Why is the jitter not fixed yet?

[Richard Eriksson]

Ran it through PIX Remote and the DX dev tools again last night. It is now clear to me that there is a huge delay in the timing loop.

The render calls come at even intervals. But every 1/6th or sometimed 2/6th frame is always delayed. This means that some logic is probably in the loop set to trigger at this interval. It is not fast enough to complete in time for the render call to be in sync.

As for what it is, dunno... You would need source code and PIX symbols to profile it better to find out and only Kunos can do that.

It's been noted as an issue in the past but dismissed and closed every time by Kunos.

So i am not holding my breath for that to happen...

It's a VERY good sim that is flawed by bad tech really...

Because as we know the jitter is not the only problems. It annoys ME the most but many people have other issues still with the core tech ,like the insane CPU stalling for some AI situations... Or the performance hit on AMD using DoF.

As i wrote earlier i was hoping to find fixes to the core rather than excessive content like more Italian hatchback road cars...

 

[Nathaniel Dwayne Hale]

I am so happy you made this post! I always saw stuttering, and I always thought that it wasn't true 60FPS, even if fraps said it was. I am sooo glad that I found out I wasn't being silly, and indeed saw true fps reduction. It was so weird that my FPS counters showed steady 60+, but my eyes saw 30-40. A lot of the time. This was a huge issue to me, and I've thought of using a camera to record at 60fps and see the actual frames, I've just never gotten around to it.

Seeing these fps drops is horrible! I just hope that the physics engine isn't effected by this. :S

Have you found out how to alleviate that even by a tiny bit?

 

[Richard Eriksson]

I am so happy you made this post! I always saw stuttering, and I always thought that it wasn't true 60FPS, even if fraps said it was. I am sooo glad that I found out I wasn't being silly, and indeed saw true fps reduction. It was so weird that my FPS counters showed steady 60+, but my eyes saw 30-40. A lot of the time. This was a huge issue to me, and I've thought of using a camera to record at 60fps and see the actual frames, I've just never gotten around to it.

Seeing these fps drops is horrible! I just hope that the physics engine isn't effected by this. :S

Have you found out how to alleviate that even by a tiny bit?

If the delay is caused by some physics update then it could delay physics. More likely is that it is a desync of physics (movement) and render (visuals) mening that they can not manage to update in sync. This appears to get worse with AI (CPU loads)...

But as i said, it should be profiled from source code by the devs to find the bottlenecks.

One way to slightly alleviate it is to run in 50hz vsync provided your screen can do it. It brings the off-time frames a bit closer to actual render buffer flips. But not entirely good... It is still evident.

It is possible that the delay is caused by some particular thing in the engine and that perhaps some option could alleviate (sound for instance) but i have yet to find it. Without proper dev support on profiling it is hard to say...

IF the devs should happen to read, my suggestion as a fellow software engineer with years of sim experience in the military fields is this: Profile every call in the render loop. Look for the calls happening from render outwards to physics or control if any and time them.

Set a break when a spin in the render loop took longer than target frame time delta (16,6667 ms @ 60fps) and examine the stack to see what was called on those occations.

 

[Matheus Machado]

That recommendation I wrote above came from the debs. Haven't had the experience myself, as I run the game on the bare minimum settings averaging 35FPS under normal load.
I used to get these stutters at nordschleife specially under bad servers. And it is always related only to the Gpu. Now I almost never get these stutters again. (After 1.2)

 

[Richard Eriksson]

That recommendation I wrote above came from the debs. Haven't had the experience myself, as I run the game on the bare minimum settings averaging 35FPS under normal load.
I used to get these stutters at nordschleife specially under bad servers. And it is always related only to the Gpu. Now I almost never get these stutters again. (After 1.2)

Well it holds true IF you have regular GPU load issues, like low framerates as both at the same time induces a high penalty on the rendering.

The issue we are discussing here however is evident mostly to people that run the sim at 60fps+ vsynced without any other performance drops.

At unsynced 35 fps there would be so much other jitter and framedrops you would not notice this at all...

 

[Radu Oros]

I am so happy you made this post! I always saw stuttering, and I always thought that it wasn't true 60FPS, even if fraps said it was. I am sooo glad that I found out I wasn't being silly, and indeed saw true fps reduction. It was so weird that my FPS counters showed steady 60+, but my eyes saw 30-40. A lot of the time. This was a huge issue to me, and I've thought of using a camera to record at 60fps and see the actual frames, I've just never gotten around to it.

