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   Home      iRacing-Help      Dynamic-Tracks
iRacing Dynamic Tracks
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• DYNAMIC TRACK update 2016s4
From 2016 Season 4 release notes
  • Some extensive updates to the Dynamic Track System have also been added that should increase the realism of heat
    mapping and make rubber have a bit more of an impact on your race.
  • Your experience at night tracks has been improved with the new Dynamic Night Shadow Maps system,
    and every vehicle windshield has been improved with realistic reflections.
  • A new character model has taken the driver's seat and is also positioned in the pits,
    and you should start to see wind-animated flags appearing at race courses.  
  • Increased the effective starting usage level, which controls the amount of rubber on the track, for sessions that have a short Practice and an attached Qualifying prior to a Race.
  • Improved the calculations used to conduct heat from the tire into the track, and updated the conduction and convection model for the track surface. This results in lower starting track temperatures, but a significantly more dynamic range when cars interact with the track. 
  • The tearing of rubber from the tires versus from the track has been adjusted so that when a tire is not sliding, it is more inclined to pick up track rubber. Also, the calculations for determining the thickness of the track rubber under the contact patch and the rate at which the track will accept rubber have each been improved. The combination of these changes will make the track rubber build up about three times as fast, and in general be more dynamic.
  • The Dynamic Track system now assumes there is some residual starting dust on the track even before any simulated running of cars or cleaning for a session is performed. The amount of starting dust is related to how must dirt and gravel is around that track, such that a track like Mazda Raceway Laguna Seca is more prone to being dusty than a track like Talladega Superspeedway.
  • Dust will now be picked up and thrown due to air displacement near moving vehicles.
• DYNAMIC TRACK update 2016s3
From 2016 s3 patch 1 release notes
- For sessions using an Automatically Generated track state, the default starting usage will now vary by a percentage based on the following:
- - Session Type = Such that earlier sessions, such as Practice, are cleaner than later sessions, such as Qualifying. This behavior was originally done and this behavior continues with this update.
- - Time of Day = Such that sessions earlier in the day are cleaner than session later in the day, reflecting usual track usage throughout a given day.
- - Weather = Such that the cloud cover affects the likelihood that relatively recent rain may have compromised track time and/or washed away some percentage of the previous track state. Also, for sessions with Realistic Weather, a random factor is also used to account for variation in track usage due to miscellaneous events prior to the session.

From 2016 s3 release notes
We have performed an extensive update to all track surfaces to better model physics collisions, even with tiny particles like sparks, gravel, and marbles.
The dynamic track surface now includes dust and gravel, which is brought onto the racing surface from off-track excursions and affects tire grip.

- Dust and gravel can now be dragged and thrown onto the track by wayward cars, which then interacts with the tires to affect grip and accumulation of debris on the tires.

- The way the Dynamic Track is stored in a replay has been improved to allow sudden changes in the track surface state to be seen immediately.
• DYNAMIC TRACK update 2016s2
- Marble creation rate has been roughly doubled.
- Fixed an issue where marbles were getting cleared from oval tracks during cautions even when the "Automatically clean marbles" option was disabled.
• DYNAMIC TRACK update 2016s1
Source: iRacing release notes.
  • Marbles on the track are now immediately influenced by both the player car and opponent cars to better simulate the effect of following a car closely through debris.
  • Debris will collect on tires of the player car and then be flung off when appropriate. This means tires will continue to emit grass, gravel, dirt and marbles even after leaving the associated surface.
  • The in-Sim Info tab now displays actual average race-line temperature at the start of the session as the track temperature, to simulate a crew member taking some sample measurements with a temperature gun pointed at the track a few minutes before the session begins.
  • Improved the way the server broadcasts the track state by allowing it to adjust what it sends depending upon the current situation on a per-client basis.
  • Improved performance when the dynamic track is not being rendered by removing some unnecessary code.

Renderer.ini tweak post by Dave G (18 Dec 2015):
Track surface decals are the static visuals that sit on top of the track surface itself.
These are things like the graffiti on Nurburgring, or most start/finish lines, static skid marks or discoloration on the track. The dynamic skid marks are controlled by another system.

