[Drajor]

I got inspired and started work on this. My theory is as follows, note that I do not know anything about the mob update packets yet so I have made some assumptions.

This approach aims to address two things;
- Improve NPC proximity aggro check performance.
- Add the concept of Mob 'visibility'.

Each (zone)instance has a quadtree which all Mob's are added to when they are created and removed from when they are destroyed. The quadtree provides a query(region) interface which returns a list of Mob* which are within this region.

-- Aggro
When it comes time for Mobs to check for proximity agro, each mob passes an AABB which encloses it's aggro circle to the query interface. From the Mobs returned, we compare the absolute distance and factions as per normal.

-- Visibility
The client will query() at a fixed interval and provide an AABB which encloses it's 'visibility circle'. From the list of Mobs returned we check if any were added or removed (list diff, twice). If a Mob was added, the client gets a SPAWN_PACKET or if removed, DESPAWN_PACKET. When it comes time to update the client with new Mob positions, we only send packets for the mobs on their visibility list.

-- Important Notes
- Each time a Mob (Client or NPC) moves, they will need to update their position in the quadtree.
- Just before a mob checks for proximity aggro, they will need to update their AABB.

Comments? Suggestions?