Assetto4Seasons 4.1

Assetto Four Seasons, a weather engine

  1. fabrizio piedepesante
    First things first. Assetto4Season is not a collection of "weathers", thus you cannot choose the weather sceanrio you find more appealing. A4S is a real weather engine, leveraging on the scripting support provided by Content Manager. The aim of fo A4S is to bring realism into the weather department.
    Assetto4Seasons (A4S) uses some variables (current day of the year, time of day/night, level of humidity, track location/altitude, wind speed, air temperature and pressure) to craft the weather scenario on a per race basis. All the variables impact not only the visual experience but also track caratheristics such as the road temperature and the grip level.
    Assetto4Seasons reflects my vision of a weather engine; something powerful but at the same time easy to use, capable of crafting a credible and visually appealing race environment, predicatble at some extent but still capable of bringing some unespected suprises (just like in real racing). You'll appreciate it especially in a long championship (spanning several seasons).


    I know many want to use (or at least try) this mod in VR. Unfortunately I don't have VR so I have no idea how it looks like in such setup. Some scenarios (maybe most of them?) may not be usable.

    Key Features
    Credible Weather Engine: simulates the progression of atmospheric conditions in the atmosphere thorugh waves of air pressure, humidity and clouds; these variables in combination with local wind speed and air temperature, the current time of day and the latitude/longitude/altitude of the track, lead to the actual driving environment; the weather conditions are consistent across the day and night, across consecutive days and across close track locations.
    Fine tuned lighting design; the amount/shaping of light, as well contrast, saturation and color temperature are parametrically linked to the current weather condition (every day is different) and Sun position/declination.
    Dynamic Lighting; support for CM Dynamic Lighting feature (official release and test build), with headlights lighting designed to provide an appealing and functional result in every weather conditions both at night and day.
    24h Day/Night ; full coverage of both day and night (with stars)
    Exstensive Environmental Framework; stormy, overcast, cloudy, mostly clear and clear sky, with clouds motion and pattern and density of haze reflecting the combination of wind speed, air temperature, air pressure and humidity
    Credible Sun Path; sunrise/sunset, duration of day/night and the sun path in the sky replicate the behaviour expected for the given location for the given day of the year according to astrophysics principles.
    Track Adaptation; Road Temperature and Grip level are established in accordance to the weather conditions and race configuration (*see FAQ for more info)
    Championship support; support for custom championship (*with some limitations)
    Enhanced Wet Track support; when a wet track is selected the mod will automatically craft a stormy or foggy scenario (depending on the windspeed)
    Compatibility; this mod is 100% compatible with any other mod (see FAQ)
    5.0.0 - date to be defined


    In the archive (.rar) you will find 9 folders which correspond to the current release of the Assetto4Seasons.
    1 folder provides the A4S fuctionalities in QUICK RACE menu and the other 8 folders provide the A4S functionalities for setting up a CHAMPIONSHIP (see also update 6 changelog).

    More video will come. Consider that the mod allows hundreds of different sceanrios, and a video for each variation is simply not feasible. Anyway, below few videos of the Mod in action.


    Be sure to have installed the lates release of Content Manger and latest release of Dynamic Lighting Shader Add-on (the latest official release at, the test build on the Discord channel), then:
    - Dowload the archive
    - If coming from a previous A4S release delete the previous A4S folders (you may decide to make a backup to be on the safe side)
    - Extract the content of the archive on your PC and open the folder ("DL 1.22" or "DL 1.23") that applies to the version of Dynamic Lighting Shader you have installed
    - copy and paste the content of the selected folder into "/assettocorsa/content/weather" directory of Assetto Corsa, and, if prompted, overwrtite.

    That's it.


    Select the track, your car and your opponents, then:
    - Select the "4 Seasons" from the "WEATHER" menu under the "A4S" dropdownlist
    - Select the time of day/night from the time slidebar
    - Select the day of the year
    - Select the air temperature
    - Select the wind speed
    - Race!

    When setting up a CHAMPIONSHIP:
    Wwhen configuring a "round" in the Custom Championship menu in the time frame 8-18, select the "<Season> - CHAMPIONSHIP DAYTIME" of your choice, set the time of race and then the other parameters, then save.
    - when configuring a "round" after 6pm (18), select the "<Season> - CHAMPIONSHIP NIGHTIME" of your choice, set the race time with 11 hours offset; in other words if you want to run at 20:00 please set the time at 9 (since 9+11 = 20 = 8 p.m.), if you want to run at 4 a.m then set the time at 17 (since 17 + 11 = 24 +4 = 4 a.m.). Then set the other parameters and save.
    Let's make an example of a short 3 races championship happening between August and July.
    Let's imagine I want to race at:
    - Imola (ITA) at 14:00, where it is summer
    - Yas Marina (UAE) at 20:00, where it is summer
    - Bathurst (AUS) at 22:00, where it is winter
    This is I would setup the championship:
    ROUND 1
    TIME: 14
    ROUND 2
    TIME: 9 (11+9=20)
    ROUND 3
    TIME: 13 (13+9=22)

    Hope you will enjoy.

