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10.5 Potential change s in W 3DS and W VS inte rface de finitions
10.5.1 W 3DS GetTile ope ration
Fraunhofer IGD suggests making the W3DS GetTile less client-dependent, i.e., to release a W3DS client from computing tile boundaries Section 10.3.2.
10.5.2 W 3DS custom exte nsions
Fraunhofer IGD proposes to specify a reserved vendor prefix for custom extensions. This could take the form of specifying that parameters beginning with “x-“ or “x-
vendor- ” are never specified as a part of the standard e.g. the IETF uses such
prefixes. Although this should be WSC business, we didn’t identify a comparable mechanism there.
10.5.3 Re thinking the conce pt of data laye rs
As in the WMS, the LAYER parameter of the W3DS GetScene request and the WVS GetView request specifies which data sets a server shall consider for processing the
operation responses. However, while the concept of layers and drawing them one upon the other fits well for the WMS, this does not really fit for the 3D case. In the case of
W3DS and WVS we are even more dealing with graphics representation of feature sets. This could be reflected better, by renaming the LAYER parameter, and making this
conceptual difference clear in the service specifications.
10.5.4 Styling data laye rs
Closely linked to the meaning of “layers” or rather feature representations is the issue of styling selected 3D data sets. For example, thematic maps i.e., raster data to use, e.g., as
textures could be modeled in two different ways: First, a server could advertise thematic maps as
separate “data layers”. Second, a server could provide such textures as a specific style,
e.g., of a terrain “layer”. While the first way is closer to drawing “layers” on top of each other, the latter is closer to the idea of selecting feature data to portray and also
closer to how, e.g., CityGML is modeling the appearance of feature data.
10.5.5 Se mantics of data laye rs
To allow W3DS or WVS clients to request a meaningful representation 3D graphics data or image of the 3D environment provided by the servers, it would be required to provide
some kind of semantics along with the metadata describing the data sets offered by the WVS servers. So a W3DS or WVS client could, e.g., ensure to always include a terrain
model in the list of requested data set. Allowing a client to distinguish and request offered data sets according to their semantics and to their importance for a scene representation
could help a client user to assemble a specific scene representation and so could help to reduce the size of transferred data.
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11 Future Work Next steps
Only selected issues of service-based, standards-based 3D portrayal have been tackled by 3DPIE. Some issues that could be relevant to look at, e.g., in future phases of 3DPIE, are
described in the following.
11.1 Navigation in the 3D sce ne