MaxTrackDecalsInCockpit - This controls the maximum number of primitives (triangles) that will be rendered for decals while driving. A single decal is typically made up of a fair number of triangles so changing this number by small amounts is not really going to show very different results. Lower values mean more culling and better the framerate, but the fewer decals you will see.

MaxTrackDecalsInMirrors - This is similar to the cockpit value and is the number of primitives for decals drawn in mirrors. One thing to keep in mind is that decals only show up in mirrors with the “Higher Detail Mirrors” setting, so if that isn't set this value will have no effect.
• DYNAMIC TRACKS deployed 2015s4
  • Re frame rates Post (Shawn N 10.09.15):
    "Enabling dynamic track rendering can cost 10% to 18% FPS generally.
    Also setting particle detail to HIGH may cost 5% or so.
    Would be interesting to know if setting particles to MED helps, or if turning off dynamic track rend"

  • renderer.ini tweak Post (Dave G 10.09.15)
    In renderer.ini file SeparateDynamicTrackPass
    If you have dynamic track rendering enabled you can try a renderer.ini tweak:
    SeparateDynamicTrackPass=0 ; 0=dyn track renders in base pass 1=dyn track renders using 2nd pass
    Changing that to 1 will enable an alternate rendering method for the rubber/marbles.
    iRacing had mixed results with it internally, on some systems/tracks it helped out quite a bit.

  • Watch Parker Kligerman use iRacing's Dynamic Track system to show how the track's temperature changes over time! clip / storyforum thread.

  • iRacing member Chad D's youtube clip discussing Dynamic Tracks. Thread.

  • Post by Dave G:
    "Particle settings have no impact on rendering marbles.
    Render Dynamic Track Data controls if the marbles will be rendered (note this check box is disabled if you don't have Advanced Shaders enabled)."

  • Bug resolved 8 Oct 2015 - release note.
    "Dynamic Track - Fixed a bug where a session could accidentally initialize the dynamic track with incorrect temperature information resulting in faster laptimes."
    Follow up explanation posted by iRacing staff Daniel G.

    I feel it might be a good time to push the "reset" button in a way, and post some explanation.

    The dynamic track system does have a fair number of "moving pieces" and so it is sometimes difficult to ascertain where things are going wrong. As often is the case though, once you pinpoint the problem it isn't hard to see why it is malfunctioning, how to fix it, and what sort of similar problems you should look for in case the assumptions or mistakes that led to the first bug have contributed to other, yet to be uncovered, issues.

    The last couple of bug fixes to the DTS have fallen firmly into that category. They were puzzling at first until the root cause was identified, and then in both cases it was a total "duh" moment.   

    The fix that went out today (YAY!*) was not related to night mode exactly -- it wasn't that the server had a night mode flag set and clients did not or anything like that. It was a set of conditions which would lead the server to believe the sun was effectively down for the "event" where "event" is a practice, race, time trial, hosted session, etc. with any number of sessions. The vector that represents the direction of the sun was zeroed out between running events, but was sometimes left that way when the server starting calculating track temperatures if the conditions were right and the timing was just so. Those moving pieces.

    As a result of the bad sun information, the server would broadcast a cool track for the entire event. The problem could recur or not, in the next event the server ran, pretty much at random; it would depend on the state of things when it shut down the dynamic track system as part of preparing to wait for the next event to run. This makes perfect sense with what was generally reported and observed: sometimes an entire event would be blessed with amazing grip for everyone there. I'm confident that has been addressed.

    I'm probably not going to go into more detail that this, but my hope is that this reduces rather than fuels speculation as to how this stuff works and where it might go wrong. Hopefully I'm proven right.   

    Thanks for your patience and continued support, and thanks to those who contributed useful information to help round up these issues with the DTM. I am personally very sorry that the first part of this racing season has been affected by these glitches. Some growing pains were to be expected I suppose with the introduction of what we think is a pretty awesome, significant, and complex feature. I think the worst is definitely behind us, but if there should be another major issue we will work as hard as ever to get to the bottom of it.

    * It's pretty impressive to me that I found the root cause of the bug less than 24 hours ago, and the fix is already out to you guys. That is some quick turnaround by the team!

    Q: Why super-grip
    In a word, shadows. This scenario seems less likely, but I can see where the jump-start of the track temperature calculations could occur with the right sun position but not the complete shadow information.

