Dec 18, 2015 | By Kira
Justin Jensen, a Brigham Young University Master’s of Computer Science Candidate, has been studying computer graphics and animation for years, and was used to seeing his work “born, live, and die” in the virtual world. Seeking to create something more tangible—a 3D object that he could hold in his hands, view from all angles, and physically interact with—he found his way to 3D printing. Inspired by the technology and by a plastic Star Wars: Episode 2 toy from a Dorito bag, of all things, he devised a method for creating 3D printed versions of digital photographs that, when lit from behind, reproduce the original image with a high level of fidelity—also known as a 3D printed lithophane.
A lithophane is actually a centuries-old art form in which an image is represented through an etched or molded piece of translucent porcelain, and can only be seen when lit from behind. The lighter the area in the photograph, the thinner it is etched or molded so that more light can come through, whereas darker areas are left thicker. The result is a three-dimensional image that, depending on the attention to detail, can reveal a surprising amount of depth.
Though lithophanes have been around since the 1800s, they weren’t what inspired Jenson. At least, not exactly. “When I was a kid and Star Wars Episode 2 was about to be released, you could find these little plastic puzzle pieces in bags of Doritos chips,” he told me. “When you held them up to the light, the image of a Star Wars character would appear. That was the inspiration for this project. I wanted to do the same thing with my own images, but with larger prints.” I myself wasn’t aware of lithophanes before seeing this cool project, but I’m happy to have found out that not only are they quite beautiful, but that through the level of detail afforded by SLA 3D printing, designers can recreate a wide variety of photos with a very high level of fidelity.
Jensen developed the process for 3D printing photographs in the course Advanced Human Computer Interaction at BYU. The course is comprised of three major units: rapid prototyping; fundamental theories of HCI; and finally lessons in how to use a laser cutter and 3D printer to being human-computer-interaction projects to life.
In order to create his 3D printed lithophanes, Jensen began by converting a color image to grayscale using its luminosity. He then created a rectangular mesh of triangles, where each pixel in a source is represented by a vertex in the triangular mesh. In order to define which areas would be 3D printed thinner or thicker to allow for varying degrees of light to pass through, he set the Z coordinate of each vertex to be inversely proportional to the brightness of the pixel. (“Brighter pixels will have a smaller Z value, which translates to a thinner print and more light transmission. Darker pixels will have a larger Z value, a thicker print, and less light transmission.”) Finally, he generated a border and any other geometry required to close the mesh.
Once the STL files were exported to Blender, he used a Stratasys Objet30 Pro 3D printer and VeroGray material. “This precision [of the SLA 3D printer] is needed in order to faithfully reproduce the original image,” said Jensen. “In the lab we do have an FDM printer (the Dimension Elite). After some experience with the limitations of the process and some early tests with how the material transmits light, I decided against using this process. I needed to print features that were as small as 0.2mm across. I also decided that the slice thickness was too large to allow enough distinct brightness levels. This limits how accurately the print can reproduce subtle variations in contrast from the original image.” He added that for simpler photographs with high contrast and large features, however, an FDM 3D printer could do the job.
The mostly nature-themed photographs that Jensen selected, which include a desert scene, a wildflower, and an inside-view of a hot air balloon, translate beautifully into 3D printed lithophanes, revealing a surprising amount of realism and detail when placed over a light.
There are currently online tutorials for recreating your own 3D printed lithophanes, and because the results are quite realistic, you could choose just about any photograph you want, including family portraits. As for Jensen, he said that there are still some interesting aspects in regards to the 3D printing technique that he would like to explore at some point in the future. “The prints look best when you turn out all the lights in the room, but that's kind of inconvenient. I'd want to experiment with different materials and colors to see if I can reduce that need,” he said. “Another idea I had was to vary the thickness on both the front and back of the print, but offset each pixel randomly. The purpose would be to make it impossible to see what the image actually is until it's been properly illuminated.”
Finally, if there’s one thing I learned through this story (aside from an 19th century art form and a new method for 3D printing photos), it’s that on today of all days, Star Wars truly is an inescapable force.
Posted in 3D Printing Application
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