    Does this mod impact performances?

    Most scenarios have zero impact; few of them, those with a lot of clcouds and water effects, may slighlty decrease the performances. Also, the Dynamic Lighting add-on may hit the FPS when several cars are on the track.

    Is it safe to install?
    100% safe. It does not interfere neither with the vanilla weathers, AssettoByNight or the GoodAndBad weathers.

    How do I uninstall the mod?
    Simply remove the directories/files you copied during the installation.

    Today I've tried hundred of time to get a specific weather but with no luck. Is A4S working?
    Yes it is working; try to change the Season. Anyway, the pseudo-randomiztion algorithm is tied to the current date. With this feature all weathers you will get in a given day are coherent.

    I want the fog/haze, how do I get it?
    Lower the air temp and the wind speed to increase the chance.

    I want a wet track, how do I get it?
    Lower the air temp to increase the chance.

    I find a bit convoluted the setting up of a CHAMPIONSIP.
    A4S in itself fully support the CHAMPIONSHIP mode in a very nice and user friendly way. Unfortunately at the moment the Extended Time Slidebar (time ranging between 0 and 24) is not supported by CM in championship mode. I had no other choice for the Championship mode than splitting the mod in two (night/day).

    I find very hard to drive in some circumstances; tyres never warm up and when it is cold/wet/night they cool down. Your mod does not work!
    It works and it works fine. I do not change the grip level of the track (for the moment) and I do not change the physics model. All I do is adapting the track temperature to the actual weather conditions, and from the tests perfromed the track temperature is always pretty credible. My recommendation is to chose carefully the compound, tyre pressure and also the AI level (do not pretend to drive to the limits on the Nordschleife at midnight, in a wet and cold winter night as you would do in a hot and dry Summer day).

    You stated that A4S is 100% compatible with any mod but your mod does not work properly when used in conjunction with this other "xyz" mod.
    My mod is 100% compatible with everything; just beware that if you are using some custom PPFilter you may override some A4S lighting settings (the result could be ugly). Also I cannot state that every other mod is compatble with my mod; this means that you may have installed on your system some mod which alters some settings of CM, thus leading to a not ideal behaviour of A4S. I cannot do anything about it, the problem is on the "xyz" mod. It's up to you to decide what to do.

    How are track conditions affected by the weather?
    A4S modifies two key race variables, the road TEMPERATURE and GRIP (TRACK STATE).
    The road temeperature which depends on the following factors:
    - levels of humidity,
    - the amount of clouds,
    - the current season,
    - the altitude of the track,
    - the declination of the sun
    - the air temperature.
    The road grip made of the following subvariables;
    - the INITIAL GRIP of the session
    - the LAPGAIN, e.g. the rate by which the GRIP increases during the session
    - the GRIPTRANSFER, e.g. the amount of GRIP transferred from a session (Practice/Qualify) to the next one (Qualify/Race)
    I'm using a pseudo-Gaussian ditribution for calculating the INITIAL GRIP while for the LAPGAIN I've chosen a function linked to the first derivative of such curve (the higher the GRIP on track the lower the GRIP GAIN).
    For the GRIPTRANSFER before the AC race engine is launnched, A4S "simulates" the race in order to evaluate the GRIP transferred across the race sessions.
    GRIP RANDOMIZAION is set to zero since it makes no sense in A4S, for obvious reasons.
    Overall the following variables are taken in consideration:
    - air/road temperature
    - air humidity
    - wind (in dusty circtuits, windspeed is used, in conjuction with airtemp and humidity, to evaluate the impact of dust/sand on the track grip)
    - track lenght (used in conjunction with the number of cars to evaluate the number of Laps per session)
    - asphalt typology (roadtrack/circuit old/new)
    - track conditions (clean/dusty/sand)
    - Race typology (Weekend/practice....etcetera)
    - Sessions duration
    - Number of cars
    This mod is not a product. Consider it as a gift. I have no interest in "overselling" the features of the A4S so if I mislead you in someway, that was not my intention.
    This mod leverages on the middleware provided by Content Manager; this means that A4S feaures work within the limits set by CM. A4S is in development as well some required feaures provided by CM.
    1) A4S is a weather engine, meaning that each weather is created on the basis of the variables set by the user before the race. But it's not a Dynamic Weather Engine (PCx like); it is not and will never be. Weather conditions during the race are static.
    2) Weather conditions are set before the race and will be the same across all the sessions; this limitation comes from AC and I cannot do anything about it.
    3) A4S cannot be used in online mode.

