Hey!

I've done some thinking on how game levels are managed and have come to the conclussion - I'm not sure. Maybe there is a good read on the topic of handling game levels and their logic? Do all game levels consist of some kind of a tile map? As far as i know, for example, in 3D games the game worlds are split in to chunks, and only the few closest to the player are rendered and there logic processed. Am I right? What about RTS ganes in which units move all around a map? AoE2 is on my mind, also AoE3 because it's 3D.

Sorry for the late reply and thanks for the answers!
I was mainly interested in 2D isometric games, because I'm slowly building the engine. I just was thinking about how other games take care of the logic and the rendering. If for example I have a large map, it would be silly to go through all of the game objects currently present to check if I need to render them, or no? That's why I was thinking of AoE or any other RTS game.

At the momment i have come up with the following: the game level is made of a 2D array of tile-objects, which have all kinds of properties. I just could create a sub list of objects on screen from looking at which tile the player is. The same for game logic, as I dont need to simulate what's hapening too far away. Also, would it be good if a tile knew what was on it? A mere pointer.

Another thing, in a game like Skyrim, it seems that some NPC's are doing something when I'm not there.. How do they accomplish that? Or is it just hardcoded where one should be at a given time?

Sorry for the late reply and thanks for the answers!
I was mainly interested in 2D isometric games, because I'm slowly building the engine. I just was thinking about how other games take care of the logic and the rendering. If for example I have a large map, it would be silly to go through all of the game objects currently present to check if I need to render them, or no? That's why I was thinking of AoE or any other RTS game.

At the momment i have come up with the following: the game level is made of a 2D array of tile-objects, which have all kinds of properties. I just could create a sub list of objects on screen from looking at which tile the player is. The same for game logic, as I dont need to simulate what's hapening too far away. Also, would it be good if a tile knew what was on it? A mere pointer.

Another thing, in a game like Skyrim, it seems that some NPC's are doing something when I'm not there.. How do they accomplish that? Or is it just hardcoded where one should be at a given time?

Just because you don't need to render an object, does not mean that you don't need to simulate it's behavior. This is where separating logic falls into play. Your rendering methods should only render what is visible, but your update methods should update all entities on the map in an RTS style game.

rather than looking through each tile to see if it is visible, then adding each object on the tile to the renderable list, why not just check against each entity in the game and see if it is within a certain distance of the player. Usually you will have more tiles than entities, and this should be a faster method.

I've not played skyrim, but I would assume that they use some kind of quest table that uses boolean values to identify key events in the game, such as whether the player has killed some monster, or spoken to some character. The game logic can use this table to decide what should happen to NPCs. Say for instance, you save a villager just outside town. when the battle is over, the quest table is updated to reflect that jimmy two shoes has been saved, which starts a script that gets jimmy to tell the players that his family has been taken by a monster in a cave, and then lead the players to the cave. When cavemonster is dead, the quest table is updated, and a script now puts jimmy and his family back in the town, so that next time you arrive they can shower you with appreciation.

Depends a lot on the game in particular.

For instance in an rts you never really want game objects to stop updating because a key part of an rts is that units will always be under the implication of something might be happening to them, your band of warriors across the map might be getting attacked by ghosts while your camera is at your main base clicking create units.

In a game like skyrim you have different states objects may be in depending on distance and such. For instance when you're out in the world map the game world is split into cells, cells are loaded and unloaded based on distance around your character. However you still need to render things like the terrain, and distant mountains, the game has a system where it renders the terrain at low detail level depending on your distance to it and it starts to load and change the asset quality as you get closer, when you move a certain distance from a cell it will also unload the entities in it(small detail objects like rocks and plants and things) essentially a lot of game cells will be "dead" at any given time, as in they won't be updating any objects in them, just rendering the basics of the height map and certain large objects.

For things like the ai I'm not entirely sure how skyrim does it despite the fact I play it a lot. In oblivion they tried to sort of "patent" a new system of ai where every npc had a set routine based on time, they modified that a bit because it was really robotic always seeing the SAME conversation happen at the same exact clock time in game. My assumption based on that, is that when you enter an unloaded cell like a town it probably loads the entities and then simulates their behavior, a lot of this might be trickery and assumption. For instance a shop might restock itself automagically just as a product of time having passed. Npcs migh be moved depending on the current clock time, some randomization factor and their "schedule" so it looks like they were going about their business before you walked in, but they may not have been. They might even continue doing this behavio if you leave town but are nearby still to add a bit more realism to their movements if you enter the town again. These are all mainly guesses, but are ways you could handle it.

Using LOD and unloading chunks like that also happens in other open world games like farcry, the real meat of the behavior is based on the fact the player needs to be able to see distant things like terrain and large structures but it would be a total waste to be updating objects or actors in these far off areas if you are nowhere near them. Thats the trick of it, and that varies wildly from game to game. On some game types areas may always need to be loaded, in others they might be completely unloaded. Something like minecraft for example, when it unloads a chunk it flat out removes it and stops drawing it.

Explaining the rendering is a bit of a large topic for one thread, a lot of how to remove excess geometry in rendering depends on what tools you have for subdividing the game world(is the map split into chunks? can you use the position of the camera to cause certain areas to not be set to render?) Its a case by case thing.