Hearts of Iron IV - 28th Development Diary - Weather & Terrain

[podcat]

Hello, and welcome to the 28th development-diary for Hearts of Iron IV. This time we talk about the things that you have the absolutely least control over in the game, and in real life. ie, Weather and Terrain.

We were not happy with the weather-system in HoI3. It was a complex simulation that tried to work as close to reality as possible. It was basically impossible to tweak to the situations we wanted (like very hot desert areas or cold winter in Russia in ’41), and players disliked it. It was a small performance hog and last but not least - all that effort was tucked away in a mapmode you had to keep checking (so most people did not). So for this iteration of the series, we decided to take an entirely different approach.

Full scripting control
Probability for each type of weather can now be scripted for each strategic region for each month, or a definable period. So for example we can get that hardcore, dirty, Russian mud everyone is craving for the months and locations where it makes sense. For modders out there we made a really nifty tool for setting up these values so its easy to tweak and work with (so when you guys make the Cats of the 4th Reich total conversion I’v been waiting for it will be easy). This means that since we can set everything ourselves we have full control over the gameplay effects we want rather than relying on a complex simulation to get it right.

There are 6 types of basic weather in the game. These directly affect air and navies and land units indirectly (we get to that)

Clear skies

Baseline weather with no modifiers. Just enjoy the sun bro ​

Light Rain

Harder to detect enemy air and navies.
Airplane attacks against ships less effective as well as ship-to-ship accuracy.
Higher risk of airplane accidents.​

Storm

A much stronger version of Light Rain.
Carrier planes won't be able to take off.
Bombers will have a hard time hitting targets.​

Snow

Harder to detect enemy air and navies.
Airplane attacks against ships less effective as well as ship-to-ship accuracy.
Higher risk of airplane accidents.​

Blizzard

A much stronger version of Snow.
Carrier planes won't be able to take off.
Bombers will have a hard time hitting targets.​

Sandstorm

Almost impossible to detect other aircraft.
Extremely high chance of airplane accidents.
Bombers won’t be able to hit targets on ground.​

Temperature
Temperature is tracked on province level and mainly affects attrition levels. If its very cold or very warm things will tend to break down a lot more often. You’ll want leaders with the Winter Specialist trait to maximize your efficiency in cold weather.

Mud and Snow (so, ok, there is a bit of simulation)
When it rains or snows we keep track of that (so we can show it on the map) but also to keep track of if it has gotten to extreme levels. Very high snow will affect unit movement speed, but Mud is going to increase attrition levels a lot as well as slow you down to a crawl. A smart player will try not to attack (as a wild example) The Soviet Union just as mud season begins or they might find a lot of their panzer divisions bogged down.

Shown on map
Since weather has such a large impact we wanted to make sure it was always visible to the player. Snow/mud and such is shown directly on the map while storm clouds and rain is in a layer above which we fade away the closer you get so as not to obscure unit movements.

Big thunder storm over Russia (sorry I did not have the reflexes to be able to catch the lightning )

Terrain
While we do quite a lot of things at the state-level, we still have terrain defined per actual province. The terrain-system is completely scriptable as in all Clausewitz games, but the terrains in Hearts of Iron IV is as follows.

Plains

Baseline terrain, so no modifiers, as everything is relative to this.​

Forest

50% added to time to move through.
20% penalty to attack.
20% smaller combat width.
10% better protection against enemy air superiority.​

Hills

50% added to time to move through.
20% penalty to attack.
33% smaller combat width
5% better protection against enemy air superiority.​

Mountains

100% added to time to move through.
40% extra attrition
66% smaller combat with
40% penalty to attack
10% better protection against enemy air superiority.​

Urban

20% added to time to move through.
30% penalty to attack​

Jungle

50% added to time to move through.
50% extra attrition
25% smaller combat with
30% penalty to attack
25% better protection against enemy air superiority.​

Marsh

100% added to time to move through.
80% extra attrition
25% smaller combat with
40% penalty to attack​

Desert

5% added to time to move through.
30% extra attrition​

Different types of battalions have either penalties or bonuses in terrain to attack, defence or movement, compared to a generic Infantry. A few examples. Cavalry has a minor -5% attack penalty in most rough terrain, while Mountaineers gets a movement bonus in hills & mountains, as well as attack and defence bonuses.

Unit-specific penalties that combine negatively with terrain penalties, creates some pretty bad situations. ie, attacking a mountain with heavy armor is NOT a good idea.

Next week, we’ll look at factions, and wargoals!

 

[podcat]

Excellent DD! How can you help protect your soldiers from the cold for example? Is there a tech to research? Also in the snow/ desert would your troops switch to the appropriate uniforms?

There is no winter clothing research as such. Thats basically common sense and player would always use perfect hindsight and not fight in winter unprepared. We are evil, so you'll need to actually gain those winter specialist traits through fighting in cold weather. No shortcuts.

As for appropriate uniforms at this point in the project I can only say "maybe" and not make promises.

Hello Podcat, several things:

1. Why go from Light Rain to Storm? Where is "middle"/"normal" Rain?
2. How is mud "generated"? After it snows a lot and suddendly temperatures get higher? After it rains a lot? After it rains a bit but hundreds of panzers come through the same sand track?
3. Mountains units in mountain: I take that the movement speed bonus (or the attack bonus) is AFTER taking into account the normal penalty for moving through mountains?. Otherwise mountain units would move faster through mountains than through plains..

1. gonna probably be renamed to Rain and Storm
2. if the area is set up as susceptible to mud that time of year and water levels over a time period is high enough mud develops. either rain or melting snow. doesnt matter if anyone has traveled over it (remember not a super complicated simulation we'll never be able to balance)
3. yes

Will there be an option to order aircraft not to take off in specific weather conditions?

