Vast topic: How are sims simulated? (Age, wealth, education...)

[Cool_Z 1,547]

Good day everyone!

I have become curious about how the simulation was working in SC4.
Of course I know that unlike Skylines, Sims in 4 are simulated only in "presence", but how?

I'm also cursious about health, wealth and education. Is it just a global percentage applied to groups of population in map areas or is it more precise?
Do Sims get wealthier? Do Sims really age?

I am wondering what the underlying mechanics are, do we have a full documentation about that somewhere or are we just guessing by observing what happens ingame?

[Prophet42 1,503]

Those are some excellent questions.  Here are my thoughts/observations.  Others with more knowledge of the simulator can add/correct any information I may state here.

Basically the simulator does not simulate individual Sims. It uses what are called 'Tracts'.  From  the Prima Official SimCity 4 Deluxe Guide: 'A tract is a chunk of land used by the simulator to evaluate a location. The dimensions of these tracts depends on the purpose for which the simulation is using them'.

A tract of land can include any number of lots and/or utility buildings for the simulator to evaluate (this may include a portion of the city's residents).

Now if you go into the Simcity_1.dat file, you will find an exemplar called 'Residential Simulator'.  Within the Residential Simulator you will find all sorts of configurations, settings, calculations...etc. that use a tract of land for the calculations.  Stuff like 'Death's door HQ', 'EQ reset percent', 'Water Pollution to HQ Decay Curve', etc...

So to answer some of your questions

Education and Health are applied to tracts of land.  The simulator will sum all the tracts and average them to come up with a city's EQ and HQ.

Sims do age, but only in the context of a tract of land.

Sims do get wealthier, but again only in the context of a tract of land.

Now as a side note, if you plop a MySim into a city, you can watch that Sim grow old, get wealthier, get smarter.  However, this is done by using the city's 'potential' (the average EQ and HQ), and if the Sim is within the radius of a school and/or hospital.  For example, if you start a MySim as poor, the city has a High EQ and HQ, and the Sim is within the radius of a school and hospital, the sim will quickly move up to high Wealth, Education, and Health.  However, if they are in a tract of land that does not have access to education or hospitals, then the Sim will stay poor and die young, only being able to obtain to the averages of the city.

 

[Cool_Z 1,547]

Hmmmm.... so in the case of wealth, it's the land that gets wealthier and it's applied to a certain number of sims according to the density?!
 

 

edit : (and the same for education, heath, etc...)

[Prophet42 1,503]

I would say your statement is correct.  Within the tract of land are the lots.  The lots are what contain the buildings and the sims living in them.  I believe the simulator will determine the wealth of the building on the lot depending on demand and desirability among other factors.  The sims living in the building take on the wealth of the building.  This is also true if the building downgrades.  For example if a high wealth building downgrades to medium wealth, all the high wealth sims 'move out' and medium wealth sims 'move in'.  In essence, the simulator re-classifies the sims and changes the averages for that tract of land accordingly.

[Cool_Z 1,547]

So there no "solid" position for sims.

I thougth SC4 had part of that by populating the buildings, and then applying changes to the group of sims inside it. Not going as far as taking each sim into account but still considering the sims in a building as a separate group.
It is really fully statistical.

[Prophet42 1,503]

 You have to remember that back in 2003, when SC4 came out, computers did not have enough CPU power to simulate a lot of interacting entities.  Even with using a statistical approach, SC4 put a lot of strain on computers back in it's day.  There is a lot going on under the SC4 hood.

[Cool_Z 1,547]

Yep I'm fully aware of that (I bought SC4 at release... and yep it was demanding... and still is because it can use just one core).
But is that approach really less calculations-demanding?

Also... I still marvel at how alive SC4 feels. The cities "breathe" and react like a living being.

[twalsh102 1,601]

This speaks much to how ingenious the creators of SC4 really were.  So with the game as it currently exists, the game keeps track of "tracts" and everything in them (zoning, types of buildings, number of Sims residing or working in the tract, health, wealth, crime, etc).  But there is a finite number of tracts in each city square to keep track of.  Everything is just statistics that get recalculated on a regular basis.

The other alternative would be an agent-based simulation, which would have been impossible with the common hardware available when SC4 was created.  With an agent-based game, every object (Sim, vehicle, building, tree, bird, resources, etc.) is an agent that must be tracked, along with the attributes/behavior of each object as they might change throughout the game.  If someone were to try and combine the agent-based game engine of something similar to Cities: Skylines (while eliminating all the limitations it imposes), with the vast scope that we see in SC4, everyone would probably need a gaming computer that has quad 8-core CPUs, 512 GB of RAM, and octuplet SLI or Crossfire GPUs in order to run the game at a reasonable speed (being facetious here, but the hardware requirements would most likely be beyond the financial means of most game players:  "Hey Mom, I found this neat new game that I just have to have.  I'll even pay for it out of my allowance.  I'll need a new computer though!  I found one online that meets the minimum requirements for the game, and only costs about $8,000."

