# Coherence between 2d tile maps

In dwarf fortress, there are 3 levels of maps in the screen you pick your starting position, and they all coincide with each other perfectly. I am assuming that the top level tile accounts for lets say 36 smaller map blocks, and when the player spawns on the map, that is just a noise value at a different level or frequency of even more tiles.

The selection screen looks like this:

How is such a level of coherence achieved? It doesn't seem like simply adjusting noise frequency/octave values would work perfectly, or maybe it does, I am just not grasping the workflow properly?

• It sounds like you're describing a level-of-detail (LoD) system, where you represent your terrain at multiple different densities depending on how close the player is viewing it. I'd recommend putting that in your question title, so it's clear what you mean by "proper" – DMGregory Sep 3 '18 at 13:38
• Hi I updated my question as the original was very poorly worded – LAdams87 Sep 3 '18 at 14:59
• Can you explain how you currently envision the octave adjustment and why you think it wouldn't work? – DMGregory Sep 3 '18 at 15:01
• So if we have a heat map that makes up a world with land and oceans, if the user clicks a tile and we teleport down to that tile, how do I accurately fill the new tile group (which is now prob a 36x36) from my noise sample to represent a ground level interpretation of the heat map? – LAdams87 Sep 3 '18 at 17:10

• @LAdams87, actually I suspect TurtleKwitty is exactly correct. I imagine the most detailed possible level is generated first and probably divided into Chunks (similar to Minecraft). Each Chunk is given an average representation, and possibly grouped into a lower LOD Chunk, which is then also given a representation. Working from most detail to least is the only feasible way for this to occur, and since those chunks are accurate when moved between, it makes the most sense. – Jesse Williams Oct 9 '18 at 14:15
• Don't confuse graphical detail and LOD (because "they are 2D tiles") with actual detail LOD, where the detail on the tile lives. A 9x9 char array has more detail than a single character, but could be represented, on average, by a single char at a lower level of detail (higher zoom out). – Jesse Williams Oct 9 '18 at 14:17