There is no need. If you cant detect the enemy the plane doesnt take off and super bad weather means ppl dont really. We made this change because it was annoyign to ahve to micro when your planes shouldnt do stuff due to accident chance etc. Works pretty well.

An important thing for me is weather forecasting, If I look out of the window and see it is raining then I don't take off in my Spitfire.
I would however rely on forecasting to tell me when weather was coming, and how long it would last, and what is coming next.

Obviously in the real world, then forecasting was a bit iffy at times.

So, does the game have 'forecasting' elements to the weather, or is there a compelling reason why we would not need it in game?

There is no forecasting, as you said in the real worlds its iffy. The best forecast is still to guess same weather as its today for tomorrow. Consider weather unpredictable and your enemy (except when it isnt)

 

[podcat]

very nice DD.

2 questions:

if weather is scripted does that mean it is the same each playthrought?

question 2: about the urban terrain type. Why doesnt it have extra cover against air? hiding in buildings makes it hard to know for enemy aircraft to target you i would say.

- we script the random ranges, so no its not the same, although you CAN script the random seed for this if you make a bookmark where you want a specific weather only.
- had missed urban, added air sup reduction there too

 

[podcat]

Are these terrain and unit penalties additive or multiplicative?

almost everything in hoi4 is additive like in EU4. when it isnt its pretty clearly stated and shown in a different way

 

[podcat]

You elaborated on the russian winter and the possibility to script certain extraordinary weather conditions. Question: What about the Monsoon in SE Asia (Burma f.e.)? A prolonged period of rain with intermittent storms, making jungle warfare even more hellish than it already was? Is it possible to implement with the standard weather system or will this require scripting too?

yeah thats doable in the basic system (it was one of the major things we couldnt get to work in the old weather system)

 

[podcat]

I agree but the Japanese were able to employ such tactics against the British and obtained crushing victories versus superior forces. If I recall correctly the jungle was definitively helping the attacker.

For surprise attacks perhaps when we are talking guerrilla style stuff. in HOI4 japanese AI will probably go down the Battleplan/Infiltration route which give their troops recon bonuses (hence surprise ability to counter enemy tactics) as well as better attack ability at night to simulate US vs JAP

 

[podcat]

Thank you very much for the explanation and from my side I can say that I am happy with it

Regarding winter equipment did you see my earlier question?

My argument still hold though. No sane player will ignore winter equipment so why make it a choice? This is a gameplay thing, and has nothing to do with historicity or realism.

btw I am a bit hazy on german winter gear, but afaik it wasn't lack of gear it was weapons and ammo being prioritized first on very limited supply routes that was the issue, not that someone completely forgot that people need coats in winter. I could be wrong tho, was along time since I read up on it.

 

[podcat]

But soldiers need winter clothing anyways, hindsight or no hindsight. Just like soldiers need lighter clothing in North Africa.

Of course, all that is included in the packages of infantry equipment you produce. tougher terrain with more attrition (like in cold winter) = need more packages.

I'm sure some mod will break it down into lots of details (we must have jungle boots be separate!) but I dont think thats something the average player wants to deal with when they are busy fighting on the map.

its an abstraction for gameplays sake.

 

[podcat]

Why do this DD is stickyed ?

not sure. I also couldnt find it. we generally dont sticky things because then nobody can find it I dont want to fence with mods tho, so whoever did it can undo it unless they had good reasons

It's a threshold, as soon as you have frozen conditions you won't be able to dig in efficiently without major effort (read explosives and machinery). Now units already dug-in won't have this problem.
I'm not going to argue with you about it in a thread discussing something else and derail it so if you want to continue you're more than welcome to send me a PM and I can even point you in the direction of field manuals and reports that describes the various issues.

I know there was something I forgot. dig-in speed is slowed down a lot in extreme cold now.

 

[podcat]

Great dev diary! This game is definitely moving in the right direction.
1. A suggestion, the weather and terrain should be tweaked, especially weather, they are too similar to each other.
2. There should be traits for generals for all terrain or weather types instead of just cold areas. Like having generals who are good at fighting in deserts similar in concept to those who are good in cold areas. Or generals who are good at tactics in heavily forested areas.

1. no idea what you mean
2. there is. desert fox, ranger, hill fighter, jungle rat, mountaineers, swamp fox etc. its all groovy

 

[podcat]

I guess is it an OK approach, however it raises the following question:
Is UI able to cope with significantly increased number of various elements? In HOI the unit statistics page is useless if type of units increased from 20 to 200 since it is not scrolalble vertically.
But in Hoi 4 screenshots I see various places as well where I am not sure how will an extended list of option look like.

If you go full blackice on HOI4 you would probably want to redesign certain things to take space (such as pictures of equipment). We are using some new GUi stuff in HOI4 that should be easier for modders to expand on. Should be helpful hopefully.

 

[podcat]

Pardon if I missed/misunderstood it in the thread, but in regards to the terrain: is there differentiation between the land "shape" and its surface covering? i.e. desert hills, mountainous jungles, etc. or do you just pick one to be the dominant feature?

we pick the dominant/worst to fight in

 

[podcat]

Normal tracks are actually worthless on ice as you get very little traction and therefore simple stuff like changing the direction you're traveling in or even stopping gracefully is very hard unless the ice is rugged or covered in a thick layer of snow and then yes your tracks will chew it up. Normally though a unit crossing a river or lake on a divisional level would have timbers, branches and other types of reinforcement put on the ice if temperatures are not favourable for extended use.

We considered removing penalty in winter for rivers, but decided not to. Basically there is a lot of things that can be wrong and especially during combat so we felt penalty should still be there.