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LSVE: Tips and Tricks

LSVE: Tips and Tricks. Manuel Oliveira Computer Science Department University College London. Contents. Issues of Scale Area Of Interest Management (AOIM) Packet Manipulation Level Of Detail Temporal Distortion Interaction Techniques Hacks: Time Bucket Processing Discussion.

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LSVE: Tips and Tricks

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  1. LSVE: Tips and Tricks Manuel Oliveira Computer Science Department University College London

  2. Contents • Issues of Scale • Area Of Interest Management (AOIM) • Packet Manipulation • Level Of Detail • Temporal Distortion • Interaction Techniques • Hacks: Time Bucket Processing • Discussion

  3. Issues of Scale

  4. AOIM: Overview Entity 1 Flow 1 Group 1 Host 1 Entity 2 Flow 2 Entity 3 Flow n Group n Host n Entity n Application Network Naming Mapping Forwarding

  5. Just give each client enough to fool the user • Interest: visibility, awareness, functional, … • Network and computational constraints AOIM: Goals • A user is NOT an omniscient being • A user is NOT interested in every event • A client is NOT able to process everything

  6. AOIM: Types • Static Grid • Hierarchical Grid • Locales • Aura • Region • Filtering • Nearest Neighbours

  7. AOIM: Static Grid • 1 Cell = 1 Group • Hexagon regular shape • Tied into the grid – static • Send current cell • Receive neighbours • Any architecture (distributed) • NPSNET (DIS)

  8. AOIM: Hierarchal Grid • 1 Cell = 1 Group • Square cells • Send current cell • Receive current cell • Any architecture (distributed) • Exceeds threshold, expand Threshold = 5

  9. AOIM: Locales • 1 locale = 1 group • Locale is arbitrary shape • Locale placement is static • Associated transform matrix • Any architecture (distributed) • MERL

  10. AOIM: Locales • 1 locale = 1 group • Locale is arbitrary shape • Locale placement is static • Associated transform matrix • Any architecture (distributed) • MERL

  11. AOIM: Locales • 1 locale = 1 group • Locale is arbitrary shape • Locale placement is static • Associated transform matrix • Any architecture (distributed) • MERL

  12. AOIM: Aura Aura • Nimbus, Aura, Focus • Auras intersect = group • Focus, Nimbus = awareness • Aura Manager • Client/Server • MASSIVE Focus Nimbus

  13. A - Update CreateUpdateRegion AOIM: Region (High Level Architecture) Federate A Routing Space

  14. B - Update Federate B CreateObject AOIM: Region (High Level Architecture) Federate A Routing Space A - Update

  15. C - Subscribe Federate C SubscribeRegion AOIM: Region (High Level Architecture) Federate A Federate B Routing Space A - Update B - Update

  16. B A C AOIM: Filtering • Line of sight • Entity visible = group • Client/Server • RING

  17. AOIM: Nearest Neighbours • 1 group = quorum • Computational/Network constraints • Client/Server • Community Place

  18. AOIM: Nearest Neighbours • 1 group = quorum • Computational/Network constraints • Client/Server • Community Place

  19. Packet Manipulation: Compression • Bandwidth requirements is determined by amount of data sent/received per second • Approaches to reduce data: • Compress the data payload of each packet – RLE • Compress the data flow – MPEG style • Compression gateways between bandwidth bottlenecks

  20. Packet Manipulation: Aggregation • Approaches: • Wait for n packets before sending a single packet with them • Use a timer, when expires send packets available • Hybrid • Models: • Host based • Server based: Aggregation done on broader scale = faster

  21. Packet Manipulation: Aggregation • Problems: • Increased latency • Retransmission becomes a problem • Outdated information • Inefficient

  22. Distance function Layered nimbus Level Of Detail • Integrate distance • 1 group = 1 send rate • Layered multicast

  23. Interaction Techniques: Ghosts Host A Host B Request Lock Wait Lock Lock Resolved

  24. Temporal Distortion: Ping Pong

  25. Temporal Distortion: Ping Pong

  26. Temporal Distortion: Ping Pong Render Ball at remote time (delay) Render Ball at current time

  27. Hacks: Time Bucket Processing Client B Client A

  28. Hacks: Time Bucket Processing Client B Client A

  29. Hacks: Time Bucket Processing Client B Client A There is X ms discrepancy between clients Impossible to eliminate latency

  30. Artificial Latency Current Bucket Hacks: Time Bucket Processing Local Player Time Bucket Time Period Bucket Processing <= Bucket Time Period Introduce Artificial Latency (AL): 4 time periods

  31. Event T0 AL Hacks: Time Bucket Processing Local Player Time Remote Player

  32. Transmission Delay Synchronization Delay Hacks: Time Bucket Processing Local Player Time Event T0 Remote Player

  33. Discussion

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