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PC Why is the jitter not fixed yet?

Discussion in 'Assetto Corsa' started by Richard Eriksson, Aug 24, 2015.

  1. Reinstalled AC after a while, being busy with having a new child arrive :)

    Still the annoying jitter in the visuals is present on all PCs i have tried it on (5 different machines).

    Note it is separate from stuttering. It is a constant uneven framerate, look at the scenery in a turn to see it.

    It should be silky smooth at 60fps vsync but drops a frame apperantly constant. This has been discussed on Steam, official forums and elsewhere since EA. Still Kunos dismiss it.

    In 2014 already measurements where made by community members showing all tested machines had it. If 60fps vsync it would always render frame 1-5 in same time then stall and hiccup on frame 6, constantly. Not in replays only when driving.

    This happens on ALL machines where framerate is synced to something not an even multiple of 50 (49.98 according to PMxMon).

    In framerates synced at 50,100,150 etc. it is much less prominent and frametimes are more even.

    We did a new investigation again with the latest version this weekend using 3 different machines with powerful HW. All exhibited the issue.

    Process, thread and render monitors where installed (PMon, Sentec) and indeed, it still stalls on a frame at the same interval ALL the time during rendering. Hence the jitter.

    Moving to a TV display at 100hz and syncing mostly fixes the erratic frame times and it is way smoother as does vsyncing at 50hz on HDMI.

    Many people diregard seeing these jitters, but to me they ruin the entire experience. Still can not use the software as it looks like crap.

    Our findings is that the stall on every 6th frame is longer with AI as well. As evidenced before by others in 2014 and 2015.

    So for me and my pals still no AC.

    Kunos, fix this issue or at least admit there is a flaw in the render/physics engine sync. It has been reported by thousands now so it is time to squash it.

    And IF you claim it is not on your machines, believe me, it is... But you may be able to see past it. Look at the trees... Or measure frametimes.

    And this is separate from any stuttering as this is a constant desync that breaks the entire fluidity in the rendering.
    • Agree Agree x 4
  2. They won't fix it because the majority of users don't even notice it.

    I'm surprised though that people unable to drive with the jitter can tolerate the lag that comes with vsync. High framerate, with a bit of tearing and no lag is the way to drive.

    I want the latest information available on my screen, right away, at all times.
    • Agree Agree x 2
    • Like Like x 1
  3. I'm surprised people into sims will want to break immersion with non fluid motion and tearing artifacts :)

    To me any non fluidity is a huge immersion breaker. And with NVidia adaptive vsync and maximum prerendered frames set to 1 (push to render as soon as possible) input lag is very low...

    Borrom line is i use sims to be immersed (hence simulation) not to optimize to compete. It's like the guys you used to know turning off all the fance graphics in Quake3 back in the day, to aim better. Competitive, but not as immersive...

    For really fast screens however, like say 144hz. sweeps it is good to turn it off.

    As for not fixing it, well it is an annoyance for people not seeing it as well, or potentially so, as it would indicate further desync in the rendering pipeline. This could give rise to all kinds of physics/visuals hiccups, like cars moving erratically and such.

    There are also some huge CPU overhead still, and hivvups with the AI. So it's not exactly "smooth" overall.

    So i really think a deep dive into the engine code again could be a good idea anyhow.

    While they're at it, they could rewrite that shoddy deferred renderer, that produces jagged artifacts on all light refelctors :)
  4. Cote Dazur

    Cote Dazur
    AC Addict

    Over 1200 hours on an old PC connected to a 32 inch 60 hz TV and I have no idea of what you are talking about! I will not look for it either and intend on enjoying my next 1200 hours.
    • Haha Haha x 3
    • Like Like x 2
    • Agree Agree x 1
  5. Richard is there any thread in AC forums about this? It can help the devs better by having a thread to discuss there, or at least for them to see even if not replying back.
  6. Tobbe Bergman

    Tobbe Bergman
    @ Simberia @Simberia

    In sharp turns I always felt that AC was really choppy if that's what you mean by jitter !

    What's even worse IMHO is the thin lines across the track @ Eau Rouge and Nordschleife :(

    And what about the popup textures @ the end of the long straight @ Nordschleife :(

    Those issues don't belong in a next gen Sim IMHO :confused:
    • Agree Agree x 3
  7. Well there has been threads on it in the past. Big reports where filed but then closed with no action by staff. Discussion and data gathering on the issue has been going on since 2014 by users... Steam forums have plenty on it too. They know of the issue...

    My guess is they also know the exact cause, as they also know the cause of the physics desyncs of the AI and CPU overhead. The problem is it would be hard to fix as my further guess is that it is artifacts of the way the sim engine is designed...

    @Mikaela Andersson , exactly that choppiness is what we are talking about here... It is indeed most noticable in sharp turns, as sideways motion causes you to see clearly at the scenery that there is a jitter or desync. It is smooth as in it is always producing the same frametimes more or less, but at exact intervals there is one or two frames stalling out causing a very short "stop" in the panning around, hence the choppy motion.

