Does anyone here have any experience with using DPlay groups? I was thinking about using them in my (massively?) multiplayer space exploration game. It''s played in real-time (as opposed to being turn-based) and uses OpenGL to do 2D gfx with hardware acceleration (not that I have any. Damn those OpenGL guys wrote some fast software texture rotation functions!). I''m currently planning on dividing my game universe up into square sectors and then streaming each player updates for what is happening in the sector that he is in and the 8 adjacent sectors to his location. As the player moves from one side of the universe to another, the server would subscribe him to be notified of changes in these 9 sectors. I was thinking that I might make a DPlay group for each sector and message the players that way. The problem is, depending on how sparse the universe is (or how small the sectors are), there are probably going to be a lot of empty sectors with no subscribers. Do you think this constitutes an unconscionable amount of overhead? What do you think about the sector arrangement in general? I was thinking that by keeping the clients informed of not only what objects and players where in their field of view, but also nearby, that I could then load the needed textures and game resources in the background and have then ready to display if the player should travel through a given sector. This strikes me as a hugely scalable technique for making large universes. Any input on any of this would be great

You could always try doing dynamically sized sectors (kinda like load balancing). It will take a lot more work, but basically the idea is rather than keeping sectors a constant size, you try and keep them a constant object/player ratio. So areas of space with hardly any players may only have 2 or 3 sectors, but the same sized area of space with many players may be 12 sectors.
A possible algorithm to do this might be something like...
When a player leaves a sector increase it''s size, and decrease the size of the sector the player is entering by an equivalent amount.
This should acheive a kind of equilibrium, but problems with this may be..
If many players are constantly entering leaving sectors, the overhead of changing sector sizes may become to great.
If there is a massive concentration of players in an area it could get to the point where the sectors become so small that things will be happening close to the player that they won''t know about.
Hope that gives you some ideas.