Let me start off by saying that I don't know very much about this game (yet); I've put it in the cooler a few years back, because shortly after buying it the (then still) Mondoids came out showing off the animation system and I didn't want to burn myself out before it released (this isn't a criticism; I'm a patient man & I've seen the countless other improvements in the Thurdoids, but after seeing the animations I couldn't unsee and boy was it worth the wait! I'm hooked and went from 7 hours in the game to 30+ since the update). After thoroughly enjoying a couple of runs in the standard Survivor mode, I've felt that the setting didn't really match with the character I wanted to roleplay and I began looking in to the Custom Sandbox mode.
Which brings us to the main point of this post; the lack of information (or misinformation in some cases) I could find on some of the vague terms used in some of the tooltips. For instance what are "Cells" and "Chunks"? What exactly does "Unseen" mean? How do the zombie respawn options function in conjunction with eachother? So I did some testing and thought I'd share the results, since in my search for answers on these questions I've seen quite a few others who'd want a similar experience as myself (slower build up of the zombie apocalypse) but ended up with a ghost town (as did I before these tests).
Let's start defining some terms:
(this is an image of the Zombie Population mini-map you can pull up when you're running in Debug mode (add -debug to your launch options); there'll be more of these)
Cell (300*300 tiles): the larger square with the numbers in the top left that indicate actual zombies (445), desired amount of zombies for the Cell (889) and the respawn timer for the Cell (72.0) respectively.
Chunk (175*175 tiles): the brighter white smaller square; you're always centered in it and thus it moves with you across the map. Now technically this could be your potential max vision cone and chunks are actually smaller pieces of the map (I've read someone saying Chunks are 10*10 tiles), but since it doesn't matter if you actually see the chunks for the system to determine whether or not to spawn zombies (which I'll illustrate in a moment) you might as well consider this 'your' Chunk.
Respawn Hours: This sets the timer of the Cells that are eligible to spawn zombies (as far as I could tell it always starts running when the Cell has about 10 more desired amount of zombies than actual zombies). Now in the image above the Respawn Hours timer is frozen at 72.0 even though there's only about half of the desired amount of zombies; I suspect this is due to zombies being drawn away to other cells by meta-events or player activity but they still belong to this Cell.
Respawn Unseen Hours: Everything your chunk has touched won't respawn zombies until this amount of in-game hours has passed outside of your chunk. Remember that the Respawn Hours timer for the Cell also has to fire to spawn zombies. For example: in the images below I have Respawn Unseen Hours at 3 and Respawn Hours at 1; in the left picture the Respawn Hours timer is about to fire, to the right is a fragment later when it did. No zombies spawned, because I did a quick lap where my Chunk covered the entire cell.
Because this was done at night time (limited visibility) and the purple numbers represent cars you haven't spotted with your vision (when you actually spot them the number turns blue) I'm fairly certain that it doesn't matter if Chunks are actually smaller pieces, you're better off regarding the 175*175 box as 'your chunk'.
This is what it looks like when I've only covered half a Cell with my Chunk; all the zombies spawned in the bottom part of the Cell in the blue box (was a different test so in this case the Respawn Hours is 4 and the Spawn Multplier 0.5).
