddle of color. When it's pulled out, we see it's a tiger's face, now perfectly mapped to the mask's curves.
The researchers think this technique could be an easy way to add custom color jobs to 3D-printed objects, say, to turn your bright red miniature Eiffel Tower tchotchke into a more realistic miniature Eiffel Tower tchotchke. But it can also work with existing objects. The researchers bought a porcelain mug at a store, 3D scanned it, and used their system to give its elephant-head handle a cute, colorful face. As part of the study, they researchers developed a "multi-immersion" system that can apply more three-dimensional paint jobs to objects over the course of several dunks.
Whether or not computational hydrographic printing brings color to the maker revolution, it's an odd pleasure to see in action. The thrill has something to do with overcoming the uncertainties you'd think were inherent in the process of painting a thing by dunking it in a tub of water. Watching the colors warp perfectly into place, their patterns algorithmically deranged in anticipation of the predictable liquid encounter, the whole thing almost feels, I don't know, mischievous.
