[Bug] Losing vsync in flight

  • Hi again,

    I found another weird issue: My vsync occasionally gets disabled when flying resulting in heavy screen tearing. If I then point the camera straight to the ground and back up again the Vsync comes back until this happens again.

    I'm using Vulkan API and my graphics card is an AMD Radeon RX 6600XT with latest drivers (but this also happened with older drivers in AFS2), my operating system is Windows 11 Pro (also up to date).



  • This is so called adaptive VSync I guess? Is there a chance to get a classic Vsync as another option?

    The situation is that my framerates don't fall below 60 FPS but by the Radeon Software's framecounter when this happens, so I guess there is some kind of minimal lag spike causing this but the VSync does not kick in after the drop is over automatically. When I look down to the ground and back up again it comes back and in the same situation the framerates are reported at stable 60 FPS then. The frame drops are so minimal that I don't notice them and even the frame counter does not report anything, it shows 60 all the time. I also noticed that taking screenshots with the sim's screenshots key (causing a short stutter while saving the screenshot) also kills Vsync consistently every time.

  • Okay, I found switching off the beautiful high quality antialias (which is a shame I have to disable it) helped a bit as it leads to the Vsync loss happening less often but I still think there is something wrong with the Vsync because:

    • My frames don't go below 60 when this happens (I don't notice any stutter nor does the AMD frame counter show anything)
    • The Vsync should come back on it's own after short framedrops or frame time spikes but currently I have to move the camera to the ground and back up again to get it back on
  • I want to bump this a bit because I still have this issue.

    For clarification: I know that reducing settings helps a bit but it does not completely solve the Vsync turning off and NOT nurning on again. I understand that adaptive Vsync is only working if screen refresh rate is achieved but this is the cast in most situations I lose the Vsync.

    In short: The main issue is that the Vsync does not turn on again after a slight stutter (so slight I don't even notice and I'm very sensitive to stutters and low framerates), I always have to point the camera down to the floor and back up again.

    Further, my computer is not exactly on it's limit when the issue occurs, most of the time I get stable 60 fps when it happens, also reported by the Radeon Software frame display.

    To show what's going on I made a video, starting form minute 2:35 you can see what's gong on and this happens again and again in this flight (and this is why I move around the camera very often when this happens and then look down and move again to show the difference).

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  • I made one more video to proof that my performance should not cause the Vsync to disable at all, my framerates are above 60 FPS all the time and most of the time are significantly above 60 FPS. So, even if some higher frametimes here and there might cuase the Vsync to disable, it should come back quickly after that - I still think there's is something wrong here, please have a look into this.

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  • Jet-Pack (IPACS) I think I found a way to solve this: When using windowed display mode instead of fullscreen, limited to 60 fps, I don't need Vsync because there is no tearing. The downside is, I have a window and no fullscreen visuals.

    The solution for this would be a borderless window mode in addition to fullscreen and window modes already available. The borderless window mode would then technically be window mode but look exactly like fullscreen mode, covering all of the screen. The downside is that someone at IPACS has to code a borderless window mode.


  • Someone told me the Vsync should turn off if FPS falls below screen refresh rate and this is what I see in the sim. The only issue is, that it's not coming back when the frames are high again.

    Anyway, even if this is a driver issue, it can be solved by adding a borderless window mode because this would render Vsync obsolete.

  • We don't think it's a bug on our side, rather a driver setting. Making a borderless window has disadvantages compared to a real fullscreen window and might break performance on existing user machines. So before we do a change here, we need to be absolutely sure it doesn't cause other issues.

    We have also tested it on our system with an AMD Radeon RX 6600 XT and the latest AMD driver and we do not observe it here.

    You might want to test with Vulkan and OpenGL and see if that causes an issue.

  • I don't think a borderless fullscreen will cause issues for others if it is optional as in many games these days. There you can simply chose between fullscreen and borderless window mode and use what works better for you.

    With OpenGL the issue does not show up but overall performance is significantly worse then.

  • Ich bin echt begeistert von der Arbeit. :thumbup:  :)

    Würde mich freuen wenn man solche super Arbeit auch über Steam kaufen könnte???

    Gibt es möglichkeiten es bei steam an zubieten :?:

    Vielen Dank .


    Edited 2 times, last by EXTRA300L (August 25, 2022 at 6:10 PM).

  • Wenn du die Szenerie meinst? Da müsstest du admin fragen, ob IPACS das über Steam veröffentlichen wollen. Von meiner Seite steht dem nichts entgegen und Lizenzprobleme gibt es auch keine, theoretisch könnte IPACS die Map also in einen DLC packen und über Steam veröffentlichen.

  • Update on this issue: It's still happening but not that often as half a year ago (maybe because of graphics driver performance improvements, but I can't tell for sure) so I enjoy flying again. I also ordered a freesync monitor to hopefully get rid of this once and for all.