On April 15, 2019, the world watched as one of the most iconic buildings in the world, the Notre Dame Cathedral in Paris, nearly burned to the ground. A small fire had broken out in an attic early in the evening. Within minutes, the entire timber-framed roof and central spire were engulfed in flame. Staff rushed to rescue the countless works of art from the cathedral as more than 400 firefighters fought the blaze. The cathedral was still standing when the night ended, but this architectural treasure visited by millions every year, a UNESCO World Heritage Site, was irrevocably damaged by the disaster.
And so began the slow process to rebuild, a process that continues today. There has been much discussion about how to rebuild Notre Dame—whether it should be recreated as it was or modernized. There are varying opinions about whether to use wood, steel, or another material entirely. And there’s a lot of talk about how to keep it safe from future catastrophes.
These questions have no easy answers, but a new set of digital tools and approaches are available to help architects, engineers, and officials as they proceed forward. A 3D scan of the cathedral started by Art Graphique & Patrimoine (AGP) in 2010 enables them to see, in the most minute detail, the cathedral as it was before the fire. Scans by Leica give them additional perspectives as TruView models. And they have the power of Building Information Modeling (BIM) tools like Revit that enable them to explore both the old design and new possibilities in powerful and immersive ways, then simulate and interrogate those models, and move forward with full understanding of the impact of every choice they make.
These efforts are part of a larger movement among those who work in the fields of architecture and construction to digitize and preserve historic heritage sites and objects around the world. Using reality capture technologies and other approaches, those involved can document sites as they are, preserve them in digital form for generations to come, seek to understand them more deeply, and make those models and renderings accessible in ways that were never possible before.
Protect, Rebuild, Improve
“Our spaces are at risk,” Nicolas Mangon says, VP of AEC Strategy & Marketing at Autodesk. He opened the AEC Keynote at AU Las Vegas 2019 with a discussion of the Notre Dame fire and the importance of preservation. “The United Nations forecasts that we currently have more than $4 trillion of at-risk assets across the globe. Some of this risk is due to natural disasters that have increased dramatically in the last 20 years. Aging infrastructures make these disasters worse.”
“Disasters will continue to happen, and our industry is a first responder,” Mangon continued. “Technology is a tool that can help us protect, rebuild, and improve. Digitizing places like heritage sites is vital to better respond when there is a tragedy.”
“If AGP had not scanned Notre Dame, we would have nothing to help us rebuild,” Mangon said. “Today Autodesk and AGP are teaming up to develop a complete BIM model in Revit based on the scans. This model will be made available to all involved in the effort to reconstruct the cathedral.”
Capturing Reality, Capturing History
“Architects have to capture reality all the time,” says Paul Aubin, author and architectural consultant. “We used to do it with a tape measure and a yellow notepad. It’s more efficient to use a device.”
Today, that means terrestrial laser scanning, mobile laser scanning, photogrammetry—technologies that capture data about the real world that can then be fed into a tool like Autodesk ReCap to create a digital model of reality that’s accurate down to the millimeter.
Aubin and others are using these technologies to capture the Italian town of Volterra as part of a series of workshops organized by the Volterra-Detroit Foundation, a nonprofit collaboration between alumni and friends of the University of Detroit Mercy in the U.S. and the city of Volterra in Italy.
Situated near Florence in Italy’s province of Pisa, Volterra is of importance and interest because it has been continuously inhabited for at least the last 3,000 years. That means it’s home to a multitude of architectural legacies, from Etruscan and Roman to Medieval and Renaissance. Some are ruins, but others are still in active use—albeit with centuries of evolution and adaptive reuse.
Aubin has been part of the scanning effort since the beginning. “These ruins are layered on top of each other,” he said when he and his team sat down with us at AU Las Vegas 2019. “It’s interesting to see these layers of history. And there’s new stuff being discovered every day.”
“In Volterra, they have issues with earthquakes,” says Matthew Bainbridge, a reality capture specialist with Civil & Environmental Consultants in West Virginia. “A lot of these ruins are being destroyed over time. So this is a chance to capture it now and preserve it so that people can visit it years from now.”
“What we’re really trying to do with this data is make it available in a platform so that people can access and visit heritage sites virtually,” says Aubin. “Whether that’s in a web browser or using a VR headset or 3D printing, there’s lot of ways for people to interact to further their understanding of these important sites.”
Paul Aubin and his colleagues talk about their work to digitally capture historic structures at the ancient city of Volterra, Italy.
Sketching with BIM
In addition to reality capture, there’s another approach to this kind of historical preservation, one that relies as much on human imagination as on data. It involves bringing what data is available into a BIM platform like Autodesk Revit, then using traditional design practices to recreate structures that might no longer exist. Andrew Milburn, an architect with Godwin Austen Johnson in Dubai, is a leading proponent of this approach. He also sat down for a conversation on the subject at AU Las Vegas 2019.
“I like to use BIM tools to explore ideas,” Milburn says. “Particularly the way we as human beings have built things at different times and places. [The goal is to] understand ourselves better by seeing how human beings have lived, how they’ve built their cities, their houses, and their religious buildings.”
“I call Revit my BIM pencil, and I think of the digital tools as pencils with superpowers.”—Andrew Milburn, Architect, Godwin Austen Johnson
For Milburn, the process started in 2015, when he got involved with Project Soane, a competition to create a BIM model of the Bank of England as it was 200 years ago. “The Bank of England was demolished in the 1930s and rebuilt,” Milburn says. “So the Sir John Soane design, which was a pretty famous piece of architecture, was lost. The idea was to recreate this in Revit.”
When the Notre Dame fire happened, Milburn thought there was the potential to use the same approach. “I set off to see what kind of a model of Notre Dame I could create in a weekend. I did a massing study model of Notre Dame, did a blog post, and shared it on LinkedIn. People got very interested and more people have gotten involved.”
“I’ve been interested in impressionistic sketching for a long time, how to express something quickly,” he says. “The idea of the measured drawing has been a standard first-year architecture project for decades. How would you do that with BIM?”
Unlike reality capture with digital devices, it’s “not so much about doing a perfect model. It’s more about the learning experience.” It provides a complementary effort to traditional reality capture.
Andrew Milburn explains his use of BIM to create digital models for exploring, understanding, and preserving architectural history.
Milburn and others continue to collaboratively refine and improve their model of Notre Dame using Revit and BIM 360, even without having access to the AGP point cloud data. Milburn shares regular updates on his blog, along with other thoughts about BIM.
Architects, engineers, and contractors spend most of their time focused on what they’ll build next. And with a growing global population, people certainly need new homes, offices, and buildings.
But protecting, rebuilding, and improving the structures already in place is just as important. Because whether you’re talking about the pyramids of Egypt, the bridges of Pittsburgh, or homes in Puerto Rico, all structures are temporary. Rock crumbles, wood rots, steel bends. And the architectural icons we think of as having been around “forever” in reality have only been lucky enough to make it for a few thousand years. “Technology can help us protect and rebuild our spaces. It can help us improve them, too,” says Nicolas Mangon. “Protecting, rebuilding, and improving is necessary for our future and the built environment.”
But digitally preserving and recreating important historic sites brings its own rewards, both for architects as professionals, as well as for our broader culture. As Andrew Milburn said, “To decide where we want to go as a society, where we want the digital tools to take us, we have to know where we’re coming from.”