Work conducted by Universidad Pública de Navarra researchers has produced 3D graphics in mid-air that can be manipulated by a user’s hands. “What we see in films and call holograms are typically volumetric displays,” said first author Elodie Bouzbib. “These are graphics that appear in mid-air and can be viewed from various angles without the need for wearing virtual reality glasses. They are called true-3D graphics.” The displays, she said, “are particularly interesting as they allow for the ‘come-and-interact’ paradigm, meaning that the users simply approach a device and start using it.” A new approach to volumetric displays allows users to interact with 3D images. Courtesy of Universidad Pública de Navarra/Iñigo Ezcurdia. According to the researchers, commercial prototypes of volumetric displays already exist, such as those from Voxon Photonics and Brightvox Inc., but none currently allow for direct interaction. “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,” said lead researcher Asier Marzo. “This project enables us to use this natural interaction with 3D graphics to leverage our innate abilities of 3D vision and manipulation.” Volumetric displays have a fast oscillating sheet called a diffuser and images are projected synchronously at high speed (2880 images per second). The images projected onto the diffuser at different heights are perceived by human eyes as a complete volume. The problem with this, the researchers said, is that the diffuser is usually rigid and can cause injury or break if it comes into contact with a user’s hand. To address this, the team replaced the rigid diffuser with an elastic one after testing different materials for their optical and mechanical properties. The challenge is that “elastic materials deform and require image correction,” said Bouzbib. The innovation enables new ways to interact with 3D graphics, allowing users to grasp and manipulate virtual objects naturally. “For example, grasping a cube between the index finger and thumb to move and rotate it, or simulating walking legs on a surface using the index and ring fingers,” the researchers said. 3D graphics that can be directly manipulated could have applications in education. The researchers point out the example of visualizing and assembling the parts of an engine. Further, they said, multiple users can interact collaboratively without the need for virtual reality headsets. The team expects that the displays could find use in museums to allow visitors to simply approach and interact with the content. The work was conducted under the InteVol project, led by UPNA and funded by the European Research Council (ERC). The research will be presented at the CHI 2025 conference (https://hal.science/hal-04981007v1).