  • Dynamic tracks in development: iRacing video and thread.
  • Let's talk about hot rubber article by Steve Myers (2 Sept 2015).
      From Steve's article:
  • When a session loads, the racing groove you see on the track is actually virtual rubber that is on the racing surface.
    Depending on how the session was setup, you can have a “green” track or one that is fully rubbered-in (or something in-between) and it WILL affect the grip on the track.

    As a session progresses the location of every car on the track is tracked and communicated back to the race server which then aggregates all of that data into cells laid-out on the racing surface and sends it back to each driver in the session. Not only is the rubber from the tires being put into the track, the rubber is being torn or rolled into marbles that are strewn onto the track based on actual “big boy math” (that’s a highly technical term I picked-up from spending time with Dave Kaemmer).

    There is nothing “canned” about this process. It is all being dynamically generated by the actual actions of the drivers, cars and tires in the session. The marbles on the track will also affect the grip your tires have with the road surface. If you want to try running a different line on the track it will take a little bit of work to clean the marbles from that line; and you are going to notice your car is losing traction when you do.

    We have even gone as far as modeling the albedo effect (not to be confused with the libido effect) which influences how much heat will go into the track surface by the position of the sun and the actual “darkness” of the pavement. A light colored concrete, for example, will reflect more energy than a very dark pavement, and the shadowed areas of the track will now be cooler than those sections in the direct sunlight. Ever wonder what it meant when you heard a driver say they “caught a cloud” during qualifying? Now you know

    Read Steve's article for the full story.

      From 2015s4 release notes:
  • The track surface is now dynamic, and models the changes in track rubber, marbles, and temperature. Track rubber is built up under the tires in rough proportion to how hard they are working. Tires generate marbles, and these can accumulate on tires and be thrown off and redistributed on the track. Temperature is variable across the track and is influenced by weather, the position of the sun in the sky, the surface angle of the track, albedo (color), track rubber, shadows, and interaction with cars.

    These variable aspects of the track affect the level and characteristics of tire grip available, and the wear rate. Generally, a rubbered-in but cool track free of marbles will offer the most grip.

    Initial track conditions can be specified for testing and private hosting sessions. The amount of running activity on the track prior to the session can be specified as a percentage, or left to be determined automatically based on the session type. The percent usage amount determines the level of track rubber and marbles at session start. In a multi-session event, each session can be specified individually to simulate changes to the track between sessions due to additional running or from an overnight rain, or a session may be designated to follow immediately and inherit the track state from the previous session. Marbles can be cleaned off the racing surface prior to the session, and also during yellow flags on ovals, or they can be left undisturbed.
Post(s) attributed to a staff member Sept 2015:

Now that the cat-hearder blog has confirmed dynamic track is coming out this build, and we have a race just after the build, I thought it appropriate to open a discussion on the settings to use.

First, not that you would want to, it cannot be turned off.

The main setting is how "rubbered-in" the track is at the start of a session. This is from 0 to 100% with 0 being a completely clean track. Low numbers do not produce marbles until the track builds up a lot more rubber. High numbers start producing them sooner. I think around 60% is the turning point. This setting can be specified for each session or just for the first and carry over.

The other setting is whether or not to clean off the marbles between sessions.

Realistically I don't think road courses ever lose much of the rubber so my opinion would be to start with a relatively high number, let it carry over, and clean between sessions.

Yes, the track does cool some between sessions and keeps the rubber if allowed to carry over.

It takes a very long time to accumulate rubber. How it was explained to the testers is that the tires only have a thin band of rubber. When we change them, only a small amount of that has been worn off and that was spread though all of the corners. Also consider how narrow the tires are and cars running over different lines in the corner. It takes a lot of cars a lot of laps to do much. But the truth is the testers haven't run more than about 30 laps in a single session (on an oval) so we're really not sure just how long it will take to make a noticeable difference. With a single car I doubt anyone has the bladder endurance to find out.

Edit: I should say a big difference since you can see the track changing color with relatively few laps. But what that represents interms of % we don't know, nor how long to go from something like 40% to enough to produce marbles.

