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Featured iRacing: A Closer Look at the New Dynamic Track Surface Model

Discussion in 'iRacing' started by Paul Jeffrey, Aug 15, 2019 at 20:20.

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  1. Paul Jeffrey

    Paul Jeffrey
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    iRacing Track Surface Update.jpg
    iRacing have recently revealed interesting new information about the upcoming dynamic track surface model set to arrive to the sim very soon.


    Having already introduced a basic first pass at dynamic surface modelling to the simulation, aimed mostly at adding layers of realism for the recent move towards simulating loose surface dirt series racing, iRacing Senior Software Engineer Dan Garrison has shared some interesting insights into what the new tyre surface model is expected deliver to fans of the title:

    "The initial implementation of the dynamic track model featured the server maintaining surface temperatures all over the racetrack, and sending this information to the clients. Temperature from one spot to another would vary according to things like the albedo of the surface, the orientation of the surface with respect to the sun, the intensity of solar radiation as a function of the solar elevation angle, shadows, clouds, and finally from the influence of cars. Areas of inactivity in the shadow would be cool, areas in the sun would be warm, and anywhere cars were dumping heat from engines and tires would warm up further. This gave us a model that would actively respond to many of the real-life factors that one would encounter, and provide a range of conditions to deal with as a race engineer and/or driver.

    When the dynamic track was first released, the weather in the sim was rather static: air temperature and wind might shift a little if the settings allowed such, but the sun did not move and neither did the clouds. This meant that it was possible to calculate the equilibrium temperature of an area on the ground, as it was simply that temperature which created a perfect balance of solar energy being added and the energy lost by conduction and convection. Since the weather was known and the sky was static, if no one was driving on the track the temperatures would remain essentially unchanged save for some small changes that would roughly correspond to changes in the ambient air temperature.

    Once the sun and the clouds started moving, however, one of the major shortcomings of this model became apparent: namely, that the server only kept track of the temperature on the top surface. As a result, as the sun sets or if a cloud comes by, the track temperature cooled rapidly with the incoming solar energy gone. Fluctuation in the rate of heat loss was introduced, as a function of time of year and time of day, to try to account for what would be happening under the surface. However it was a rough approximation of what was really going on, and the overall variation in the cooling rate was kept relatively small in order to avoid strange behavior.

    The new implementation of the dynamic track addresses this by maintaining temperature in multiple layers under the ground, which means that the surface temperature will behave more realistically. With the new model, heat that is stored in the layers below from hours of sunlight will work its way back up and warm the surface. Similarly, built-up heat from cars will last longer if a lot of laps have been driven instead of just a handful. The end result compared to the original model is that temperatures will typically be cooler in the morning and early afternoon, but warmer in the late afternoon. But in general the multi-layer approach will stabilize the temperature on the surface to some degree, in that it will change more slowly in most circumstances.

    Put another way, the layers allow a realistic recording of history that the old model simply could not reflect. Think especially about a hot day that has a hint of a late-afternoon monsoon that is only a very short, mild rain shower: in the old model, the track temperature would have plummeted and stayed cold, even after all the water was gone. With the new model, the heat that was stored in the lower layers beforehand can slowly return to the surface and allow it to regain some of the lost temperature, even if the skies stay cloudy. In fact it was working through this type of scenario that motivated the update to the dynamic track model.

    One of the problems that must to be solved in this approach is the initialization of the temperature in the various layers. If the layers are set up incorrectly, temperature at the surface will drift and fluctuate unrealistically until things eventually settle towards the correct temperatures. To handle this, the server creates a number of samples for each type of material found at the track, and uses an empirical formula to estimate the temperature in each layer that takes into account time of year, the thermal conductivity of the material, and the depth of each sample point where temperature is being tracked. It then goes one step further, and simulates the weather for a few days before the event actually starts, updating the temperature profile of each sample. This ensures that the layers will be at the proper temperatures given the conditions and will behave correctly once the first session starts.

    It then continues to move forward in time and periodically storing additional data points, so that any additional sessions that start after a delay will also begin with appropriate temperatures at all depths. If an event has a two-hour practice scheduled in the morning, qualifying that afternoon and a race the following day, the temperature model will handle that because it has run the weather and modeled the changes already. When a session starts and a piece of the ground needs to know its initial set of temperatures, it finds the data for its material type and the current time, and uses its orientation on the ground to choose and interpolate between a few saved samples.