For the sake of completion I've added these options as well even though they're pretty self-explanatory:
Spawn Multplier: This sets the fraction of a Cell's desired amount of zombies that may respawn when the Respawn Hours timer for a Cell fires. In the example below it's set at the default 0.1 or 10%; it's not entirely accurate in all the cells (I've turned off meta-events and I was a ghost (-debug cheat) standing still, so maybe a couple of random zombies near the borders decided to wander in or the math is a bit funky). Also, minor gripe, fix the typo
Population Multiplier: This sets the default amount of zombies on which the Population Start/Peak Multipliers act. I'll illustrate with yet again some more Zombie Population maps:
Population Multiplier = 1.0; Population Start Multiplier = 4.0; Population Peak Multiplier = 1.0 and Population Peak Day = 5
Population Multiplier = 4.0; Population Start Multiplier = 1.0; Population Peak Multiplier = 1.0 and Population Peak Day = 5
Population Multiplier = 4.0; Population Start Multiplier = 1.0; Population Peak Multiplier = 2.0 and Population Peak Day = 5
Population Multiplier = 4.0; Population Start Multiplier = 1.0; Population Peak Multiplier = 0.1 and Population Peak Day = 5
Again the math is not exact in these examples, I think the desired amount of zombies for a Cell is randomly generated in the vicinity of a set number for that Cell and it then starts to build up gradually towards the Population Peak Multiplier (e.g. if a Cell's set number is 100 and it generates 90 for desired amount of zombies it'll then start to climb to 180 on Peak Day if you've set the Peak Multiplier at 2.0). This might also be what's happening to the respawning; if you have a Respawn Multiplier of 0.1 and the Cell's desired amount of zombies is 100 it might spawn for example 8 or 14 instead of the perfect 10 you'd expect.
Population Peak Day: Besides determing the day the maximum amount of desired zombies reaches it's peak in conjunction with the Population Multiplier it apparently also plays a role in determining the amount of desired zombies at the start. Below is the result of Population Multiplier = 4.0; Population Start Multiplier = 0.0; Population Peak Multiplier = 4.0; Population Peak Day = 365 (it's not the Population Start Multiplier at 0.0 that causes this few; I've tried it at 0.0 with Peak Day at 5 and the Cells in the left column will have ~500-600ish desired amount of zombies at the start) and for the fun of it I've let it play out as you see in the other images (I wanted to do the end result at 1 year too, but halfway the 8th month the game crashed, which is understandable because that amount of zombies is insane and I'm breaking the game's balls by having Respawn Hours at 0.01 and going at 1000 speed with the maximum amount of desired zombie acceleration possible, it would probably be at 12k)).
One interesthing thing that I noticed is that the spawning didn't start until somewhere after 4 days and then it spawned them all (Respawn Multiplier = 0.1), before this snapshot the actual zombies remained at 2,0 2,0 (like in the first image) even though the Respawn Hours timers kept firing and the desired amount of zombies was way above the actual ones. It was also drawing the green lines, which I assume indicates the cells where the zombies get pulled from and where they're placed (if that's true it might explain the difficulties of spawning zombies when the desired amount of zombies is very low in the beginning: the other cells have no zombies to pull them in).
I've also noticed that sometimes you need to "kickstart" the spawning process by manually initiating the first spawn, I'm guessing this is because I've done most of these test standing still in a closet, not actually exploring other cells and when the Respawn Hours timer fires it doesn't know what cells to pull from, but by doing it manually (right click a cell and select Spawn Now, see image below) it brute forces the game to get the information of cells I haven't seen (which it wouldn't do normally during the game because of performance reasons I presume). After the "Kickstart" the spawning process works as intended: everytime the Respawn Hours timer fires new zombies get pulled from other cells and placed in to the cell that's spawning them. With an extremely low starting desired amount of zombies (as in the ridiculous example above) the "kickstart" won't work because I think there's not enough zombies in the cells it wants to pull from.
Now with all this information I thought I had a pretty good idea on how I intended to create a scenario where the apocalypse starts off slowly and relatively quickly ramps up, without ending up with a ghost town, but I've only just discovered that your Population Peak Date also plays a role in the amount of starting zombies and I need to do some more testing to finetune these settings to where I'm kind of happy with how quickly it ramps up.
What I do know is that however you set your parameters, there are some restrictions to make sure zombies are spawning in quickly. For instance: you can't have a gradual (and non-ghost town) build up if you also want to eventually clear large parts of the map for extended periods of time, because you need a low Respawn Hours timer for the initial spawns to fire, if you set this to high you're guaranteed no spawns until at least that amount of hours + the time it takes for the desired amount of zombies to reach the point where a cell is eligible to respawn.
