MMO Features

• Region-based interest management

  • Square tile algorithm with variable width, height and tile size is implemented
  • Easily replaceable with other region algorithms (hexagonal, etc. see http://gram.cs.mcgill.ca/papers/boulanger-06-comparing.pdf)

• Items (Avatars, NPCs, shared game objects)

  • Clients can spawn, destroy and move items.
  • Items can have properties that are readable by other clients and
    changeable by the owner.
  • Item properties have a revision number: Clients that lose sight
    of an item for some time can compare the revision to determine
    if they need to receive updated properties.

• Interest automatically received.

  • Interest areas have two interest thresholds. Regions that enter
    the inner radius become visible; regions that leave the outer
    become invisible. This optimization reduces frequent visibility
    changes.

• Invisible item, out of range

  • Invisible item enters outer interest area
  • Invisible item enters inner interest area and becomes
    visible
  • Visible item leaves inner interest area
  • Visible item leaves outer interest area and becomes
    invisible

• Interest areas can be resized: Adjusting the view distance in
  proportion to the amount of seen items can be beneficial

  • To improve the performance in crowded areas or
  • To show distant items in areas with low population.

• Interest areas can be attached to any item: Whenever the item
  moves the interest area follows and changes the interest
  accordingly. This is especially useful to move the interest area
  with the own avatar.

• Detached interest areas can be moved freely. This is beneficial
  for camera flights.

• Clients can have multiple interest areas to show different parts
  of the world at the same time.

• Manual interest management: Clients can manually (un-)declare
  interest in items.

• Custom events can be sent through items to two possible targets:

  • The item owner
  • All clients that are interested in the item (item subscriber)

• Optimized position updates: Clients send updates only when they
  move.

• Duplicate user recognition: A subsequent user connection resets the
  previous connection.