St. Ägidius in Schönfeld

Cultural heritage meets modern technology

3D Surveying

Team in action

martin schaich, Nicolas amanatidis, tuna Çapar, fatih sönmez, melanie nguyen

Basis for the model

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Camera-Photos
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Drone-Photos
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X-Citor Flight Photos
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Laserscans
St. Ägidius church (3D model)

Preface

The team of 3D monument preservation specialists from the ArcTron group of companies (Altenthann) used the latest airborne and terrestrial techniques for digital building surveys and 3D modeling for the inventory documentation, research and virtual representation of the small but particularly worth seeing Romanesque church from the 12th century. Die auf eigene Kosten von der ArcTron 3D realisierten Arbeiten wurden vor allem im Rahmen der  mehrmonatigen Fachpraktika von Melanie Nguyen (Bauforschung) und Fatih Sönmez (Multimedia) mit Unterstützung der verschiedenen Experten der ArcTron 3D  realisiert. Das Projekt entstand wesentlich im Zeitraum April to September 2020 due to the situation caused by the corona restrictions, which made alternative project ideas necessary for the internships. The church St. Ägidius in Schönfeld is a small monumental architectural "highlight" near the company headquarters. It is usually not easy for visitors to take a look inside. With this digital visualization, St. Ägidius' doors are now "open" to you. We would like to thank Mayor Herrmann (Altenthann) and Pastor Lehnen (Brennberg) for allowing us to document the church on site and present it digitally. We would like to thank the "German Foundation for Monument Protection" with Mr. Domagala for the short-term inclusion of our project in the "virtual" Open Monument Day on September 13th, 2020!                 

Digital 3-Dimensional Architectural Surveying

First, the area around Schönfeld could be explored with the company's own ultra-light paraglider trike and aerial photographs for a photogrammetric model of the area could be taken. This was followed by ground level drone footage of the church from many different perspectives as the basis for an exterior model. For the exact documentation of the building geometry, a total of 87 positions outside and in all interior rooms of the church were recorded with the terrestrial laser scanner. In addition, the interior of the nave could be photographed with a drone in order to better document, for example, vault areas that are difficult to access. Finally, in order to add detail and color information to the point clouds of the laser scans, all interiors of the church were precisely documented using “Structure-from-Motion” photogrammetry. With this photogrammetric technique, the rooms are photographed in such a way that a realistic model of the room geometry can be calculated with image series from many perspectives.

Fatih Sönmez taking photographs with a NIKON D850
Tuna Çapar performing a laser scan (RIEGL VZ400)
Martin Schaich flying a drone in the church interior (DJI P4 Pro V2)
The roof structure, generated in Reality Capture
3D model of the surrounding area generated using the photos from the flyover with an ultra-light aircraft

Data Processing and 3D Models

The 87 laser scans were first combined into a point cloud with more than 100 million measuring points, which describes the entire scanned interior and exterior geometry of the church as a coherent three-dimensional object. In the next step, the laser scans, together with all the interior and exterior photos of the church, were loaded into the "Reality Capture" program also offered by ArcTron, where they were first merged into a large point cloud with the help of control points. After further optimization of the point cloud, Finally, a high-resolution mesh was generated from it, and after a so-called “unwrapping" (cutting in 2D surfaces) of the surfaces with the photo textures, it was newly and fororealistically textured. Using the same procedure, the environment photos of the flight with an ultra-light paraglider trike were transformed into a 3D environment model of the small hamlet of Schönfeld.

Photogrammetric model of St. Ägidius, including the positions where drone footage was taken
Cross section generated using the point cloud from the laser scans
Floor plan generated using the point cloud from the laser scans
Interior with a view of the apse (photogrammetric model)
Interior with a view of the gallery (photogrammetric model)

Multimedia

3D Model of the church

Team in Action

f. sönmez, t. Çapar, M. nguyen, N. amanatidis, J. dittmer,
m. cahn von seelen

Remodelled church (exterior)
"X-ray" view of the model
"X-ray" view of the model's roof

Modelling

In order to make the 3D model more easily and interactively accessible to visitors on the Internet and to achieve better performance, a reduced, so-called “lowpoly” model was created. It can therefore also be used for other future projects in VR (Virtual Reality) and AR (Augmented Reality) applications or in games. 

First, the very high-resolution "HighPoly" model generated with "Reality Capture" was imported into 3D modeling software in order to be able to rebuild it there as a lower-resolution "LowPoly" model. For this purpose, views of the original model from different perspectives were orthogonally adjusted in such a way that they could be exactly remodeled. When remodeling, you first work out the rough elements and then gradually work out the smaller details. First of all, the external form of the church, consisting of the roof with turret, facade and entrance staircase, was modeled. In further steps, the interiors of the basement, main nave with gallery, attic and internal staircase were remodeled together with their objects. After the reconstruction of the individual interiors was finished, they were put together and finally integrated into the model of the outer shell.

Interior

UV mapping

For the texturing process of the new model, so-called UV maps were created from the individual 3D objects by cutting the surfaces of the objects into two-dimensional surfaces with auxiliary projections and placing them on a flat surface, which is referred to as "unwrapping" (straightening). During this process, it is very important to ensure that the surfaces are "unwrapped" in such a way that the new textures do not create distortions and overhangs on the object. The creation of UV maps is a very important intermediate step for the material and texture assignment after the finished object modeling. The more precise the UV mapping is, the better the texture "sits" on the object and the full texture resolution can be approximated.

Texturing

The texture is the surface or "skin" of an object, the quality and resolution of which decisively determines the image impression and the realism of the displayed object. High-resolution photo-realistic textures are therefore particularly important for monument objects! A surface can consist of different textures, such as rust or dust spots on a metal or wood surface, which make the object appear more realistic. There are two main types of textures, both of which were used in the St. Ägidius model: textures of external origin and so-called "baked" textures, which are taken from the original photogrammetric model. There are also "auxiliary textures", so-called "maps", which can be combined with the two main texture types, for example to create an impression of depth on a straight model surface. Such a "map" can be generated using depth information, which is either already contained in the scans, or created using image processing software.

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Baked textures of the interior
Baked normal map of the objects with UVs
Baked texture of the objects with UVs
St._Aegidius_UV_Diffuse
Baked textures of the interior

Material Assignment and PBR

With the help of so-called “PBR” (physically based rendering) materials, the texture can behave like metal, wood, plastic, glass, stone, etc. when exposed to light. In addition, there can be several materials on an object, which can react differently to the incidence of light depending on the appropriate settings. Various 3D platforms and game "engines" also make it possible to combine "auxiliary textures" such as normal maps with the texture in order to bring it closer to reality or the desired look.

Simply visit our interactive 3D model for a small photo-realistic "journey" around the building and a visit to the otherwise inaccessible interior!  

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