Characterizing Virtual
Population in Games


                         1
World of Warcraft




                    2
Use an add-on written in Lua




                               3
monitor
1100 random players
   over 71 days




                      4
median num of players per poll
  vs time of the day polled
                                 5
CDF of all session length, and
median session length of each player
                                       6
sufficiently long session length
     good for P2P games




                                  7
8
can use level to
predict session length?




                          9
CDF of median downtimes and
median session length of each player
                                       10
Availability of players (time online/total time)
                in February 2007
                                        ...
12
13
monitor
3 locations
Stormwind City
Stanglehorn Vale
Burning Steppes




                   14
15
can use zone to
predict session length?




                          16
density: num of players* in a
           zone
    *: out of 1100 players tracked




                                     ...
Mean Location density of 117 locations

                                         18
Difference in Density between Dec and Feb

                                            19
20
dynamic load balancing not
         needed?




                             21
“My life is so great that I literally wanted a second one!”
- Dwight Schrute,The Office


                                 ...
256x256 m regions.

                     23
24
25
26
27
avatar mobility:
who is where, when


                     28
why do we care?



                  29
research in systems
 support for NVE


                      30
31
How to partition a world into regions
and assign regions to servers considering

- communication cost
- hand-over rate
- b...
33
How to predict avatar movement (end
therefore what a user will see next)?




                                        34
35
AoI-based scheme




                   36
How many connections?

How stable are the connections?




                                  37
supernode-based scheme




                         38
How to pick supernodes?

How stable are the supernodes?




                                 39
how to simulate
 avatar mobility?


                    40
random walk
  random waypoint
clustered movement
          :

                     41
or,
  small-scale
implementation


                 42
no large-scale NVE
available until recently


                           43
482,594
residents logged in between 2-9 June 2008




                                            44
secondlife.com/whatis/economy-graphs.php
                                           45
• collect mobility traces of
 avatars in Second Life

• what it means w.r.t. systems
 design for NVEs?


                 ...
collecting traces



                    47
how do avatars move
 inside a distributed
virtual environment?


                        48
how are avatars
distributed within a
       region?


                       49
how long do they stay
   at a location?


                        50
do they move in
    groups?


                  51
etc.



       52
FPS   MMORPG   NVE




                     53
Linden, can we get access to
the server traces?


                   No.

                               54
• Wrote our own client
• Parses packets using libsecondlife
• Insert bots into regions
• Log positions of avatars every 10...
difficulties



              56
running out of memory



                        57
anti-bots policy



                   58
over crowded region



                      59
inter-region tracking



                        60
• Wrote our own client
• Parses packets using libsecondlife
• Insert bots into regions
• Log positions of avatars every 10...
who is
   where,
   when
(doing what)

               62
63
Freebies

           64
The Pharm

            65
Isis

       66
Ross

       67
Mobility Patterns



                    68
Freebies: number of visits to a cell

                                       69
Freebies: average pause time in a cell

                                         70
Freebies: average speed in a cell

                                    71
Isis: number of visits to a cell

                                   72
caching/prefetching
based on popularity of
      locations?


                         73
Isis: average pause time in a cell

                                     74
pick supernodes from
   sticky location?


                       75
Isis: average speed in a cell

                                76
mobility model:
random walk +
   pathway ?


                  77
churn rate



             78
79
80
Reasonably high churn (up to 6/min)

                                      81
1 min    10 min



                     1 hr   2 hr




Highly skewed. Some stay for hours.

                             ...
cannot pick
supernodes uniformly


                       83
clustering of
   avatars


                84
meeting: encounter
 between two avatars
(within each other AoI)


                          85
Meet many different avatars.

                               86
1 min
                       1 hr



              10 min          2 hr




   Most meetings are short.

                 ...
Meeting size is large.

                         88
high overhead in
maintaining AoI
   neighbors


                   89
meeting stability:

  avg meeting size
       over
 num of avatars met
                      90
Wide range of stability

                          91
other tidbits



                92
little temporal variations

can use historical information
      to predict future


                                 93
rotate 18% of the time

Second Life’s prefetching is
        wasteful


                               94
25-35% revisits the same
     region in a day

   region-based caching?


