Hehe, I've been through this idea so many times I should really write a paper on it
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Okay, for an RPG, you need a really flexible system, because ideally, each character will have an inventory too, and you don't really want a big clunky inventory system that will do nothing but hamper your progress, so I suggest the following.
Firstly, you need an array for the position of each item. Like you'd have Item_x(n) and Item_z(n), maybe Item_y(n) too if your working on a 3D map. You would use this for positioning your items too, so if the inventory changes, you'd update the position of each item object, and hide any object that is in someones inventory. You would have several other item arrays, like the quantity of a particular item, a description - and if your brave, a properties string. The properties string would be used to tell your engine what the item does, so a key might have the property string 'KEY
OOR4', then you'd parse this string when using the item, or if you use an item that replenishes health, it might look like 'H+10:QTY-1', like Health+10, and reduce quantity, this would allow for magic items that don't deplete too, it's really a matter of how much you want to do with the parser.
Anyway, let's say you have 100 items, and their locations stored in arrays and descriptions etc etc. The whole idea is that you store the inventory of every character inside the arrays, so each item is unique and can only be in one place at a time. You would use a negative number on one of the locations to denote that it's in an inventory. To be sure that your following this, I'll give an example.
Item 1, a key at location x100,y0,z100
Say your player, character 1 was at the same location and wanted to collect the key, you'd set the location to x-1,y1,z-1, so x-1 means that it's in an inventory now, and y1 means it's in character 1's inventory.
Now the player walks to position x32,y0,z32 and drops the key - you'd simply set the location to the players location, and that's it back out of the inventory and on the ground again. If there was a thief nearby (lets call him character 15), he might want it - so he'd walk over and collect it in the same way, x-1,y15,z-1 becomes the new location of the key.
Once items are used, you can set the location to an abyss, like x-10000,y-10000,z-10000 - the chances are that your engine would miss these items anyway, but it's a good way to avoid annoying code because it's all done with arrays. Items could be moved around really easily, swapped for other items etc etc - once you have the system in place the world is your lobster.
Despite really easy inventory management, you can use the same system for viewing the inventory, viewing other character inventory, swapping items - everything to do with inventory can be done really easily with this system, including collision detection, physics, gravity - all with minimal, easy coding. You'd simply loop through your items when you have to, and update those that are not in an inventory, perhaps even have a trigger for when items are on the ground, that way if you wanted gravity, you could do something like:
* Drop item, so location is set to character location, and Y is set to character location plus drop height. An extra array, Item_falling(n) is set to 1, this is the fall rate.
* For every item with a fall rate that isn't 0, you'd increase the fall rate and adjust the Y position.
* When it hit's the ground set it's fall rate to 0.
Doing it this way will mean less lag, because it'd only be updating exactly what items it has to. You could even throw items if you had an X and Z speed array, so a character could go up a tower and throw an item out of the window to another character on the ground, still with fairly easy handling.
HTH.
Van-B