Recent Reviews

  1. Rhizix
    Version: 4.1
    Really liking it so far, I find the daytime to be a little too "dim" for my tastes though.
    Still, looks nice and adds to the experience.
  2. Usus Gecko
    Usus Gecko
    Version: 4.0.1
    I have no choose for track : auto
    and i cant choose a date
    installed with cm
    and 4seasons is there
  3. coolwhip21
    Version: 3.2
    Thanks for this marvelous edition to AC! Seems like a totally different sim.
  4. ClaudioWRC74
    Version: 3.2
    thank you for your work and all the updates, nice work
  5. Lucio Distilleri
    Lucio Distilleri
    Version: 3.0
    la mod funziona anche su oculus (anche se un po troppo satura x i colori sgargianti dell oculus), non selezionare openvr altrimenti i filtri non vanno
    suggerimenti: questa configurazione crasha
    aggiungere un moltiplicatore saturazione e esposizione, per calibrare il proprio monitor senza modificare decine di parametri nei file lua
  6. nas404
    Version: 3.0
    very impressive
  7. Peter Kerényi
    Peter Kerényi
    Version: 2.2.1
    Excellent. Driving at night with the starts shining... wonderful. Nice weather engine as well that I need to experiment with more. Thank you :)
  8. Bonehead
    Version: 2.2.1
    Thank you very much!
  9. CobraCat
    Version: 2.0
    Stunning, excellent work! Thank you!
  10. jimclark06
    Version: 2.0
    absolutly amazing! this really change the game on a AC +. thank you very much! you did a awesome job!!
    1. fabrizio piedepesante
      Author's Response
      Glad you liked it.
  11. Lucio Distilleri
    Lucio Distilleri
    Version: 2.0
    for vr: -0.2 saturation, +0.2 brightness, -0.2 contrast
    1. fabrizio piedepesante
      Author's Response
      Lucio, I'll reply in English.
      You already downrated the mod 1 month ago because the "filters do not work in VR". At that time I understood the comment/rating because I had not made clear that VR was not supported (actually I had no idea of issues with VR). Anyway, I replied to you stating that "I do not have any means of testing the mod in VR" and I even put a disclaimer (in bold red) in the A4S overview page stating that I have no idea of how the mod will render in VR since it is not tested at all in such setup.
      Now, apparently you are still using this mod. If so, does it make sense to donwrate a mod because it does not work fine in a unsupported setup? I really do not understand it.
      Have you found a way to use it in VR? Fine! Open a thread in the forum and give the other users some useful tip.
      If you want to contribute to a VR version fo A4S you can open a conversation suggesting your settings. In any case you have to wait until I have a VR gear, or someone else develops a similar mod for VR.
  12. Costas.H
    Version: 2.0
    This is one of most beautiful mods i ever seen in AC! It is really works with dynamic lightening mod and you can run easily thought the night! The visuals are also great! Congratulations guys! Many thanks for this!
  13. themission2
    Version: 2.0
  14. Tzenamo
    Version: 2.0
    Is there any bug where tyre smoke isnt generated? It doesn't show any tyre's smoke with this mod.
    1. fabrizio piedepesante
      Author's Response
      It isn't really a bug, it is a temporary "dessign" choice. At this moment I use "smoke" effects for water effects. The problem is that FOR NOW I have to chosee one or the other, and since I'm investigating some issues (stuttering) with water effects, I chose the water over smoke for testing purposes. In the next release there will be two options: SMOKE_BUT_NO_WATER_EFFECTS and WATEREFFECTS_BUT_NO_SMOKE. In the future the options could be SMOKE_BUT_NO_WATER_EFFECTS WATEREFFECTS_AND_SMOKE.
      At the moment if you want to have back SMOKE (and get rid of water effects, performances will benefit as well) thre is a very easy way: go in each folder of the mod and remove the following files:
      - tyre_smoke.ini
      - tyre_smoke.lua
  15. esteady1
    Version: 1.0.1
    These visuals are unbelievable. Thank you for your efforts.

    Do you have a donation link?

    (You have already earned a donation, I will donate generously again if performance can be improved)

    Thank you!
    1. fabrizio piedepesante
      Author's Response
      Thank you, glad you liked it.
      No there isn't any donation link, I do not need your money.
      Save for AC Competizione ;-).
      Tomorrow I'll upload a new release, a significant step forward.
      It will bring Improvements in visuals in some specific scenarios along with something much more important...
  16. JJ72
    Version: 1.0.1
    I can hardly believe it is the same game at all
    1. fabrizio piedepesante
      Author's Response
      Thank you. Wait for next release, some interesting news is coming
  17. kelnor34
    Version: 1.0.1
    Really great job! Thx so much ;)
  18. englishpointer
    Version: 1.0
    Great mod, thanks for making it!
  19. francescods1976
    Version: 0.9.4
    Sembra perfetto ma come faccio a cambiare l’ora? La barra rimane su 8/18 anche se imposto una delle 4 stagioni... come faccio ad es a correre a mezzanotte o altro orario ??
    1. fabrizio piedepesante
      Author's Response
      Prima di tutto devi avere l'edizione completa di Content Manager (se la barra del tempo è fissa a 8/18 nel menu di gara allora credo tu abbia quella gratuita senza l'"extended time slidebar"). Se invece hai l'edizione completa ed il tuo problema è relativo ai campionati personalizzati, allora devi attendere perché CM ancora non supporta lo 0-24 nei campionati (vedi anche le FAQ).
  20. Nclsbrn89
    Version: 0.9.4
    nice job
    really immersive !!
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