Web3D City Model Contest Winners Announced

Contributed by: 
Volker Coors and Anita Havele

The 2015 Web3D City Model Contest award winners were announced in June at the 20th Annual Web3D Conference in Crete, Greece. http://web3d2015.web3d.org/

In late 2014, The Web3D Consortium and the Open Geospatial Consortium (OGC) announced to their members the Web3D City Model Contest competition for the best browser-based 3D rendering of a city. The contest was organized to encourage development of software solutions to stream to a client large 3D city models including textured buildings, terrain, and sensor data. The aim of the competition was to demonstrate the state of the art of browser-based 3D visualization of city models as well as to provide a starting point to compare different streaming solutions. The results provide valuable insights for the ongoing development of the OGC’s 3D Portrayal Service (3DPS) candidate standard and its interoperability with Web3D standards.

As a minimum requirement, the implementation had to operate as a Web Service. The client was required to be browser-based and to have the capability to select individual features (e.g. a building) and display further information about the selected feature. Further, the Web Service and the streaming protocol had to be documented and open. All competitors were provided the same source data:the open data CityGML model of Rotterdam, and terrain data. Any freely accessible data (water level, weather forecast, or other sensor/model data), maps and other features could be added at the implementer’s discretion. (See the submission instructions at http://web3d2015.web3d.org/competition.html).

This year’s winners received their awards at the 20th International ACM-SIGGRAPH Conference on 3D Web Technology in Heraklion, Crete, Greece. The winners received financial support to attend the conference. They were recognized for their creativity in addressing a 3D geospatial use case with solutions characterized by high performance in data loading, interactivity in the client, diversity of data rendered, and interoperability and openness. The winners were:

  • GeoPlex GmbH: Hannes Gräuler and Frederik Hilling -- attended and accepted their award in the Industry Solutions category.

  • Technical University of Munich: Kanishk  Chaturvedi  and Zhihang Yao -- accepted their award in the Student category.

The GeoPlex solution is implemented in pure WebGL (Java-Script), based on a heavily modified OpenWebGlobe (http://www.openwebglobe.org/) codebase. The server side consists of a GeoDjango application and a PostgreSQL database with PostGIS support. All tile types (image, terrain, geometry) use the same TMS-like slippy map convention. The tile types contain neither distinctive geometries nor feature attributes. In order to enable the client to query individual features, the solution follows the FeatureInfoByRay concept of OGC’s 3D Portrayal Service Standard. Two points are sent to the server: the current camera position and the direction of the mouse click. Thus it is possible to generate a ray and return the first building that is hit by that ray, highlighting the geometry and showing the attributes to the user. OpenStreetMap data (OSM) was integrated to generate 3D symbols for bus stops and parking spots.

The solution can be explored at http://rotterdam.b.geoplex.de/.

The TU Munich solution utilizes the Cesium JavaScript framework on top of HTML5 which allows for performing Ajax requests to access remote data hosted in a cross domain. The 3DCityDB was used to generate tiles stored in KML/COLLADA files from the CityGML data. Furthermore, the tiling manager in the web client was developed to support the tiling of large 3D city models and dynamic loading of the tiles. Utilizing multi-threading capabilities of HTML5, the time-costly operations such as parsing of multiple 3D objects are delegated to background threads running in parallel. At the same time, another thread monitors the interactions with the virtual camera and takes care of loading and unloading the data tiles according to their visibility. In addition, the user can control the dynamic elements of 3D building models using JavaScript commands embedded within Cesium JavaScript API. Cesium was extended to support KML network links, caching, dynamic loading and unloading of tiles, and 3D object highlighting.

The solution is accessible at: http://www.3dcitydb.net/3dcitydb/fileadmin/3DWebClient/index.html .

The student award was co-sponsored by the 3D city model Working Group of the German Cartographic Society (DGfK) and the German Society for Photogrammetry, Remote Sensing and Geoinformation (DGPF).

Hannes Gräuler and Frederik Hilling of GeoPlex receive their award from the Web3D Consortium. From left to right:  Nicolas Polys of the Web3D Consortium, Hannes Gräuler, Frederik Hilling and Mike McCann of the Web3D Consortium. Missing: Volker Coors, HFT Stuttgart / OGC who was in hurry to catch his flight back home.

The OGC and the Web3D Consortium have both been working to address the need for interoperability as well as the content challenges of volume, access speed, and diversity of devices. The Web3D Consortium has focused on open standards for real-time 3D visualization, including streaming. Their members developed a Geospatial Component extension for X3D. The OGC has focused on developing a service interface to provide interoperable access to 3D geospatial data servers. In 2013, the OGC, building on work done in both organizations, initiated a standards working group to develop a 3D Portrayal Service Standard.

Volker Coors is a Professor at Hochschule für Technik Stuttgart and Anita Havele is Executive Director at Web3D Consortium.