1. C ROWD P ATCHES : P OPULATING L ARGE - S CALE V IRTUAL E NVIRONMENTS FOR R EAL -T IME A PPLICATIONS Barbara Yersin, Jonathan Maïm, Julien Pettré, Daniel Thalmann (2009)

2. O UTLINE Introduction Related Work Crowd Patches Results Conclusions and Assesments

3. I NTRODUCTION Crowd Patches approach Large-scale virtual environments Ability to generate in real-time Handle high density Low cost navigation simulation High motion quality

4. I NTRODUCTION Create small areas – patches Motion trajectories Static and dynamic objects Assemble patches to generate the environment Templates to design the crowd patches

5. R ELATED W ORK Global level Cell decompositions, voronoi diagrams Interactively handle large crowds Local level Ruled based, social forces, potential fields Lee et al. 2006 – Motion Patches

6. P ATCHES Endogenous objects (left) Periodic animation inside a patch Exogenous objects (right) Periodic motions, from one patch to another

7. P ATTERNS Faces with input/output information

8. P ATCH C REATION Assembly the patterns One for each face Get the information on static and endogenous objects Linearly initialize trajectories Make adaptations based on velocity Collision avoidance and smoothing Particle based Attraction points and repulsions

9. P ATCH CREATION

10. E NVIRONMENT CREATION Bottom-Up Approach Iteratively create and add patches (top) Top-Down Approach Decompose the geometric model of the environment into cells (bottom)

11. P ATCH TEMPLATES To aid the designer Generate patches from given templates Templates formed by: Static objects Endogenous objects Pattern types

12. P ATTERN T YPES Empty patterns No I/O – Represent borders with static obstacles One-way patterns Inputs or outpus – One way flows Specific I/O space distribution Limit the space of I/O – Narrow passages,lanes Specific I/O time distribution Limit the time of I/O – Crossings sidewalks at certain time

13. R ESULTS Bottom-up approach (without rendering) Top-down approach 20 fps Video!

14. C ONCLUSIONS Handle densely crowded large scale virtual environments Realistic motion Patches have identical time period Static patches Lacks variety Lacks interactivity

15. A SSESMENTS Well constructed and written Clearly explains: Objectives Motivation Contribution Discusses: Shortcomings of the method Alternatives Future work

16. A SSESMENTS Missing implementation details Experiments? Only 2 applications are considered Results Only result data is in terms of FPS

17. A SSESMENTS Performance Reasonable top-down approach results Bottom-up would be slow Real-time applications - limited Lack of dynamic updates Lack of goal queries

18. A SSESMENTS Visually convincing (+) Motions and animations Large scale virtual environments (+) On-line generation of the environment Densely crowded (-) Many characters but not really dense Narrow passages, doorways?

19. A SSESMENTS High quality/realistic motion (-) Avoidance is relatively poor Another fast approach might be integrated Prediction based? Collisions and pedestrian representations What if the trajectories in one patch are close enough? Clearance, personal space Maybe simple disk representations

20. Q UESTIONS & R EMARKS VR-Lab http://vrlab.epfl.ch/