Details

Autor(en) / Beteiligte

• Padsala, Rushikesh
• Banerjee, Sanghmitra
• Belayneh, Tamrat
• Santhanavanich, Thunyathep
• Coors, Volker
• Muñoz-Pandiella, Imanol
• Moreno, Aitor
• Jaspe-Villanueva, Alberto
• Posada, Jorge

Titel

Conceptualizing I3S encoding for OGC CityGML 3.0 Building Model

Ist Teil von

• Proceedings of the 28th International ACM Conference on 3D Web Technology, 2023, p.1-11

Ort / Verlag

New York, NY, USA: ACM

Erscheinungsjahr

2023

Link zum Volltext

Quelle

ACM Digital Library

Beschreibungen/Notizen

• Web-based visualization of large-scale 3D city models and urban digital twins is essential for various applications, such as urban planning, infrastructure management, environmental analysis, and public participation. The widely used OGC CityGML standard to store semantically rich large-scale 3D city models is not well suited for web-based visualization due to its GML encoding. The conversion of CityGML-based 3D city models to web-friendly formats like 3D Tiles and I3S often leads to data loss due to the inability of such streaming formats in preserving hierarchical organization and semantic relationships inherent in the CityGML data model. Additionally, inconsistencies may arise during maintenance or updates primarily due to the secondary usage of these formats rather than being used as a direct encoding. Therefore, in this paper, we present the concept of using I3S as a direct encoding for CityGML 3.0. The recently released CityGML 3.0 version distinctly separates its conceptual data model from the data encoding. This significant change enables the provision of additional encoding specifications beyond GML, a capability that was not possible in the previous version, CityGML 2.0. This opens a new paradigm where CityGML payloads could be optimized using existing 3D encodings such as OGCs Indexed 3D Scene Layers (I3S) standard, designed to support 3D streaming and distribution of large volumes of 3D content through a combination of Level of Detail (LoD) and selection criteria. The advantage of CityGML I3S encoding is that it combines a semantically rich 3D city model with a bounding volume hierarchy (BVH) optimized for streaming large-scale 3D city models in multiple resolutions. A new capability that enables the consumption of CityGML content, without data conversion, directly in web-enabled systems. To demonstrate this concept, we evaluated the suitability of encoding a CityGML 3.0 indoor model for one of the Stuttgart University of Applied Sciences (HFT Stuttgart) campus buildings, using I3S Building Scene Layer (BSL). I3S BSL is a new enhancement provided in the OGC I3S version 1.3 community standard enabling the representation of building elements, such as roofs, walls, floors, doors, windows, etc., in a hierarchical structure of layers and sub-layers, combined with BVH optimization. The results proved that the I3S BSL format successfully preserves the geometry, hierarchical organization, and semantic relationships among CityGML building classes, surpassing the capabilities of a generic CityGML conversion-based implementations and therefore making a promising foundation for an enhancement of the CityGML 3.0 building model using I3S encoding. This concept can be further extended in the future to other thematic modules of CityGML 3.0, for further development of I3S encoding of CityGML 3.0.