Epidemic Modding

[Senna Seznec]

https://ck2.paradoxwikis.com/Disease_modding

This is really the extent of information I've found on how to modify epidemics, and it leaves me with a few questions on how to change things, so I'm going to try to summarize those questions as best I can.

1. Contagiousness. Best I can tell, this is the chance per monthly tick that the disease will spread to an adjacent province.

2. Outbreak chance. This is, presumably, the chance of an outbreak. However, this isn't exactly clear on a number of factors:
2a. When is this calculated? On what is it calculated?
2b. Does modding a new epidemic with an outbreak chance necessarily increase the chances of a disease occurring per tick? E.g. if I added ten new diseases would the world become a rainbow hell of competing diseases even on normal disease settings?

3. Can I have events interact with epidemics? Spawn them? Cancel them? Adjust them during the outbreak? I know you can set flags and check for those flags that will affect spawning and spread of epidemics and suchlike, but can I kill an epidemic with an event, or change how fast it spreads while it's currently ongoing, etc.?

I'm sure I have more questions as I work here, but that's what I have for now.

 

[Rydelfox]

For number 3, There a a few ways that events can interact with epidemics

activate_disease = <disease_name> will allow diseases that are off by default to spawn.
reduce_disease = <double> will weaken an existing epidemic in a province
spawn_disease = <disease_name> will start an epidemic in a province
start_outbreak = <disease_name> will start a epidemic using the information defined in the diseases timeperiod entries

I think reduce_disease = 1 should be able to cancel an epidemic in a province. You can't adjust the settings of a epidemic outside of changing it in the disease file

 

[Senna Seznec]

Thanks for the assistance, but if there's one question on this list I really need answered it's 2b. It could have pretty big implications for how modding diseases should be undertaken. Without an answer I'm just gonna have to test it myself.

 

[Urist_McDorf]

Thanks for the assistance, but if there's one question on this list I really need answered it's 2b. It could have pretty big implications for how modding diseases should be undertaken. Without an answer I'm just gonna have to test it myself.

For what it's worth, the basic diseases have a total (base) outbreak_chance of 0.1045 (which is weird on itself because I thought values here were limited to three numbers after the decimal point, but apparently the dancing plague begs to differ). If we treat it as percentages usually are, that means a 10,45% chance per... something. I want to say per month in the world, off-hand, but that will definitely take some more figuring out. Note that timeperiod blocks (of which a disease can have several instances) have their own outbreak_chance.

 

[Arko]

It looks like it is also related to province number. With less provinces, you get much more diseases. So it is somehow balanced for vanilla map province account.

There is also some defines to play with.

 

[Senna Seznec]

I have almost no idea what you just said, Arko.

AS for Urist (nice): Increasing the effective sum of outbreak chances from .1(mumble) to .2(mumble) doesn't sound like it would be a big problem when you put it in those numbers, but if I tell you disease happens twice as often a much bigger issue is apparent. Like, the scale may seem laughably small but it's how they made it work in practice.

As far as balancing goes, I'm honestly tempted to just argue to myself "Well, whoever would play a mod about diseases would be expecting more diseases to happen" and just not worry about it.

 

[Urist_McDorf]

I have almost no idea what you just said, Arko.

AS for Urist (nice): Increasing the effective sum of outbreak chances from .1(mumble) to .2(mumble) doesn't sound like it would be a big problem when you put it in those numbers, but if I tell you disease happens twice as often a much bigger issue is apparent. Like, the scale may seem laughably small but it's how they made it work in practice.

As far as balancing goes, I'm honestly tempted to just argue to myself "Well, whoever would play a mod about diseases would be expecting more diseases to happen" and just not worry about it.

That's probably the right approach; mods are not base game and are opt-in, so treating them as such shouldn't be a problem.