Construction of Responsive Web Service for Smooth Rendering of Large SSC Dataset

Construction of Responsive Web Service for Smooth Rendering of Large SSC Dataset

P5 Presentation by Yueqian Xu


Main mentor: Martijn Meijers
Second mentor: Peter van Oosterom
Co-reader: Timothy Kol (Computer Graphics)


This research focuses on a smooth generalization of continuous 2D map based on a smooth 3D vario-scale geographical data structure. A Space Scale Cube (SSC) offers non-redundant geometric data for the different level of details. SSC model represents geographic data as a closed polyhedron, to generate a 2D map; SSC is intersected with the projection plane; resulting in a set of 2D polygons. However, problems emerge when creating maps with a large sized SSC dataset under web environment due to limited bandwidth and decoding speed. Repetitively transmitting data from the server to the client can be time and bandwidth consuming. A preprocess should be applied to a source that allows the follow-up development of an online traffic and time-saving prototype.

After preprocessing, large sized data will be subdivided based on octree algorithm to minimize transmission time from server to the client; moreover, accessible to WebGL. A prototype has been developed which enables smooth and simultaneous vario-scale map rendering against heavy user actions such as massive zooming and panning in a short period. Modified prototype schema allows query of only relevant data chunks by current viewport position; it prevents repeated loading of same chunks; what is more, repeated transmission of data from outside to GPU is eliminated. A tree structure is embedded at the client side that facilitates retrieve time. Rendering happens every frame; hence the prototype responses to heavy user actions simultaneously. Also, it can obtain coordinates in RD coordinate system by double clicking. After testing modified schema with a 9×9 dataset, fine performance of the prototype is indicated by a high average fps (57 fps) and low main memory occupation.

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