    Texture pop in i dont have that badly... I have jagged lines on reflectors as a result of the deferred render being odd (look at chrome details in sunshine... They look very fuzzy).

    The reason why i am going to raise these things all the time? Well, the sim had a really good foundation that can make it really good, but it is technically impaired. And that is a shame...

    And i do not see progress in the engine department, only news of nee cars and tracks. I was really hoping for some of the really crippling stuff to be gone by now and IF it's not i am gonna go on about it... Because it annoys me ;)
    Last edited: Aug 25, 2015
    • Agree Agree x 1
  8. I've had no issues with AC stuttering since I've been playing either.

    1920x1080 @ 120hz, i5 3570k 4.3GHz, 16GB DDR3 RAM @ 2400MHz and an MSI 980.

    Only place I notice drops sometimes is in Foxhole on The Ring.
  9. Bram

    Roaring Pipes Maniacs | #27 Staff Premium Member

    Pretty sure they read it here as well.
  10. Note that this is not framerate drops or stutters. It is a constant loss of frames, at an exact iterval giving animation that is less fluid. I have no framedrops either and render solid 60fps at all times. That is not the problem here. Problem is with a recurring delay in the render loop (every 6th frame or so)
    • Agree Agree x 1
  11. I ran for a little while at 50Hz with vsync and rendered frames set to reduce input lag. In the end I was more happy with more framerates and tearing. Competitiveness is a factor for me.

    I do understand how upsetting the jitter can be for some, I'm just not that sensitive to it. You probably already tried running your screens at 50Hz?
  12. Tobbe Bergman

    Tobbe Bergman
    @ Simberia @Simberia

    But why is it only occurring on sharp turns ?
    The gameplay is otherwise butter smooth on my system !
  13. On sharp turns? Depends if more cars get close together in such moments and you get some fps oscillations. Does it also happen with 1 car on track and low-medium settings?

    I personally use vsync off and frame limiter of 64. I heard 83 also works good. Put audio latency to normal in the Audio menu. And I also use fullscreen mode, and when I minimize the game and return, I press alt+enter to activate it again.

    Could you post a video of those situations and show on screen the render stats app:
  14. Tobbe Bergman

    Tobbe Bergman
    @ Simberia @Simberia

    Only on sharp turns like the first @ Spa !
    Only one car.
    Video settings doesn't seem to matter ( MSI GTX980 + i7-4790K )

    tried changing the latency ( smallest setting used ) yet !

    I tried making a video but it did not look the same as the real gameplay.
  15. Show using the render stats app.

    But first you could try just driving by yourself and disable fmod to see if a part is related to it. Open audio.ini and put ENABLE_AUDIO=0 in C:\Program Files (x86)\Steam\steamapps\common\assettocorsa\system\cfg
  16. Matheus Machado

    Matheus Machado
    #17 Talking Door Racing Staff Premium Member

    Despite having a good hardware, graphics settings DOES matter. If you use some overlapping features you become prone to having stutters and bad rendering. The most commonly found mistake is using both AA and FXAA at same time.
  17. Once again, this issue is unrelated to stuttering or bad framerate. For instance, in monitoring my framerate reads as constant 60fps. solid with only 60-70% GPU utilization even with 25 AI.

    But the frametimes read uneven, for every 5th or 6th frame ALL the time. Constantly. Regardless of if the gpu load is 40% or 80%.

    Please dont mix this up with framerate stutters and low framerate.

    For the third time, it's unrelated to hardware, framerates, settings... It's a constant frametime jitter caused by a bug.
    • Agree Agree x 1
  18. For an application such as AC that uses deferred rendering you SHOULD use FXAA (after pass render) and MSAA (pass render) at the same time... Deferred rendering is a multistep render process, where MSAA affects the first initial pass and FXAA or similiar is the only way to apply AA to the following passes (where most of the effects are applied).

    Thus you SHOULD have both activated in AC to avoid both regular render jaggies (line aliasing) and post process artifacts (shader aliasing).

    So no, that is not a good recommendation at all.
  19. Lots of interesting techno stuff. Would be more beneficial to post this on official AC forum, unless OP has some reason not to (like being banned there).
    I have tried all different permutations of Sync and frame caps, and the only thing that works for me is a combination of
    - VSync (adaptive, prerendered frames set to 1) and
    - Frame cap slightly higher than monitor refresh rate (I use 61 on 60Hz display)

    EDIT: BTW, FXAA looks like crap in AC, surprised anyone would want to use it if machine can handle MSAA
  20. Note my point above on MSAA and FXAA. They are for different things in an engine like ACs. MSAA only will not give you AA for shaders or lightmaps as they are postprocessed by the deferred renderer. So to get AA on the full scene graph you need both activated.

    ACs afterpass renderer is a bit shoddy however and still gives some artifacting on surfaces with reflection for instance... And the DoF effect has a lot of artifacting.