The Bronze Head of Lucius Cornelius Pusio as 3D Model
The bronze head of Pusio, housed in the Museo Nazionale Romano – Terme di Diocleziano in Rome, is one of the most significant archaeological finds connected to the Roman military site of Novaesium (modern-day Neuss). It is the oldest known portrait of a resident of Neuss and even the Lower Rhine region. The head was discovered in 1892 on the grounds of the Palazzo Campanari in Rome. A bronze inscription plate found alongside it identifies the figure as Lucius Cornelius Pusio, a legate (commander) of the Legio XVI Gallica, which was stationed in Neuss from 42 to 69 AD. The head was likely originally part of a slightly larger-than-life-sized statue, which M. Vibrius Marcellus, a centurion of the XVI Legion, dedicated to his former commander in the late 60s AD.
To make the portrait of the legate permanently accessible to a wider audience in Germany, the Clemens Sels Museum Neuss, in collaboration with the Archaeological Institute of the University of Cologne, adopted an innovative method for documenting and presenting archaeological finds. A contactless, three-dimensional virtual model of the head was created, which was then printed in a 1:1 scale and will serve as the basis for further digital reconstructions and animations in the future.
The bronze head of Lucius Cornelius Pusio in the Museo Nazionale Romano in Rome is one of the most important archaeological finds associated with Roman Novaesium.
The bust represents the oldest known portrait of a resident of Neuss and the Roman province of Lower Germania.
The Process of Creating the 3D Model
The three-dimensional capture of the bronze head presented several challenges. The head was firmly mounted on a pedestal in the Diocletian Baths and positioned close to a wall, which made it difficult to accurately scan the back of the head. Additionally, it was illuminated by a spotlight from the side, which created shadows on the left side of the head.
Two different methods were used to create the 3D model. First, a 3D handheld scanner was used to capture the surface of the head point by point with a laser. This work was carried out by the company Scandric 3D SOLUTIONS from Bochum. The filtered 3D point cloud generated by the handheld scanner was then converted into a surface model (mesh), where individual points were meshed into small triangular surfaces forming a three-dimensional body. The surface model was then cleaned, given a wall thickness, and completed into a watertight volumetric model by filling any gaps. A photogrammetry software was then used to project the texture captured by a camera onto the volumetric model.
For the photogrammetric 3D modeling, the bronze head was photographed from various positions using a Canon EOS 700D DSLR camera and a Samsung SM-A515F smartphone. Efforts were made to ensure that neighboring photos had large overlapping areas. However, the insufficient lighting in the Museo Nazionale posed a challenge, particularly as flash photography had to be avoided to prevent reflections on the bronze surface.
The image data was then processed by the Cartography and 3D City Model department of Neuss Surveying (LVN), where it was used to generate a 3D model. The software automatically identified the relative position and orientation of each photo based on the overlaps with other images. The software ContextCapture by Bentley was able to utilize 728 out of the 832 captured photos (92%), calculating over 30,359 3D points, which were then meshed into triangles. High-resolution textures were then mapped onto these individual triangles, resulting in a 3D representation of the original with over 11.5 gigapixels.
The 3D Printing and Presentation
Initially, the plan was to print the 3D model in monochrome and then hand-paint it to match the original, but this idea was abandoned partly due to cost reasons. Instead, a full-color 3D printing method was used. However, this required remodeling the generated 3D model, as the uneven lighting in the museum had caused shadow effects in the textures. The shadowed areas had to be painstakingly brightened on a computer before printing.
The 3D printing was carried out by the company Marketiger from Eindhoven using a Mimaki full color 3D printer. A significant challenge was the size of the object and the requirement that the head be printed as a hollow structure, just like the original. To achieve this, a water-soluble support structure was printed inside the model, around which the material for the final object was built up. After printing, the support material was washed out and dissolved.
In the future, the head of Lucius Cornelius Pusio is expected to be animated and displayed in the new permanent exhibition on Roman history at the Clemens Sels Museum Neuss. This exhibition will be set up after the museum completes its renovation work, which became necessary after a heavy rainstorm on May 20, 2022, flooded the museum’s basement.