MMO Features
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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)
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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.
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Interest areas: Events of items within an interest area are automatically received.
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Interest areas have two interest thresholds. Items that enter the inner radius become visible;
items that leave the outer become invisible. This optimization reduces frequent visibility changes.
Inner and outer radius - 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
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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.
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Interest areas have two interest thresholds. Items that enter the inner radius become visible;
items that leave the outer become invisible. This optimization reduces frequent visibility changes.
- Manual interest management: Clients can manually (un-)declare interest in items.
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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.