1. IEEE VR 2003 Ribbon Networks for Modeling Navigable Paths of Autonomous Agents in Virtual Urban Environments Peter Willemsen Joseph Kearney Hongling Wang School of Computing Dept. Of Computer Science University of Utah University of Iowa

2. IEEE VR 2003 Research Overview  Dynamic VE –Vehicles, pedestrians, etc… –Lots of them!  Behavior and scenario programming  Environment Modeling Adapted to the needs of behavior and scenario programs Environment ScenarioBehavior

3. IEEE VR 2003 Motivation  Virtual environments as laboratories for psychological study –Child bicycle-riding behavior  Dynamic virtual environments need activity –Realistic behaviors –Replicable scenarios  Spatial awareness –What routes are accessible? –Where are other objects? –What constraints are important?

4. IEEE VR 2003 Focus of Talk - Environment  Geometric Information –Shape and curve of pathways  Topological Information –Interconnections between pathways  Logical information –Rules governing behavior  Occupancy Information –Locations of objects

5. IEEE VR 2003 Related Research  Farenc et al - Informed Environments –Eurographics 1999 –Behavioral content connected to scene graph  Donikian and Thomas - VUEMS –Eurographics 2000, CGI 1997 –Comprehensive system for modeling urban networks of streets, sidewalks, and tramways  Road modeling for driving simulation –Civil engineering design of roadways –Desirable properties for high speed roadways

6. IEEE VR 2003 Ribbon Networks  Model urban streets, sidewalks, and navigable ways as ribbons in space –Curvilinear coordinate system –Arc-length parameterized spline –Fast lookup based on distance  Defines geometry and orientation of navigable surface  Provides frame of reference for local spatial relationships  Annotations (e.g. speed zones, passing regions, features)

7. IEEE VR 2003 Ribbon Network Computations  Map (X,Y,Z) (D,O,L)  Closest Point Computation –Typical bottleneck –Usual optimization techniques fail Slow convergence and divergence  Hybrid Method –Combines Newton’s method and quadratic minimization ‒ fast and robust (D, O, L)

8. IEEE VR 2003 Ribbon Network Attributes  Ribbons capable of representing (all?) types of roadways –Curvy, straight, engineering specified  Cracks due to modeling errors fixed by imperceptible numerical nudges  Attributes annotate ribbon structure –Lanes (parallel streams channel traffic flow) –Speed limit signs, passing zones, and behavior associated objects, such as flag men  Ribbon establishes convenient local access to attributes

9. IEEE VR 2003 Intersections  Splice together incoming and outgoing lanes –Corridors (single lane ribbons)  Dependencies –Corridor relationships –Crossing, merging, crosswalk, right of way, traffic control  Zero-length intersections Change road cross-section  Hierarchical intersections –Pedestrians intersections  Type and instance Corridor C 0 (crosses C 1 ) (merges_with C 2 ) (right_of_way C 1,C 2 )

10. IEEE VR 2003 Paths as Overlay Ribbons  Single-lane ribbon overlayed on the road network  Simplify behavior at road/intersection junctures –Tracking –Collision avoidance  Dynamically composed by individual behaviors  Provide egocentric, local coordinate system for environment queries Insert picture of Washington and Clinton intersection overlaid with a path ribbon.

11. IEEE VR 2003 Occupancy  Spatial relationships based on ribbon structure (INSERT PICTURE HERE)  Occupancy queries: Two Forms –Leader First object on ribbon segment –List of leaders Ordered list of objects on ribbon segment

12. IEEE VR 2003 Results  Ribbon network forms substrate for the Hank Simulator General purpose virtual environment software  Simulator used hundreds of hours in “production” mode Database queries (almost) never fail  Behavior code is greatly simplified  Environment Description Format (EDF) Modeling language for road networks

13. IEEE VR 2003 The System in Action (movie)

14. IEEE VR 2003 Conclusions  Solid conceptual model of urban landscape  Ribbon networks –Geometry matches shape and curve of pathways –Topology describes interconnections –Logical attributes provide constraints and socio-cultural aspects –Occupancy sets up inter-object relationships  Behaviors obtain spatial awareness  Environment model is efficient, robust, and simple –Supports behavior and scenario control programs

15. IEEE VR 2003 Future Work  Automatic generation of models from GIS Data  Terrain from roads  Incorporating pedestrian models  Integration into physical environment system –VTerrain.org

16. IEEE VR 2003 Collaborators University of Iowa, Computer Science Jim Cremer Zhihong Wang Scott Davis Jill Secher University of Iowa, Psychology Jodie Plumert University of Iowa, Math Ken Atkinson

17. IEEE VR 2003 Acknowledgments  Visual Database Expertise –Joan Severson –Shayne Gelo –Kate Kearney  NSF Support: CDA-96-23614, INT- 9724746, EIA-0130864, and IIS-0002535

18. IEEE VR 2003

20. Importance of Environment  This slide was earlier, but didn’t like it there…  Not sure if I like it in any case…  Behaviors are difficult to create! –Time consuming  Part of Environment!  Behaviors and enviroment mesh together  Provide sets of queries for behavior –Where am I? (Spatial awareness) –Who’s near me? (Occupancy) –Where can I go from here? (Geometry, topology) –What rules should I obey here? (Logic)

21. IEEE VR 2003 Modeling Language  System is built upon a language  Describes the ribbon networks  Example

22. IEEE VR 2003 Query Environment Database  System provides run-time queries –Where am I? –Where can I go? –Other examples Overview the general query structure of the run- time system Abstract behavioral queries