[Cool_Z 1,547]

Well... you can sell a kidney, you don't need both. 

[twalsh102 1,601]

Oh, No!  That involves hospitals and pain. 

I'd probably try the slightly less painful route of "Hey Mom, if you buy me this, I'll consider it my birthday and Christmas presents for the next few years, and you can buy me a less expensive car when I graduate!  I'll even apply to less expensive colleges!"

[MatlockMan 370]

I'll be honest and say I prefer SC4's simulation of population over C:SL's. The former does a better job of allowing big cities to be viable and still feel alive, while the latter is just frustrating with its 1 million limit. 

[jeffryfisher 2,176]

23 hours ago, Prophet42 said:

Education and Health are applied to tracts of land.  The simulator will sum all the tracts and average them to come up with a city's EQ and HQ.

Sims do age, but only in the context of a tract of land.

Sims do get wealthier, but again only in the context of a tract of land.

So sims are bound to the land... We should call them serfs instead, call the tracts "fiefs", and then a "city" becomes a barony. So instead of holding the title of "mayor", a player should be called a "baron".

[madhatter106 3,911]

Hopefully not via Glass Box...

[matias93 7,535]

Does somebody talked about a glass box with sim serfs on it?

 

[CorinaMarie 29,852]

I decided to toss together my observations with a handful of pictures.  We've all peeked at the Resident Avg Age data view and it ranges from bright green for young Sims to dark blue for elderly ones. To get the oldest aged Sims they need health coverage, breathable air, and clean water to drink. Crime may or may not play a factor in their longevity too. In one of my city tiles in my Corillion region I created a very dirty industrial complex. Many Low wealth Sims live in two Large Tenements in the center of the area.

In this screenshot I've run the simulation for about 100 years making no changes so everything could stabilize as best it could.

^ This is the Resident Avg Age overlay and I've Queried the Elementary School to the left of the first tower. We can see 206 young students in year 647. (Not pictured is the High School query which has 20 students atm.)

 

Here we have the Health overlay and the Query is on the Medical Clinic located between the towers.

^ We see 401 patients atm.

The occupants in the towers are in constant flux:

• Left tower: 2546, 2519, 2489
• Right tower: 2403, 2434, 2462, 2290

Each fluctuates between those numbers at various times of the game year. It is not for a lack of jobs. Air and water pollution means some Sims get fed up and move out then a little while later others move in. Those incoming Sims have a starting lifespan of 60 years. If there were no health coverage it would decline to 50 years as the Sims are slowly poisoned.

 

Here's the Air Pollution:

 

And the water pollution:

 

So, now I plopped 5 MCP Water and Air Purification Plants (which I've tweaked to not age degrade).

^ Interim pic while they do their thing.

 

A few months later the air pollution is almost all gone:

 

And the same for the water pollution:

 

With the better environment some more Sims moved into the towers which means there are more students in the Elementary School:

 

And this also means more patients for the Medical Clinic:

 

Air pollution overlay:

 

Water pollution overlay:

 

A few years later both towers have stabilized their occupant numbers to 2674 and 2689 respectively. They do not vary from these building population numbers for the rest of the test.

Seven years later and we see the Resident Avg Age is turning a darker green and there are less Elementary Students (185 now).

 

85 young students in year 659:

 

64 the next year:

 

And by year 661 we are up to 296 High School Students:

 

Year 662 with 24 Elementary students:

 

Year 669 and 7 grade school students:

 

And eventually only one single young student and the Resident Avg Age is trending towards the darker blue:

 

So, it seems to me that absolute unchanging population in a given building is essential to having old age residents (along with a good environment and nearby doctors). As long as I don't make any changes to upset the Sims living in these two towers the average age will stay high and the number of grade school students will never rise above single digits again. See my next post where I let this run much longer. The Sims will eventually reincarnate.

[jeffryfisher 2,176]

19 hours ago, CorinaMarie said:

As long as I don't make any changes to upset the Sims living in these two towers the average age will stay high and the number of grade school students will never rise above single digits again.

They don't die off and repeat the oscillation with reincarnations?

[CorinaMarie 29,852]

39 minutes ago, jeffryfisher said:

They don't die off and repeat the oscillation with reincarnations?

Good question. Turns out I didn't let it run enough.

 

Here's the Elementary School with 1 student in year 720:

 

High School in year 720 with 42 students:

 

After the reincarnation there are 23 Elementary School kids:

 

And 304 High Schoolers:

 

[Cool_Z 1,547]

Amazing! So you can really follow the aging process. Great job you did.

[CorinaMarie 29,852]

58 minutes ago, Cool_Z said:

Amazing! So you can really follow the aging process.

Yep.

The key seems to be that the buildings you are watching are 100% stable with no Sims moving in or out. Otherwise they stay in the green age category in the data overview (which makes sense as the average age goes down when new Sims are moving in all the time).