Mixed reality catches up with construction sites

With mixed reality, it is possible to superimpose the digital model on the work in progress. This is a valuable aid for inspections, but not only.

Mixed reality is a display technology that combines real elements with virtual elements. It is used with a tablet or, more immersively, with special glasses. On a building site, for example, the user sees elements of the digital model superimposed on the existing structure. Mixed reality thus makes it possible to project what is planned in the design phase onto what is carried out in the execution phase. The benefits of this technology lie in this confrontation, which is beginning to interest companies such as Spie.

“Our first use of mixed reality is to check the installations,” explains Anna Truong, innovation manager in Spie’s service sector department. At a glance, we can see whether the ducts, cable trays, electrical cabinets, etc. are in the right place, whether the reservations were correctly made during the structural work, and this with an impressive saving of time. Checking 1000 reservations in a building in the traditional way requires, for example, 83 hours for an operator. With the helmet, it takes just over an hour!”

The company, which specialises in electrical, mechanical and HVAC engineering, energy and communication networks, has been studying this solution for three years in partnership with NEXT-BIM, the developer of the solution. It has been using mixed reality headsets in an operational manner since this year, and will soon have five packs and should acquire around twenty in 2021 to cover all its sites in France. It is not the only one.

Mixed reality is also used by Vinci Construction Suisse (VCS), for example, on the vast renovation site at Geneva airport, to monitor the installation of HVAC systems.
“Mixed reality is also used by Vinci Construction Suisse (VCS), for example, on the vast renovation site at Geneva airport, to check the installation of HVAC systems. Mixed reality also allows us to project ourselves into the empty building,” continues Anna Truong. Superimposing the model on the space allows us to preview the equipment to be installed. It is an aid to the preparation of the site. Actually, it is all the more useful in the case of renovation, since it is possible to check that the equipment planned in the model will have the necessary space in reality.

Finally, mixed reality can also be used during the operational phase , as confirmed by Frank Aboulker, director of NEXT-BIM. “On the CentraleSupélec site, Bouygues Energies & Services operators use it to guide their work. By superimposing the digital model on the existing building, they are able to visualise precisely the equipment to be installed through the walls and ceilings.” “Mixed reality also allows us to project ourselves into the empty building, continues Anna Truong. Superimposing the model on the space allows us to preview the equipment to be installed. It helps to prepare the site. This is particularly useful in renovation projects, since it is possible to check that the equipment planned in the model will have the necessary space in reality.” Ultimately, mixed reality can also be used during the operational phase, as confirmed by Frank Aboulker, director of NEXT-BIM. “On the CentraleSupélec site, Bouygues Energies & Services operators use it to guide their work. By superimposing the digital model on the existing building, they are able to visualise precisely the equipment to be installed through the walls and ceilings.”

Mixed reality, A technology that is still rare and therefore expensive

Today, mixed reality on site is based on Microsoft’s Hololens 2 glasses. No other product is yet available on the market. In fact, the glasses are a device – a helmet – with a screen visor associated with a central computer unit positioned at the back of the head.

A version integrated with a construction helmet, the Trimble XR10, is also available. “The experience with the XR10 is exceptional because its weight is well distributed. And the second Hololens is better calibrated. With the first one, you had a headache after half an hour”, says Rémi Visière, R&D Director at GA Smart Building, a builder and developer in the tertiary sector, which has been experimenting with mixed reality for several years for monitoring and preliminary surveys.

But to date, this operator has not generalised the use of the helmet. “The level of acceptability of the technology is not yet optimal,” concedes the engineer. Many of our employees find the headset fragile and fear breakage. However, the headset, earphones and Microsoft software suite cost 5,000 euros.” In fact, the headset costs five times the price of a tablet, with which it is also possible to do mixed reality. Even if the glasses are more immersive and allow you to keep your hands free. In addition to the cost of the hardware, there is also the cost of a software solution developed for the world of construction. “There are no off-the-shelf products or standardised programmes yet. Everyone has to develop a solution on their own” ddeplores Rémi Visière. The NEXT-BIM headset costs 3,000 euros per licence, which is probably the most advanced solution on the site at the moment. The company has developed technologies that allow it to compress IFC models so that they can be integrated into the helmet’s memory. “We achieve compression ratios of up to a factor of 22. We manage to reduce the file size of a 4.4 GB model to 200 MB”, illustrates Frank Aboulker.

Compression of IFC mock-ups

Thus, in order to have the elements of the model available in real time, it is no longer necessary to have Internet access, which is often difficult on building sites where the networks are sometimes non-existent.

The other advantage of this technology is that it does not require “beacons” on the walls and ceilings to wedge the images from the digital model onto the already built elements. There is a wedging technology that requires QR codes to be placed on the walls. The problem with this kind of solution is that there are not always walls to put them on…

“Our technology is based on the real environment, with some vertical elements, to set the digital model (in the visor). In the future, we will even use geometric points for new construction sites”, continues Frank Aboulker.

Hololens 2 has another advantage over the previous version. It is possible to synchronise “passenger” headsets with a “pilot” headset. Thus, visitors can accompany an operator and visualise the mixed environment where the latter is located. NEXT-BIM also offers a “passenger” licence at 1500 euros. These prices are still high, but it is likely that with time, mixed reality will become more accessible, as has been the case for every new technology.