Abstract
Abstract. 3D city models are increasingly being used to represent the complexity of today’s urban areas, as they aid in understanding how different aspects of a city can function. For instance, several municipalities and governmental organisations have constructed their 3D city models for various purposes. These 3D models, which are normally complex and contain semantics information, have typically been used for visualisation and visual analysis purposes. However, most of the available 3D models open datasets contain many geometric and topological errors, e.g., missing surfaces (holes), self-intersecting surfaces, duplicate vertices, etc. These errors prevent the datasets from being used for advanced applications such as 3D spatial analysis which requires valid datasets and topology to calculate its volume, detect surface orientation, area calculation, etc. Therefore, certain repairs must be done before taking these models into actual applications, and hole-filling (of missing surfaces) is an important one among them. Several studies on the topic of automatic repair of the 3D model have been conducted by various researchers, with different approaches have been developed. Thus, this paper describes a triangular mesh approach for automatically repair invalid (missing surfaces) 3D building model (LOD2). The developed approach demonstrates an ability to repair missing surfaces (with holes) in a 3D building model by reconstructing geometries of the holes of the affected model. The repaired model is validated and produced a closed-two manifold model.
Highlights
INTRODUCTION AND MOTIVATIONTo allow for the development of advanced applications, a 3D city model should describe the geometry and attributes of all the individual elements that are typically present in a city
Stoter et al 2020 stated that there is a need for implementing an automatic repair technique to handle these problems, and a 3D model should be validated and repaired before it can be further used (Ledoux, 2013, Biljecki et al 2016)
In addition to these existing repair methods and algorithms, most of the contemporary 3D model repair research and development has been focusing on the repairing of generic 3D models (LoD2), common geometric errors, and volume-based models
Summary
To allow for the development of advanced applications, a 3D city model should describe the geometry and attributes of all the individual elements that are typically present in a city. As highlighted by Stoter et al (2020) and Biljecki et al (2019), (2016), most of the available 3D city models open datasets contain many geometric and topological errors, e.g. duplicate vertices, missing surfaces, self-intersecting volumes, etc. For 3D models to be used as an input in most city simulation and modelling software, the models should be geometrically and topologically valid Often, these errors are not visible at the scale on which the datasets are visualised, and some users are unaware of the issue due to the models appear to be valid in the software viewer. Validation of the 3D models geometry and the detection of the errors can be achieved through several tools such as Val3Dity (Biljecki et al, 2019), and CityDoctor (Wagner et al, 2013) These validators can validate CityGML datasets regarding their semantic and geometrical correctness or regarding their geometric-topological consistency. Stoter et al 2020 stated that there is a need for implementing an automatic repair technique to handle these problems, and a 3D model should be validated and repaired before it can be further used (Ledoux, 2013, Biljecki et al 2016)
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