A team of researchers at the Public University of Navarra (UPNA) in Spain have succeeded in displaying three-dimensional graphics in mid-air that can be manipulated with the hands.
Doctor Elodie Bouzbib, from Public University of Navarra (UPNA), together with Iosune Sarasate, Unai Fernández, Manuel López-Amo, Iván Fernández, Iñigo Ezcurdia and Asier Marzo (the latter two, members of the Institute of Smart Cities) have found a way to interact with 3D graphics, allowing users to grasp and manipulate virtual objects naturally.
"What we see in films and call holograms are typically volumetric displays," says Bouzbib, the first author of the work. "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. They are particularly interesting as they allow for the 'come-and-interact' paradigm, meaning that the users simply approach a device and start using it."
"Commercial prototypes of volumetric displays already exist, such as those from Voxon Photonics or Brightvox, but none allow for direct interaction with the holograms," the team points out. Asier Marzo, the lead researcher, comments that direct interaction means "being able to insert our hands to grab and drag virtual objects." He adds: "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. This project enables us to use this natural interaction with 3D graphics to leverage our innate abilities of 3D vision and manipulation."
This research is within the InteVol project, led by UPNA and funded by the European Research Council (ERC), which funds research within the European Union.
How these holograms work and practical applications
Volumetric displays have a fast oscillating sheet called a diffuser, images are projected synchronously at high speed (2,880 images per second). Thanks to the persistence of vision, the images projected onto the diffuser at different heights are perceived as a complete volume. “The problem,” notes the research team, “is that the diffuser is usually rigid, and if it comes into contact with our hand while oscillating, it may break or cause injury.” To address this, the team has 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,” adds Bouzbib.
This 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,” they illustrate.
Two people observing a 3D skull. One of them is touching the eye hole.
“Displays such as screens and mobile devices are present in our lives for working, learning, or entertainment. Having three-dimensional graphics that can be directly manipulated has applications in education — for instance, visualising and assembling the parts of an engine. Moreover, multiple users can interact collaboratively without the need for virtual reality headsets. These displays could be particularly useful in museums, for example, where visitors can simply approach and interact with the content,” explains the research team.