Using glTF for streaming CityGML 3D city models

In this paper, we describe an approach for efficiently streaming large and highly detailed 3D city models, which is based on open standards and open source developments. This approach meets both the rendering performance requirements in WebGL enabled web browsers and the requirements by 3D Geographic Information Systems regarding data structuring, geo-referencing and accessibility of feature properties. 3D city models are assumed to be available as CityGML data sets due to its widespread adoption by public authorities. The Cesium.js open source virtual globe is used as a platform for embedding custom 3D assets. glTF and related formats are used for efficiently encoding 3D data and for enabling streaming of large 3D models. In order to fully exploit the capabilities of web browsers and standard internet protocols, a series of filtering and data processing steps must be performed, which are described in this paper.