Also, drivers will need to be wary of restarts if there are marbles in the corners. Roll through them on hot tires and the marbles accumulate on them (possibly too many at the moment) making them very slick. In limited testing just driving off-line in the corner (say to be nice and let someone through) can cause you problems for several corners.

There is no "random" though there is flag to generate the setting which seems to always put it at 20%.

0 would seem unrealistic since that only occurs when a track is repaved. The dark lines you see at real tracks are from the rubber ground into the surface so there is always some there. The question would be how much and how long into a session before seeing marbles develop.

Our RL drivers might have a better sense for this.
Daniel G (iRacing staff) post (10.09.15):

What Luiz described is in fact what I would expect!

I was just at a Monza hosted session. Low usage track at start, pretty slippery. 40 cars on track, no marbles that I could see in 1 hour.
After 3 hours of session, a few of them could be seen in the 2nd chicane. But only if you pause the replay and look closely, no way of seeing them at speed.
The rubbering seems visible though, and the track got really sticky.
But yeah. It seems to have taken a long time and quite a bit of track usage. Which... seems about right.

There are a couple of relationships going on that will hopefully help explain why something may not meet one's first expectations with regards to track rubber and marbles. First, track rubber...


The rate at which the track will accept rubber from the tires is inversely related to the amount of rubber already there.

Say what? Simply put... a clean track will increase in rubber more quickly than a track that already has rubber. The rate at which rubber will be added tapers off and eventually reaches zero when the track is effectively saturated with usable rubber (at least it helps to think of it this way).


The rate at which marbles are created is directly related to the amount of rubber on the track.

Meaning, a clean track is going to produce very, very few marbles, but if there is a lot of track rubber, marbles will be produced at a healthy rate.


Think of your tire as losing rubber as it goes, much more so when it is working hard. On a green track that rubber will help rubber in the track; on a track already pretty full of rubber, most of it will go towards marble production instead. On a track with moderate usage, some goes towards rubbering in the track, some goes towards marbles, it all depends!

This is why if you play with usage percentages in testing, you'll see that going from 0% to 50% mostly puts down track rubber, but 50% to 100% might widen the groove more than it darkens the heavily-used parts, but the marbles (if left on track) really start showing up!
Dave G (iRacing staff) post (11.09.15):
Soft particles allow for a smoother transition when a particle intersects geometry.
It is probably most notable if you burn out and generate a lot of tire smoke.
Without soft particles you will see a distinct line where the smoke intersects the track and car.

Dave G post:
The only difference at the moment is High Detail enables soft particles.
Going forward this setting will control more aspects of the particle system.

Dave G post:
The other thing to try is turning Particle quality down to Medium Detail.
At High it enables "soft particles" which requires a bit more rendering.

Dave G post (17.09.15):
Why marbles in front of car look ok, otherwise not:
This is your "Anisotropic Filtering" graphics setting. The marbles are particularly sensitive to it. Setting that value higher will give better looking marbles in the distance at the cost of some performance (depending on your hardware). Particle settings don't change the on track marble visuals.
Daniel G (iRacing staff) post (9.10.15):
The usage slider controls the amount of prior activity, but no heat from those simulated sessions are put into the track. It determines the amount of rubber and marbles. The other factors such as angle of the sun, how well the track is surface is facing the sun, clouds, temperature characteristics of the surface, and shadows determine the temperature at a particular spot on the track. But a track with more rubber will be darker, so yes the racing line will be a bit warmer as a result of solar energy.

You could argue for a second slider perhaps, "Time since [end of] prior session" that would potentially leave some heat from prior running.

But to address the topic of the OP (Does track starting state effect lap times and grip?): it should be clear there are many variables involved here. If you put the sun up high in the sky with no clouds on a concrete track, a bunch of rubber is going to probably hurt lap times compared to a clean track. If you put the sun low and make it overcast on dark asphalt, more rubber should improve lap times. Until you are on a short track with 43 cars all running the same line for 40 laps

another Post:
Currently there is no elevation factor but I could add one, that seems reasonable... and perhaps counter it with an air-quality factor per track as well, if that data is available.  There's almost no end to the level of detail in which you can model something, just ask DK about tires sometime. 
I'd like to organise this information better.
If anyone has time to help, it would be appreciated.
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