                           95
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CS4344 Lecture 10: Player Dynamics

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CS4344 Lecture 10: Player Dynamics

  1. 1. Characterizing Virtual Population in Games 1
  2. 2. World of Warcraft 2
  3. 3. Use an add-on written in Lua 3
  4. 4. monitor 1100 random players over 71 days 4
  5. 5. median num of players per poll vs time of the day polled 5
  6. 6. CDF of all session length, and median session length of each player 6
  7. 7. sufficiently long session length good for P2P games 7
  8. 8. 8
  9. 9. can use level to predict session length? 9
  10. 10. CDF of median downtimes and median session length of each player 10
  11. 11. Availability of players (time online/total time) in February 2007 11
  12. 12. 12
  13. 13. 13
  14. 14. monitor 3 locations Stormwind City Stanglehorn Vale Burning Steppes 14
  15. 15. 15
  16. 16. can use zone to predict session length? 16
  17. 17. density: num of players* in a zone *: out of 1100 players tracked 17
  18. 18. Mean Location density of 117 locations 18
  19. 19. Difference in Density between Dec and Feb 19
  20. 20. 20
  21. 21. dynamic load balancing not needed? 21
  22. 22. “My life is so great that I literally wanted a second one!” - Dwight Schrute,The Office 22
  23. 23. 256x256 m regions. 23
  24. 24. 24
  25. 25. 25
  26. 26. 26
  27. 27. 27
  28. 28. avatar mobility: who is where, when 28
  29. 29. why do we care? 29
  30. 30. research in systems support for NVE 30
  31. 31. 31
  32. 32. How to partition a world into regions and assign regions to servers considering - communication cost - hand-over rate - balancing server load : 32
  33. 33. 33
  34. 34. How to predict avatar movement (end therefore what a user will see next)? 34
  35. 35. 35
  36. 36. AoI-based scheme 36
  37. 37. How many connections? How stable are the connections? 37
  38. 38. supernode-based scheme 38
  39. 39. How to pick supernodes? How stable are the supernodes? 39
  40. 40. how to simulate avatar mobility? 40
  41. 41. random walk random waypoint clustered movement : 41
  42. 42. or, small-scale implementation 42
  43. 43. no large-scale NVE available until recently 43
  44. 44. 482,594 residents logged in between 2-9 June 2008 44
  45. 45. secondlife.com/whatis/economy-graphs.php 45
  46. 46. • collect mobility traces of avatars in Second Life • what it means w.r.t. systems design for NVEs? 46
  47. 47. collecting traces 47
  48. 48. how do avatars move inside a distributed virtual environment? 48
  49. 49. how are avatars distributed within a region? 49
  50. 50. how long do they stay at a location? 50
  51. 51. do they move in groups? 51
  52. 52. etc. 52
  53. 53. FPS MMORPG NVE 53
  54. 54. Linden, can we get access to the server traces? No. 54
  55. 55. • Wrote our own client • Parses packets using libsecondlife • Insert bots into regions • Log positions of avatars every 10s 55
  56. 56. difficulties 56
  57. 57. running out of memory 57
  58. 58. anti-bots policy 58
  59. 59. over crowded region 59
  60. 60. inter-region tracking 60
  61. 61. • Wrote our own client • Parses packets using libsecondlife • Insert bots into regions • Log positions of avatars every 10s 61
  62. 62. who is where, when (doing what) 62
  63. 63. 63
  64. 64. Freebies 64
  65. 65. The Pharm 65
  66. 66. Isis 66
  67. 67. Ross 67
  68. 68. Mobility Patterns 68
  69. 69. Freebies: number of visits to a cell 69
  70. 70. Freebies: average pause time in a cell 70
  71. 71. Freebies: average speed in a cell 71
  72. 72. Isis: number of visits to a cell 72
  73. 73. caching/prefetching based on popularity of locations? 73
  74. 74. Isis: average pause time in a cell 74
  75. 75. pick supernodes from sticky location? 75
  76. 76. Isis: average speed in a cell 76
  77. 77. mobility model: random walk + pathway ? 77
  78. 78. churn rate 78
  79. 79. 79
  80. 80. 80
  81. 81. Reasonably high churn (up to 6/min) 81
  82. 82. 1 min 10 min 1 hr 2 hr Highly skewed. Some stay for hours. 82
  83. 83. cannot pick supernodes uniformly 83
  84. 84. clustering of avatars 84
  85. 85. meeting: encounter between two avatars (within each other AoI) 85
  86. 86. Meet many different avatars. 86
  87. 87. 1 min 1 hr 10 min 2 hr Most meetings are short. 87
  88. 88. Meeting size is large. 88
  89. 89. high overhead in maintaining AoI neighbors 89
  90. 90. meeting stability: avg meeting size over num of avatars met 90
  91. 91. Wide range of stability 91
  92. 92. other tidbits 92
  93. 93. little temporal variations can use historical information to predict future 93
  94. 94. rotate 18% of the time Second Life’s prefetching is wasteful 94
  95. 95. 25-35% revisits the same region in a day region-based caching? 95

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