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Given by Remek Trzaska, Pawel Roman, Chris Walczak at Rome Lab Quarterly Review for CIV on October 1 96. Foils prepared 22 February 97
Outside Index
Summary of Material
| Application Model |
| System Overview |
| Wavelets |
| Mesh simplification |
| Triangulation |
| Open Inventor (fast VRML!) |
| Overall Communication Architecture |
| Communication with the Collaboratory System |
| GIS Protocol |
| Future enhancements |
Denote Foils where Image Critical
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3D Geographic Information System
Application Model
System Overview
Wavelets
Wavelets (cont'd)
Mesh simplification
Triangulation
Open Inventor
Overall Communication Architecture
Overall Communication Architecture (cont'd)
Communication with the Collaboratory System
GIS Protocol
Future enhancements
Outside Index
Summary of Material
HTML version of Basic Foils prepared 22 February 97 
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| Remek Trzaska, Pawel Roman, Chris Walczak |
HTML version of Basic Foils prepared 22 February 97 
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Master/Slave model:
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| HTTP |
| server |
| Master |
| Application |
| Slave |
| App. #1 |
| Slave |
| App. #2 |
| CIV |
| Control Application |
| Control connection |
| Binary data connection |
HTML version of Basic Foils prepared 22 February 97
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| Goal: visualization of terrain with multiple kinds of data, including satellite images, maps and weather info |
| Open Inventor used as a graphic library and a windowing toolkit |
| "Earth surface" is build with triangles |
| Imaginary data (maps, satellite images, etc.) is projected on the surface |
| DEM & imaginary data is compressed using wavelets |
| Adaptive mesh simplification |
| Delaunay triangulation |
HTML version of Basic Foils prepared 22 February 97
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| Wavelet decomposition extracts the most important information (low frequencies) and less meaningful details (higher frequencies) |
to compress the wavelet coefficients we use Embedded Zerotree Algorithm:
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HTML version of Basic Foils prepared 22 February 97
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| Embedded stream lets any application use only a fraction of a stream to obtain some approximation of a image: |
| Whole stream (14times) 62% of the stream (22t.) 14% (100t.) |
| Compression ratios used in the system: ~48 times for DEM, ~25 for textures |
HTML version of Basic Foils prepared 22 February 97
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| A full mesh of triangles build on n2 points (nodes) consists of 2(n-1)2 triangles |
| Most of nodes can be removed without a visual loss of quality |
| Which of the above terrains was built with only 10% of nodes??? (Answer: the right one) |
HTML version of Basic Foils prepared 22 February 97
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| After mesh simplification, the remaining nodes have to be connected into a set of triangles |
| We use a fast divide-and-conquer 2D Delaunay triangulator. |
| Every triangle's circumcircle contains only the vertices of this triangle |
HTML version of Basic Foils prepared 22 February 97
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| OI is a set of C++ classes designed for developing high-performance graphics applications |
Its extensibility allows to overcome some of its drawbacks:
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HTML version of Basic Foils prepared 22 February 97
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HTML version of Basic Foils prepared 22 February 97
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Two levels of communication
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| GIS Control Panel is connected with a collaboratory daemon by means of a socket |
Two message channels
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HTML version of Basic Foils prepared 22 February 97
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| Messages sent from the master to all the |
| slaves via the control application: |
| Camera Position Change–the master has made a movement in his GIS window |
| New URL–the new virtual world has been chosen to be displayed |
| Windows Contents–the master has turned on/off one of the windows or changed its content (map/weather, walk/fly view) |
HTML version of Basic Foils prepared 22 February 97
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| Usage of the SoLevelOfDetail class to improve displaying speed |
| Dynamic downloading of the necessary data while the system is being viewed |
| Animation of objects according to control information received from the simulation engine |