[A research team from Public University of Navarra (UPNA) in Spain has developed a 3D hologram system likely to evoke greater presence because it allows users to manipulate projected objects not with a 3D mouse but directly with their hands. The system is described in the story below from The Debrief, where the original version includes a second image and a 2:31 minute video (also available on YouTube). For more information, a longer video, and a link to the team’s open source paper, see the UPNA website. –Matthew]

Video: Interactive 3D Hologram Allows Users to Manipulate Virtual Objects with Their Hands

By Christopher Plain
April 11, 2025

A team of researchers has built the first-ever interactive three-dimensional (3D) hologram, FlexiVol, that allows users to manipulate virtual objects with their hands. Although some commercially available interactive holograms already exist, FlexiVol is the first to allow users to manually interact directly with virtual objects projected into thin air rather than using an external controller.

“We are quite excited about [FlexiVol’s] combination of volumetric displays (to provide natural understanding of 3D graphics) and direct interaction (to allow for intuitive manipulation of 3D objects),” lead researcher Azier Marzo of the Institute of Smart Cities told The Debrief.

The team is currently working on several hardware and software upgrades designed to improve the resolution and functionality of their interactive 3D hologram system. They also hope to integrate tactile sensation feedback so users can “feel” the objects.

According to Marzo, the goal is to create an interactive artistic installation “so that people can experience this combination firsthand and start a more end-user approach to design target applications.”

Interactive 3D Holograms Are More ‘Natural and Intuitive’

Since the first 3D hologram was created in the 1940s, engineers have looked for ways to improve the quality of the images while exploring potential commercial applications. For example, integrating the technology onto portable devices has gone from a concept to a smartphone capable of generating 3D holograms within just a few years.

Efforts to find practical uses for 3D holograms have also resulted in the first-ever augmented reality 3D holographic headset and a realistic 3D holographic zoo that lets visitors “walk” with the dinosaurs. Still, while technologies to improve the resolution of holograms continue to advance, directly interacting with virtual objects has mostly remained in the realm of science fiction.

“We are used to direct interaction with our phones, where we tap a button or drag a document directly with our finger on the screen – it is natural and intuitive for humans,” Marzo explained. “[That means] being able to insert our hands to grab and drag virtual objects.”

The desire to create this type of intuitive holographic display motivated Marzo and his fellow researchers to create FlexiVoo. Based on the team’s recently released video, they appear to have broken the 3D hologram interaction barrier by creating the world’s first interactive 3D holographic display.

Elastic Diffuser is the ‘Magic’ Component

Like all currently available volumetric displays, FlexiVol uses a fast-oscillating projection surface called a diffuser. Because the diffuser typically oscillates at a high speed, the images projected onto it appear as a complete volume. However, diffusers are generally rigid, so if someone tried to interact with them, it could cause serious injury.

To combat this limitation, the team, which included Marzo and Iñigo Ezcurdia of the Institute of Smart Cities, Doctor Elodie Bouzbib, from Public University of Navarra (UPNA), and Iosune Sarasate, Unai Fernández, Manuel López-Amo, Iván Fernández, explored several elastic diffuser options. After testing different materials to determine which possessed the best optical and mechanical properties, they settled on the final design seen in the video.

Because elastic materials deform when touched, the team employed image correction software to maintain image quality and resolution. Marzo told The Debrief that an improved version with higher-resolution cameras “that capture in synch with the strip oscillation so that the frame is captured when the strips are below the hand” should improve this significantly.

Planned Improvements Include Larger Size, Crisper Images & Tactile Sensations 

Along with higher-resolution cameras, the team is exploring other potential improvements to increase their system’s size, clarity, and functionality. According to Marzo, the most important step is increasing the size of the relatively small 19x19x8 cm display volume, which only allows users to use one hand, to accommodate larger, more complex holograms.

“We want to increase the volume to at least 1 square meter, mainly to study applications and artistic installations where various users collaborate,” Marzo told The Debrief.

Another limitation of the current design is that the user’s hand can only be inserted from the top. Marzo said the team wants to explore oscillating the strips from two sides “so that people can interact from the top, the sides, and perhaps from below.” They are also considering a new silicon composite with tiny spheres to make the strips lighter and more elastic.

Several times during the video, the 3D hologram becomes distorted when the hand touches the strips. The team leader said that planned improvements in the software should correct that. The team is also exploring using brighter projectors so FlexiVol can operate more effectively in regular lighting conditions.

Perhaps the most intriguing improvement under consideration is making the interactive aspects of the experience more realistic. According to Marzo, that includes potentially adding specialized feedback so that “when you grab or touch the holograms, you feel some tactile sensations on the contact points.”

Potential Applications and an Interactive Artistic Display

The team says several limitations in current technology still need to be overcome for finer control of 3D holograms. According to Marzo, hand-tracking technology still needs to improve to capture fine finger movements. This issue is even more challenging for FlexiVol since the elastic strips pass around the hand, “causing occlusions.”

“[Our system] can detect accurately pointing with the index finger, and pinching between thumb and index,” Marzo told The Debrief. “But we cannot detect subtle shifts between the fingers or small variations in the grip.”

When discussing potential applications, the team highlighted several intriguing possibilities. For example, FlexiVol could help students visualize and assemble the parts of an engine or other complex machinery. The team also suggested that multiple users could interact with the display at once without virtual headsets, opening up applications for museums and interactive marketing displays “where visitors can simply approach and interact with the content.”

Marzo told The Debrief that the team is working on an interactive artistic installation that will allow everyday individuals and engineers to explore an even wider range of potential uses that his team hasn’t even dreamed of yet.

“We have some applications in mind,” the researcher said, “but we are sure that users will provide another perspective.”

The FlexiVol will be presented at the CHI 2025 conference in Yokohama (Japan) between April 26th and May 1st. Over 4,000 researchers, including representatives from companies like Microsoft, Meta, Apple, and Adobe, are expected to attend this event. A video of the team’s results and the presentation is available on YouTube.