Forget holograms you can only stare at—researchers at the Public University of Navarra (UPNA) in Pamplona, Spain have built a 3D display you can actually manipulate..
In a breakthrough that literally blurs the line between the virtual and the tangible, a seven-member team, led by Dr. Elodie Bouzbib, has developed a volumetric display you can reach into. The technology relies on a surprisingly simple setup: A sheet of thin plastic bands, laid side by side, like flat ribbons of pasta, and suspended within a lightweight frame, or diffuser. The magic happens when the diffuser moves up and down at such high speeds that the motion becomes invisible to the human eye. The plastic bands flap, or oscillate, up and down and when the images cast from a projector hits them, a 3D image comes to life.
But this system does more. The elastic ribbons can also correlate touch. When a person presses on or drags a finger across the image, the system detects the touch and shifts the 3D image accordingly. Instead of just looking at a virtual object, users can utilize reach-through hand techniques, such as touching, grasping, pinching in and out, turning around, pushing, and swiping, to add a tactile dimension to a digital experience that once seemed confined to science fiction.
The team recently posted a 14-minute explanatory video on YouTube, and also detailed their complex research in a 17-page paper, “FlexiVol: a Volumetric Display with an Elastic Diffuser to Enable Reach-Through Interaction,” that was posted on the open-access archive HAL open science.
“Volumetric displays render true 3D and can provide most of the visual cues that we perceive from the real world. However, with current technologies, users cannot reach inside the display volume to directly interact with virtual objects as they would do in real life. Their diffusers are most often rigid, which causes safety hazards when reaching through; and interaction techniques are thus performed indirectly using a 3D mouse or a keyboard. FlexiVol’s concept is based on modifying metric displays with an elastic optical diffuser to enable users to insert their hand within the rendering volume and directly interact with spatially overlapped true 3D graphics. The true 3D graphics and user hand provide coherent focus accommodation, which allows for enhanced depth perception. The interaction with the rendered graphics is direct, the user can grab an object to move and rotate it.”
The team was scheduled to present its work at the CHI 2025 conference in Yokohama, Japan, from April 27-May 1. The other researchers include Iosune Sarasate, Unai Fernández, Manuel López-Amo, Iván Fernández, Iñigo Ezcurdia and Asier Marzo.
A goal of the project is to revolutionize the way engineers, artists, architects and other professionals design and interact with complex objects, instead of studying flat renderings on a screen or building expensive prototypes. They could soon physically manipulate 3D images in real time, to perhaps tweak the curve of a car hood, or adjust the fit of an engine, or experiment with new components on the fly. The technology could dramatically speed up design cycles, encourage more creativity and make the leap from idea to finished product a whole lot smoother.
During testing, the team experimented with different types of plastics and other material, like a projection screen, to gauge which would work best. The samples were subject to stretching, and also tested to determine which reflected the best image. Even the sounds emitted by the strips were tested because frequency plays a role in image distortion. An elastic band was chosen based on its resiliency, reflective and sound properties and other criteria.
The 3D image is achieved through a series of planes that appear to be a single image. With a high speed camera, the planes become obvious, like rings that capture the outline of an image at different levels. These slices blend together to form the entire image.
“All together they render the full object,” Dr. Bouzbib said. She explained the diagram of a 3D rabbit. “Thanks to high-speed video capture, we can see here the rabbit appearing as slices . . . at a higher speed, and with the persistence of vision, we hence find our rabbit again.”
In testing, they recruited 18 participants, who filled out a questionnaire at the end of their experience. The participants tested the reach-through technology versus using a 3D mouse, in terms of manipulation of the image.
“Reach through showed significantly better results . . . the mental workload was significantly higher with the 3D mouse, as per the temporal demand. Effort, performance, and frustration were also perceived as worse with the 3D mouse. More globally, the reach-through modality was significantly less cognitively demanding than the 3D mouse. Regarding qualitative feedback, more than half of the participants spontaneously mentioned that it was easier and more natural to interact with the fingers. They mentioned how it was more spontaneous, more intuitive, and that we are more used to interacting with our hands.”
In a press release from the team, Dr. Marzo, the lead researcher, said, “We are used to direct interaction with our phones where we tap a button or drag a document directly with our fingers on the screen, it is natural and intuitive for humans. This project enables us to use this natural interaction with 3D graphics to leverage our innate abilities of 3D vision and manipulation.”
Dr. Bouzbib mentioned that the team is working on ways to add improvements, such as by adding haptic technologies, like focused ultrasound, which can travel through the elastic fabric and create a tactile stimuli on the fingertip as it interacts with the 3D image. Another possible improvement would be to sew conductive thread through the elastic material to produce electromagnetic feedback. Also, the team is looking at supersizing the entire display.
The art world is also taking advantage of 3D in a big way as more galleries now feature 3D exhibitions, with images beamed from projectors onto strings hanging from ceilings, and other displays.
