Quick question unrelated to grids but related to the map itself. Using EUDs to find the mouse location should cause desync in multiplayer, if what I read on the forums is correct. Are we to assume that this is a single player map? If it is played in single player mode, constantly center viewing will also cause the mouse to move to the center of the screen. Is this then limited to a single player map played on Battle.net or LAN?
Now back on topic. I apologize if this still is already known or said before; if it is, please ignore the blabbering newb that is me.
Coordinate Grids won't lag like Mobile Grids will as it doesn't use create/give/remove. They also aren't limited by other units being in the way. You can create a Coordinate Grid system with 1x1 accuracy in a little over 128 locations through the use of units to represent an axis. It was done in FRAGs.
For example, say I have a 30x30 coordinate grid. Along the top edge of the map, I pre-place a row of 30 units in this repeating sequence; Zergling Hydralisk Marine Medic Zealot. For every group of these units, I have a 5x1 location called Group X over them, where X is a number from 1-6. I also have a row of Spider Mines along the bottom edge of the map.
Now say I want to create an Archon at position (14, 7). I'll subtract 5 from 14 until I get a number between 1 and 5. The number of subtractions +1 (in this case 2+1=3) becomes which Group I should pick from (the location called Group 3). The remaining number (in this case 4) becomes which unit to center on (which is the Medic). Now, I center a 1x14 location (to get Y coordinate 7) on the Medic located in location Group 3 and create an Archon in that 1x14 location.
If I want to create the Archon at position (14, 25), a similar process is used. After finding that I need to center on the Medic in location Group 3, I center a 1x30 location on the Medic, then center a 1x10 location on the Spider Mine located in location 1x30, then create the Archon in the 1x10 location.
In other words, the Zergling represented 1, the Hydralisk 2, the Marine 3, the Medic 4, and the Zealot 5. The Groups represent a form of multiplication to save locations. 14 = 5 + 5 + 4, so I need to get the 3rd group, 4th unit.
Though it would take more triggers to do, it is also possible to not use groups at all (saving even more locations) but instead use every single unit possible owned by different players (computer players and players 9-12). A Zergling owned by player 9 might represent 1, another owned by player 10 might represent 2, and so on.
Note that there is a drawback in that as you're using units, you may actually approach the unit limit. The 30x30 example used 60 units. Also note that you could also use the Y axis first, whereby the units would appear on the left and right side of the map instead.
On a 256x256 map, using 16 groups of 16 different units, a total of 128 + 16 = 144 locations used. If no groups are used, only 128 locations are needed, though it would inevitably involve far more triggers. Furthermore, this will require 512 units to be delegated specifically for the grid itself, 256 for the top row and 256 for the bottom row.
Basically, the Coordinate Grid is definitely usable with 1x1 accuracy on a 256x256 map. It has advantages over Mobile Grids (no lag, no units getting in the way) and disadvantages (requires 512 units and 128 locations). Use what you feel is most applicable to your map.
Whew, there's my 2 cents on location saving for Coordinate Grids. Forgive me if you've heard it all before.
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