Which brings me to the next restriction: moving around to much. You need the low Respawn Hours timer to avoid Ghost-townism and playing in a world where you can hardly make a dent because things keep respawning wouldn't be too much fun either. So what you do want is a reasonably high Respawn Unseen Hours so you can clear a couple of cells for a bit of time without being overrun by the quick spawning of a low Respawn Hours timer. I'm thinking I'll probably end up with something ranging between 48-96 hours for Respawn Unseen and somewhere around 4-12 for Respawn Hours, I think this will allow me to maintain a decent ramp up of zombies early on and still be able to clear cells and prevent the respawns for a few days. Another thing to keep in mind and why you can't move around too much in the beginning is that you'll also spawn zombies (e.g. the ones in buildings) with your Chunk that counts towards the cell's actual zombie number, so even if the cell was eligible to respawn and the Respawn Hours timer was running, if at any point you spawn enough zombies to make the cell non-eligible the timer will reset until it's eligible again. Now this doesn't matter too much when the zombie numbers are eventually high enough or when most cells are maxed out when you enter them for the first time later in the game, but when the desired amount of zombies is low enough to get that 'everything is fine' start to 'holy crap it's the zombocalypse' by day 4-5, you really don't want to prevent your surrounding cells from respawning. Not by doing this and also by not moving around so much that you cover entire Cells with your Chunk regularly causing the Respawn Unseen Hours to block the respawns from actually happening when the Respawn Hours timer fires. Ideally I guess you want to be in the middle of two Cells that have a relatively low desired amount of zombies (regardless of Population Multiplier, some cells are logically just designed to be more or less crowded). This way you can move about a little bit to all sides and not spawn too many zombies with your Chunk in neighbouring Cells or cover an entire Cell preventing respawns from firing.
The house I've used in most of these tests is actually pretty good for what I was looking for and it's a house you can spawn in with the key too. I can make my way up to Cortman Medical and the store next door with a desired amount of zombies low enough that I only meet a zombie or two I can avoid and wave away as drunks or crackheads (for my immersion!), find it a bit weird that the store owner is not there when I wanted to buy a couple of Cornettos, but no big deal I'll leave some cash on the counter and return home to study for my final exams (because the guy I wanted to roleplay that started this whole series of experiments is a highschool student whose parents left him home alone because they had to take care of grandmother in Westpoint that called to complain about an illness she was coming down with (what could it be??)) This gives him a motive to be oblivious and homebound, because I'm studying my for my Biology (First-Aid for beginners), Physics (Electronics/Mechanics for beginners) and Home-Ec exams (Cooking/Carpentry for beginners), and also a motive to try to find a way to reach grandmother's house and find out what happened to her and his parents when he eventually realizes what's going on.)
I'm also realizing now that this is becoming more and more of a niche that works only for phreak roleplayers such as myself who're content to use the time spent playing a somewhat boring version of the Sims coming up with the backstory and possible routes the character could take. If you want a slow build up and move around a lot you'll just end up stagnating all the cells in the vicinity from respawning zombies and be left with a ghost town, unless you leave those cells behind after a while the necessary high Respawn Unseen Hours will keep preventing respawns from firing. Which brings me to the last legs of this post that went off the rails a little, a couple of suggestions (I will also use this as a flimsy excuse to re-post this in Suggestions if it gets buried in General Discussion).
