Team creates 3D objects that change their appearance from different perspectives

As you rotate the card and view it from different angles, imagine a birthday card that shimmers among images of birthday cake and flowers. No doubt you can think of other examples of such morphing images in commercials. So far, however, the effect has been limited to flat surfaces.

Enter the work of MIT researchers, who for the first time developed a system for creating 3D objects that change their appearance when viewed from different perspectives. The same team also developed an editing tool available free online that could allow anyone to design and build such 3D objects via 3D printing.

“Our work opens up the idea of ​​what a physical object might be,” says Yuni Zhu, an MIT graduate student in the Department of Electrical Engineering and Computer Science (EECS). “It is part of a larger vision to create dynamic objects that change their appearance, color patterns and shapes. We address appearance, which is one dimension of the concept of reprogrammable objects,” says Zhu. , who is co-first author of a paper on the work presented in October at the 2021 Association for Computing Machinery’s symposium on User Interface Software and Technology.

Stephanie Mueller is the leader of the work, an associate professor in the EECS and Department of Mechanical Engineering, and author of the paper. Mueller is also affiliated with MIT’s Computer Science and Artificial Intelligence Laboratory.

The paper’s other co-first authors are Jianni Zeng (an MIT graduate student who has graduated) and Honghao Deng (a Harvard graduate student who has since graduated). In addition to Zhu, Zeng, Deng and Mueller, the other authors are Michael Wesley, a postdoctoral associate at EECS and Axel Kilian, an adjunct assistant professor in the Department of Architecture.

“This exciting research fundamentally changes the future of product design [will] Lookalike. As an Interaction Designer, I was inspired to envision how everyday physical objects in the future could have thousands of different forms (colors and patterns) based on viewing angles. “I can think of many applications, from fashion design to aesthetic sculpting,” says Ken Nakagaki, a postdoctoral associate in the MIT Media Lab who is visiting assistant professor at the University of Chicago. was not involved in the work.

how it works

Images changing on a flat card—and now 3D objects—are thanks to many tiny lenses printed on the card or object. About six lenses made by the MIT team can fit on the surface of a penny. Known as lenticular lenses, each lens covers a pattern of small colored image spots.

“Due to the magnifying effect of the lens, this color image displays color from only one of the spots, which is only a small part of the entire area under the lens,” the authors write. What magnified space the viewer sees depends on the viewer’s point of view and the “different angles of incidence of the light hitting the lens” from that point of view. Multiple lenses together “form a lenticular display and collectively show an image that varies depending on point of view.”

The MIT team’s editing tool takes as input the 3D model, or object, that is desired as well as the images a designer wants to transform from one to another. It then calculates the lens placement and color pattern on the surface of the object that will lead to the desired effect. The designer can then preview the resulting object before sending the “direction” to the 3D printer, where the object, color pattern, and lens are all printed in one pass.

many applications

The team created four examples of 3D objects with images that change depending on the viewer’s point of view. The idea was to demonstrate the ability to create objects with different geometries, different image complexities, and varying numbers of morphing images. Display items, each of which are printed with thousands of lenses, include:

-A kettlebell for exercise that can indicate to the user whether they are holding the device properly. If the device is too low, an arrow pointing up appears; If there is too much, an arrow pointing down takes its place. The correct position is indicated with a check mark.

-A bedside lamp shade that displays different greetings depending on whether a person is sitting in bed (good day) or lying down (good night).

-A case for the EarPods that shimmers between several colored stripes depending on how the user handles it.

—Shoe printed with a motivational message that only the user can see (the message is bypassed or invisible to anyone standing nearby).

sweet spot

Zhu says the major challenge involved in the work was determining the “sweet spots” for each lens shape. “The smaller the lens, the better the resolution,” she says. “But smaller lenses also tend to have more defects, so the build quality will be worse.” Zhu and his colleagues eventually found that a lens with a diameter of three millimeters “suits most needs.”

The team also tested other parameters, including the orientation of the lens (for example, printed upwards or sideways) and various post-processing techniques for the lens. The best results were obtained by turning the lens upside down and treating it with painting varnish.

It took almost two years to take the project from concept to manufacturing of the demonstration items. The best part of the job for Zhu was “seeing that the process actually worked and holding an object in my hand. It was extremely satisfying.”