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Copyright © 2012 Op en G eos pati al Consortium
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
The motivation of this experiment was to exploit a WVS server from a 3D client application running on a mobile device for interactive 3D portrayal.
For this experiment, we used the HPI 3D Mobile Client, which provides an interactive user experience based on image-based rendering technologies. Currently it is primarily
provided as an App for iOS devices, e.g., iPhone and iPad; however, as implemented in a platform-independent way, it could be ported to other mobile platforms, too. The Mobile
Client provides continuous 3D visualization and creates an interactive user experience that is comparable to common desktop 3D clients. This is reached through image-based
rendering techniques: The client consumes not only color images from a Web View Service but also depth representations and object id images , from which a 3D scene is
reconstructed and rendered in real-time at the client side. All interaction techniques are made through the iPads or iPhones multi-touch display.
8.12.1 W orkflow
The client is implemented as an iOS application. Right after starting the App, the client is requesting a specific App server to gather information about the App configuration and
the WVS instance to connect to. For a specific camera position, the client then requests images for the six faces of a cube that is surrounding the virtual camera. For each of these
faces it requests color images, depth representations, and object id images. To reduce network load and allow for server-side optimizations, all faces and layers are requested
by a single WVS request. An example for retrieving multiple WVS image layers of such cube face by one GetView request is:
Copyright © 2012 Op en Geos pati al Consortium
43 http:HPI.3DPIE.OGC.orgBerlinWVS?SERVICE=WVSVERSION=0.3.0REQUES
T=GetViewCRS=WGS84BACKGROUND=defaultPORTRAYALS=WIDTH=256; HEIGHT=256;Projections=Perspective,13.409292,52.518795,210,13.408311,52.521346,
120,0,0,1,90,90,1,10000000;IMAGELAYERS=COLOR,DEPTH,OBJECTID;FORMAT S=imagejpeg,imagepng,imagepng;QUALITIES=80,100,100LAYERS=terrain,BERL
INSTYLES=orthophoto,default
According to such request the server loads the required data, renders the requested image layers, encodes those, e.g., in standard image formats, and returns those as HTTP multi-
part response.
The client is consuming this data from the received data stream and is using it in various ways for visualization purposes . Firstly, it is rendering the cube surrounding the virtual
camera and drapes the retrieved images on this cube. This gives the users the illusion of being positioned in a complete 3D environment. The user can explore this environment,
e.g., by rotating the virtual camera or zooming in and out. In the case of zooming in, e.g., the client requests new color images showing the actual scene section in more detail.
Secondly, the client is reconstructing and rendering a textured 3D mesh from the depth layer provided by the WVS, i.e., it is no more displaying the textured cube. In this mode
the client allows a user to move the virtual camera freely, e.g., moving it forwardbackwards or sideward.
Based on the object id layer requested from the server, the client is also capable to distinguish different objects and allow a user, e.g., to select and highlight specific objects
e.g., buildings and to rotate around such objects to inspect it.
Figure 17 : iOS App running on the iPad and iPhone providing WVS -bas ed access to and intera ctiv e visuali zation of the 3D Pa ris city mod el.
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8.12.2 Re sults