    This helps address a second shortcoming of the original model that became apparent with the moving sky: at the start of a session, if a fair amount of time had elapsed since the end of the previous one, the server simply looked at the amount of solar energy coming in at that time in order to calculate the starting temperature. If the sun was behind a cloud, it did not attempt to guess at how long or how often it had been behind the cloud, nor did it simulate the conditions leading up to the session. As such, in this case the track would usually start off unrealistically cool, as if the cloud was there all day. In the new model, if the sun was out most of the time leading up to that moment, that will be captured and the track will still be hot but cooling off.

    The new model also features a much better interaction between water and temperature, as the evaporation and removal of heat from that process is calculated more accurately than before. A dirt track in constant shade, perhaps say in Oklahoma, will typically have a track temperature below that of the surrounding air because of the heat lost due to evaporation. Of course the rate of evaporation varies depending upon the temperature of the surface and the air, the humidity, the wind, and the availability of “free” water at the surface. On a chilly, humid, windless day you would expect the track temperature to be close to the air temp, while on a hot, dry, windy day you might expect several degrees of difference between the air and the ground. The upgrade to the dynamic track provides this behavior as a natural consequence of the improved evaporation model.

    Although these changes to the track model are inspired by the anticipation of rain in the sim, hopefully it is clear that the update is beneficial across the board. By modeling heat transfer between the surface and the ground beneath, the reaction of the track temperature due to different events is influenced by what has already occurred. As such, the surface temperature may be relatively persistent or variable depending upon the history that is essentially stored in the layers below. Finally, by running the weather forward during initialization and recording the results, the server is better prepared to handle session transitions that can include large gaps in time and start the track in the appropriate state.

    Link to original article HERE.

    All sounds very exciting, and remarkably detailed... looking forward to giving it a try when it releases in the very near future.

    Stay up to date with the latest news, check out the iRacing sub forum here at RaceDepartment!

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  2. Eckhart von Glan

    Eckhart von Glan

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    you gotta love how they tuck away the juicy bits under layers of technical stuff ...
     
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  3. Marc Collins

    Marc Collins

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    It all sounds very exciting, but is only worth the bother if the tire model and FFB has such high fidelity that a user could detect the small differences in grip that will result from this more dynamic temperature change within individual sections of the track. Honestly, something vastly less sophisticated would be more than enough given the state of the rest of the sim...in my opinion. An overreach, but still nice to have in advance of the rest of the sim catching up to it, as long as it doesn't drain processing resources (server or client) that might be needed for more fundamental calculations that we could actually feel.
     
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  4. Wayne Hutchison

    Wayne Hutchison
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    With a DD wheel you can detect all the subtle differences now - this can only make it better.
     
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  5. Marc Collins

    Marc Collins

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    You can detect the slight difference in grip caused by the modest temperature change resulting from a transition from sunny to shadowed track? Please let us know your equipment, because it's better than what the F1 teams have in their simulators ;)
     
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  6. David Wright

    David Wright

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    From watching some of Jimmy B's iRacing streams (I don't have iRacing myself), the problem with the current system is the temperature changes resulting from a transition from sunny to shadowed track are anything but modest.
     
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  7. Wayne Hutchison

    Wayne Hutchison
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    Yes, I do a lot of oval racing and the feedback is quite clear as the track changes - weather due to rubber buildup, a cloud going over, the sun moving higher or lower in the sky, etc. I use an Accuforce V2 wheel without the SimCommander software and the level of subtlety in the FFB is very good. You don't have to believe it if you don't want to. That's OK with me :)
     
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  8. neuer31

    neuer31

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    Sounds great, when comes finally a good tire model? Never?
     
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  9. F_B

    F_B
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    When was the last time you tried Iracing? With what wheel?
    Sure, it’s not the best in terms of FFB (I prefer Automobilista or AC) etc but it has improved over the last couple of years (member since 2014). So much, that I don't have any issues with how the cars feel. The time of iceracing is long gone imo. I use a Wheelbase 2.5 btw.
     
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  10. Ryan Robbins

    Ryan Robbins
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    I have been on and off of iRacing many times over last 4 years...hundreds of races. It just feels very different than other sims IMHO. I like it a lot, but not as much as AC and ACC. More than PC2 and RRE. Tires feel much better than they used to for me. Still, iRacing requires more careful driving style than other sims IMHO...especially as you progress. Cars sometimes just dont feel as stable as they should to.me? This may be a product of the limitations of an sim racing rig?
    All this said, the way the tracks and tires interact both on dirt and asphalt is very good IMHO, and getting better.
    Imagine if iRacing would overhaul their system with new graphica and tech (which I dont see happening). Would be amazing I think?
     