More options to give us more control over ramp up/ramp down of the apocalypse that doesn't restrict the player to be pretty much housebound for the first couple of days or prevent those who do eventually want to kill all the zombies. Some solutions I have to make this happen are, I think, doable to implement. For example: Quarter/Half/Threequarter Population Day: this sets the days where the desired amount of zombies of a cell is at 1/4, 1/2 and 3/4 of Peak Population. This allows for a bit more control over how you can ramp up, if we could get Multipliers for those settings as well even moreso. Even if we could just get a Half Population Day and Multiplier you'll have much more control; you could ramp up faster by having a high Population Multiplier, a low Half Population Day and high Half Population Multiplier, but not end up in ridiculous town by having a super low Population Peak Multiplier. For example: Pop. Mult.=1; Pop Start Mult.=0.01; Half Pop. Mult.=4; Half Pop. Day =1; Pop. Peak Mult.=1.5; Pop. Peak Day =10. Now let's say that a cell has a value of 500 desired amount of zombies @ Pop. Mult.=1 and we disregard the slight random shennanigans, this is what'll happen: the cell will start with 5 actual zombies and 5 desired amount of zombies that will quickly ramp up to 2000 desired the next day. At Peak Zombie day the amount of desired zombies will have declined to 750, now whether or not you end up with something like 1200/750 or 650/750 is dependent on the Respawn Hours, Spawn Multiplier and how many zombies you've spawned with your chunk and your activity drawing zombies and meta-events. I'm pretty sure I can fiddle with all the settings to create a comfortable ramp up and optionally a ramp down if only a Half Population Day and Multiplier were added as options. This also eleviates a bit of movement restriction since the rapid increase in desired amount of zombies makes it unlikely that the zombies you spawn or get drawn in to the cell by meta-events/noise freeze up the Respawn Hours timer.
That leaves us with the other issue that restricts movement and that is the Respawn Unseen Hours and how easy it is to cover an entire cell with your chunk, setting this too high you'll end up blocking entire cells from respawning zombies for a long time and setting it too low will make you feel like you're never making a dent. You could (if you implement the Half Population Multiplier & Day) fiddle around with the settings and have a ramp up/ramp down where you'll still have to murder thousands of zombies but eventually end up virtually cleaning out the map, but this will also take away some of the ramp up acceleration control. A better solution would be to have an option like Ignore Respawn Unseen Hours, which will set the amount of hours (preferably with a high threshold) the game will ignore the Respawn Unseen Hours setting and still spawn zombies even if you've covered it completely with your chunk. You could set this pretty high so the game will keep spawning zombies at the start until this timer expires and from there on out you're able to clean out parts of the map for months if you've set Respawn Unseen Hours also pretty high. You even get more control over how steep you want the zombie population to ramp, because this'll allow you to have a higher values for Respawn Hours without you repeatedly resetting it over and over causing Ghost-townism. I reckon this would be a little harder to implement.
Some other things that I wouldn't mind seeing is an option or set of options to set what kind of cars and loot you want spawned after x days. So I can set how I want the spawning to be handled at the start (e.g. Abundant loot and High quality cars but Very Often locked) pretty much as you do now, but in a column next to it are the same options, but you can define after how many days the game will use these (e.g. After 14 days Very Rare loot and Crap quality cars that are Rarely locked). If I understand correctly loot gets spawned as soon as your chunk touches the places that can contain loot, it should be possible for the parameters to change on the fly so that the new loot you discover will follow those rules after the amount of days you've set. I guess you could cheese it by plastering your chunk all over the place causing as much of the abundant loot and good cars to spawn, but if that's how you play this whole attempt to create an immersive experience for those seeking a more gradual roll in to the zombocolypse is not for you anyway.
tl;dr: This stuff is complicated, I'm a verbose motherf'er (sorry) and I tried to be as clear as possible to avoid confusion even though I'm aware that it's probably still f'ing confusing at times. I also came to the realization that a lot of this might seem like way to much of a hassle to most people; even if you understood exactly everything I've rambled about, to make a more gradual ramp work for a specific situation you want to create it'll still require some testing using the Debug mode for yourself only to realize you'll either end up playing a slimmed down version of the Sims and be housebound, or be content with a ghost-townish start. Still I think some of the definitions I've given could be of value to some people experimenting or willing to experiment with the Custom Sandbox options to create their own scenario's. And I've also made some suggestions. Here's some sillyness
Population Multiplier = 4.0; Population Start Multiplier = 0.0; Population Peak Multiplier = 4.0 with a Population Peak Day = 1.0
Note that these are just idle zombies that haven't noticed me (I'm a ghost Ooo o OoO oOo (bonus points if you get the reference, double points if you know what I said, triple points because you're a hero that you've made it this far in my rambling post (cannot be redeemed if you've just scrolled to the end))