3D modeling of objects such as statues, moldings or ornaments, answers to a need of documentation and analysis in the field of cultural heritage. Several sensors based on different technologies are used to obtain information on the geometry of an object in form of point clouds: laser scanners, digital cameras or more recently RGB-D cameras. Among them, the recent Kinect v2 sensor looks promising and therefore its use has been studied in this paper. The aim of this paper is to compare two methodologies for 3D models acquisition: photogrammetry-based models and models obtained using a RGB-D camera. Since the quality of the meshed models is obviously correlated to the quality of the point cloud, the result will be more or less faithful to reality. To quantify this reliability, several comparisons to a reference model have been carried out. Regarding the results of the comparisons, we will be able to conclude about the strengths and weaknesses of photogrammetry and RGB-D cameras for 3D modeling of complex objects.
Several recording techniques are used together in Cultural Heritage Documentation projects. The main purpose of the
documentation and conservation works is usually to generate geometric and photorealistic 3D models for both accurate
reconstruction and visualization purposes. The recording approach discussed in this paper is based on the combination of
photogrammetric dense matching and Terrestrial Laser Scanning (TLS) techniques. Both techniques have pros and cons,
and criteria as geometry, texture, accuracy, resolution, recording and processing time are often compared.
TLS techniques (time of flight or phase shift systems) are often used for the recording of large and complex objects or
sites. Point cloud generation from images by dense stereo or multi-image matching can be used as an alternative or a
complementary method to TLS. Compared to TLS, the photogrammetric solution is a low cost one as the acquisition
system is limited to a digital camera and a few accessories only. Indeed, the stereo matching process offers a cheap,
flexible and accurate solution to get 3D point clouds and textured models. The calibration of the camera allows the
processing of distortion free images, accurate orientation of the images, and matching at the subpixel level. The main
advantage of this photogrammetric methodology is to get at the same time a point cloud (the resolution depends on the
size of the pixel on the object), and therefore an accurate meshed object with its texture. After the matching and
processing steps, we can use the resulting data in much the same way as a TLS point cloud, but with really better raster
information for textures. The paper will address the automation of recording and processing steps, the assessment of the
results, and the deliverables (e.g. PDF-3D files). Visualization aspects of the final 3D models are presented. Two case
studies with merged photogrammetric and TLS data are finally presented:
- The Gallo-roman Theatre of Mandeure (France);
- The Medieval Fortress of Châtel-sur-Moselle (France), where a network of underground galleries and vaults has been
ARPENTEUR is a web application for digital photogrammetry mainly dedicated to architecture. ARPENTEUR has been developed since 1998 by two French research teams: the 'Photogrammetry and Geomatics' group of ENSAIS-LERGEC's laboratory and the MAP-gamsau CNRS laboratory located in the school of Architecture of Marseille. The software package is a web based tool since photogrammetric concepts are embedded in Web technology and Java programming language. The aim of this project is to propose a photogrammetric software package and 3D modeling methods available on the Internet as applets through a simple browser. The use of Java and the Web platform is ful of advantages. Distributing software on any platform, at any pace connected to Internet is of course very promising. The updating is done directly on the server and the user always works with the latest release installed on the server. Three years ago the first prototype of ARPENTEUR was based on the Java Development Kit at the time only available for some browsers. Nowadays, we are working with the JDK 1.3 plug-in enriched by Java Advancing Imaging library.