Promises kept! After five years of work and the fire at Notre-Dame de Paris Cathedral on April 15, 2019, the building reopened to the faithful and the public on November 7, 2024. Much was said and paid tribute to the Companions, these hundreds of workers and supervisors who worked tirelessly on the site. Less mentioned is the contribution of digital technologies which were for many the keystone of their work. 20 Minutes questioned Nicolas Mangon, vice-president of architecture, engineering and construction strategy at software manufacturer Autodesk, who was present from the first hour.
What is Autodesk’s mission?
Autodesk is an American company based in San Francisco, which has existed for forty-two years. We develop software for three different industries. First of all that of architecture, engineering and construction. Then for those in the manufacturing industry where we develop bicycles with Decathlon, agricultural tractors, or parts to lighten certain parts of Airbus planes. Finally, those of films, like Avatarand video games that create special effects with our software.
Would it have been possible to rebuild Notre-Dame without your software?
Everything would have been possible, no doubt. Where our contribution has, I imagine, been valuable is in saving time. The objective of completing the work in 2024 might not have been achieved.
What was the working basis for the reconstruction site?
There was no drawing or reference plan for Notre-Dame. Surprisingly, there had been no documentation work on its design, its structure either. Just a few sketches here and there. To reproduce the cathedral identically, it was necessary to know after the fire what “identical” was…
Luckily, the Ministry of Culture, which owns the building, had commissioned the company Art Graphique et Patrimoine a few years before the disaster, which uses our software to document Notre-Dame in 3D.
This work was carried out using laser stations called theodolites. Placed in countless locations around the building, with a range of up to approximately 30 meters, they carried out scans using billions of points, called “point clouds”. Once inserted into our software, these readings were then transformed into 3D reconstructions that can be manipulated and animated, a bit like a 360° photo.
Scans before the fire, but also after…
After the disaster, Philippe Villeneuve, the architect of Historical Monuments at the head of the cathedral restoration project, asked us again to carry out a scan of the rubble.
The goal this time was to map the extent of the damage. Firstly, to find out where things had gone as part of the investigation. But also, when the problem of the stability of the arches appeared, to determine the exact nature of the difficulties that had to be faced. And know how to solve them.
What was your contribution?
At first there was panic on board! But this phase was essential to communicate with the teams who were going to try to stabilize the building. Without this technology to design a stabilization strategy, it would have been much more complicated. Initiatives would undoubtedly have been taken, at the risk of accidents and collapses.
Then, lots of drawings were made from our point clouds. We were able to model “intelligent” objects (to be manipulated on a computer), such as walls, pillars, etc. and create a complete digital model of the cathedral. This was crucial for all the trades involved. Because thanks to this model, it then became possible to model each brick, each wall, to cut, to associate, to determine the masses…
Our articles on Notre-Dame de Paris
We imagine that the reconstruction of Eugène Viollet-le-Duc’s Flèche benefited from your expertise…
From its 3D model, two things were possible. First, separate virtually all the elements of the construction of the Arrow so that they can then be assembled, like with an Ikea assembly plan. Furthermore, we were able to digitally simulate its wind resistance and determine its necessary resistance by simulating storms, those that occur every 10 years, 50 years, etc.
How has your software influenced the light now omnipresent in the building?
Our software made it possible to work on all the effects of light in order to highlight the brilliance of the cathedral day and night: knowing where to integrate lighting, with what intensity, what shadows, knowing if we wanted direct light or diffuse. And this, without having to go to the construction site. Everything could be prepared virtually, especially during Covid. Autodesk brought Notre-Dame to the computer screens of those who also worked on this project from their office!
It is said that all this has brought you nothing…
In addition to a significant financial donation made by Autodesk after the fire, we fully valued our participation in the form of sponsorship. In addition, we have donated our software to hundreds of companies involved. Thus, each worker could, if necessary, directly from their smartphone, access any area of the digitized cathedral.
Can our material heritage today do without these technologies?
Digital helps preserve memory. With the fighting in Syria or Ukraine, many buildings and monuments have been scanned. Without this work, it is impossible to recreate, redo when the time comes. It is important to capture world heritage digitally. It is the memory of men that is in question.
