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Copyright © 2012 Op en G eos pati al Consortium
Figure 15 : Persp ective i mag ery fro m a WVS displayed in the 3D viewer XNavig ato r. The monta ge shows 3D con ten t from W3 DS left and WVS right for the sa me camera position.
8.10.2 Re sults
The setup was tested with both Web View Services provided by HPI. The first one was containing a subset of the Berlin model with 2 areas with textured buildings and a
complete textured terrain model. The second one was containing the complete 3D model of Paris as described in section 7.1.1. It was possible to switch between both at runtime
Figure 15. The resulting imagery was almost perfectly matching the underlying OSM- 3D model. Only minor perspective deviations could be observed.
8.10.3 Proble ms and solutions
The underlying 3D model used by the WVS may be defined in a local coordinate system, e.g. UTM. In this case it is impossible to perfectly merge the perspective imagery with a
3D globe model as used by the osm-3d.org project. However the effect is barely visible at the scales used in this experiment. It becomes only visible when zooming out and
requesting an overview image.
Also, the problem of different height references becomes visible again as a vertical shift of the displayed buildings and terrain when switching to the WVS-generated image in
XNavigator. This is because, on the one hand, the WVS provides images of the Berlin building models and a terrain model that is matching perfectly this building data and, on
the other hand, the 3D building models generated and provided by the OSM-3D W3DS are based on a different terrain model.
8.11 Sharing and displaying W VS image ry in we b browse rs
8.11.1 Sharing static 3D vie ws
Based on its HTTP-GET binding, the WVS allows for encoding requests for an image showing a specific 3D view on a 3D scene by URL. As these rendered 3D views are
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41 compressed and formatted by standard image formats e.g., JPEG, PNG they can be
easily integrated, e.g., in website or generally in web-based applications. Also these URL encoding 3D views can be easily shared with others, e.g., through sending by email or
posting to social media networks.
An example WVS GetView requesting for accessing a 3D view showing the Louvre in Paris is:
http:HPI.3DPIE.OGC.orgParisWVS?SERVICE=WVSVERSION=0.3.0REQUES T=GetViewCRS=EPSG:4326PORTRAYALS=WIDTH=640;HEIGHT=640;Projectio
ns=Perspective,2.336462,48.860645,70,2.336462,48.861145,35,0,0,1,90,90,1,90000;IM AGELAYERS=COLOR;FORMATS=imagejpeg;QUALITIES=95LAYERS=terrain,bl
dgsSTYLES=default,textured
8.11.2 JavaScript-base d inte ractive client
The HPI 3D Web Display Client is a 3D client application that is running in a web browser. It is mainly implemented in JavaScript and thus can be integrated, e.g., into web
portals and web applications.
The client is requesting 3D views as images from the underlying Web View Service. These images are displayed to a client user, i.e., no 3D rendering capability is required at
the client-side. Also the client provides a user interface that allows a user to interactively navigate through 3D portrayals in a manner that is similar to 2D map clients such as
Google Maps. For example, when a user moves the virtual camera foreword, a new image that represents this new 3D view is requested and displayed; through this a step -
by-step navigation in the virtual scene is possible.
Additionally, if available at the client-side, the HPI Web Display Client exploits the WebGL-capabilities of a web browser and requests not only a single image but a
complete panorama i.e., six sides of a cube map from the Web View Service, drapes these on a cube around the virtual camera, and allows the user to look around in the scene
in an highly interactive manner. As mainly based on JavaScript technology, the HPI Web Display Client can also be used in web browsers running on a mobile device.
The HPI Web Display Client has been used to access and explore the Paris 3D city model Figure 16.
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Figure 16 : HPI 3D W eb Display Cli ent running in a web browser allowing to ex plore the 3 D Pa ris data set.
8.12 Displaying W VS image ry on mobile clie nts