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  11. F_B

    F_B
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    lol @ the disagrees. :D @BrunoB @Arconian @Littlefysh
    Care to elaborate or is pressing just the button enough?
    Always wonder if it's based on personal experience or just a hate towards Iracing. :coffee:
     
    Last edited: Aug 16, 2019 at 12:43
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  12. DonZmeuheu

    DonZmeuheu

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    Ah this is just a normal day on RaceDepartments Comment Section;) Everybody hates on every sim. Its just ridicolous. About your question....this is just hate on Iracing because when something is as good as Iracing it always have a lot of haters who cant afford it. Its like when People call a Porsche an overpriced VW;) Its not easy but we need to live with these haters and I start to enjoy it. :)
     
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  13. F_B

    F_B
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    Probably, though I'm really interested if these guys have tried it for a proper time (and not just 1-10 hours). I think there's something good in every sim that’s why I have them all (AC, ACC, Rfactor 2, RRE, Automobilista and Iracing). Some of them I use more some of them less, but I'd never talk bulls**t about them just for the sake of it.
     
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  14. Richard Hessels

    Richard Hessels
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    If you spend countless hours behind the same setup you more and more start to understand the most subtle changes.
     
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  15. Marc Collins

    Marc Collins

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    I don't believe you can feel the difference as you pass from shadow to sun. I do believe you can tell the difference between a very hot and less hot track.
     
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  16. BrunoB

    BrunoB

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    This kind of demand to again write a bunch of text of how bad iRacings tire model feels is one of the most idiotic demands I have seen in this forum.
    If you criticize this goofy tire model all fanboys feel obliged to outpour that you are an iRacing hater - and now if you dont want to take peoples time using a lot of text to describe this monstrous TM then you are a hater too.:sneaky:

    I have 5+ years membership somewhat recently in iceRacing and have often expressed how this TMs "binary" behaviour have absolutely no relation to RL car behaviour.
    Of referances I have ealier posted both Thiims and others reviews of this joke - but dont allways feel the need to use time to repeat such "documentation".
    The reason is that in most pseudo religious cults its impossible to get through with some alternative oppinions without being told you are a hater of the cult.

    Beside comparasment of day to day RL driving with iceRacing driving I had some experience from my younger days driving FF1600 - so at least I know a few things of what a racing car absolutely not will do in certain situations.
    And thats the main reason Im not an iceRacing member today.:)

    ByTheWay: Just like iceRacings binary TM is quite goofy then a binary question only opening 2 possible answers is also quite goofy = either: personal experience or just a hate towards Iracing.:roflmao::roflmao::roflmao:
     
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  17. tlsmikey

    tlsmikey

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    I'm an iRacing member for about three years now and there are certainly cars that could use a tire model improvement (Porsche cup is off to me), but the GTE's are excellent and as a whole I like the more subtle approach they've taken.

    I started with a T500 wheel in iRacing and every car felt numb to me with little ffb. I then started using irFFB to enhance the ffb and the T500 was a joy to use. Moving to a DD wheel has only improved things another 10 fold.

    No, it isn't most peoples cup of tea but iRacing has never been for everyone. It's a pretty serious sim and they've gone out of their way to not add any artificial effects so this may not suit some of you.

    In any case, can we all just appreciate the detail they are going to with the dynamic track. Amazing work yet again from these guys.
     
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  18. F_B

    F_B
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    Well, at least that’s an answer. Cheers.

    And I’m certainly not a fanboy as I quite like all of the sims available (listed them before).
    The thing which strikes me is that some people describe their experiences with the tires/TM, ffb, "iceracing" which I just cannot relate to or understand as I'm enjoying many cars in Iracing. And trust me I think I can differentiate between good and bad ffb & car feel. I want to feel subtle nuances and differences when driving and Iracing provides those through my wheel. Nothing to complain about. Sure, Automobilista and AC might be a tad better in that regard imo but I'm fine. So…when I read some of these/your complaints I wonder if I'm doing something different? Or am unable to feel all those complaints? Not simracer enough? :D :coffee:
     
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  19. BrunoB

    BrunoB

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    ;)
     
  20. F_B

    F_B
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    Yeeeez. :roflmao:
    Where have I called you a hater in my last post?
    We’re running in circles here.
     
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