Seeing these fps drops is horrible! I just hope that the physics engine isn't effected by this. :S

Have you found out how to alleviate that even by a tiny bit?

Are you using the correct resolution and frequency refresh hz in desktop and in game, and then the correct frame limiter?
For example when I play CS:GO I have a high resolution on my desktop with 60hz, then on the game I use a low resolution (1024*768@75hz), because my high monitor resolution only does 60hz. And then on the game I need to use fps at least higher than the refresh, so I use 83 (actually I need to put 84 because cs:go has a difference of ~1 fps, so with 84 I get 83). But if I put fps limiter below 75 using 75hz frequency, then the game looks very choppy.

So just make sure your resolution in the game and the frame limiter used (with vsync off) are good, so put the fps higher, like 64 or 83 for 60hz, and 83 for 75hz, and higher if you have a higher refresh hz.
Also don't use 3rd party apps, those can be heavy for the pc performance and will take you fps and give you choppy gameplay, so disable them in options-general, and try without apps or just with the native ones.

 

[Tobbe Bergman]

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.

Believe me when I say that I have tried every possible configuration !

 

[Radu Oros]

Believe me when I say that I have tried every possible configuration !

Did you try other pc? Try different monitors if available, and types of pc-monitor cable connection, and try other pcs if you have any in the house.

 

[Tobbe Bergman]

Did you try other pc? Try different monitors if available, and types of pc-monitor cable connection, and try other pcs if you have any in the house.

I should mention that these thin white flickering lines are completely gone when using the cockpit view so it is definitely something on Kunos side that isn't optimized.

I made a vid of the issue but when I put it on Youtube these fine details hardly shows at all !

I have put it on a server here to see:

www.studiobergman.com/thin_white_stripes_eau_rouge.avi

It's a large 1.5 GB file but it clearly shows the issue !

 

[Richard Eriksson]

Frametime log from PXm... Framerate on the left, Frametime (time to flip) on the right...

This is at 60fps vsync, ingame or adaptive in NVidia CP doesn't matter.

See the ones with frametimes at 20+? Those are jitters...

 

[PhilS13]

I thought from explanations on steam forums it was due to something in the game running at 50Hz, giving equally spaced jitters in time when trying to display at 60Hz. This is more random than I expected... So running the screen at 50Hz only "hides" the problem by having normal frame time closer to jitter frame time?

 

[Requiem84]

Should really post those details on Kunos' forum.

With these facts you might have a chance they take notice.

 

[Richard Eriksson]

I thought from explanations on steam forums it was due to something in the game running at 50Hz, giving equally spaced jitters in time when trying to display at 60Hz. This is more random than I expected... So running the screen at 50Hz only "hides" the problem by having normal frame time closer to jitter frame time?

Exactly. The problem is still there, but it is not as apperent in 50hz sync because the frame times are longer anyhow...

 

[PhilS13]

Exactly. The problem is still there, but it is not as apperent in 50hz sync because the frame times are longer anyhow...

The software you are using to grab frame time...is it user friendly? Free? I think if you show up on Ac forums with a package and a procedure for normal people to run it on their machine and measure the frametime hiccups it would encourage Kunos to look into it.

 

[Richard Eriksson]

The software you are using to grab frame time...is it user friendly? Free? I think if you show up on Ac forums with a package and a procedure for normal people to run it on their machine and measure the frametime hiccups it would encourage Kunos to look into it.

For the above i was using obscure software from work, that is hooking by a custom driver.

But for regular measurements MSI Afterburner and OSD can be used i think. I recall that in it's monitoring tab in settings you could write a log file to disk with framerate and frametime that is accurate enough to show the problem.

Would be intetesting to see a readout from AMD GPUs as i only have access to NVidia hw...

As for posting on the official forums, i dont have an account. If someone has and wants to link this thread (IF they alloe that) go ahead... But it's been mentioned to them during EA with frametime logs by users but then they closed the bug in the tracker without action... But maybe now they have more time to look.

Or if Kunos could share a bit on how the rendering actually works in AC (without giving away any code or secrets) we might be able to help them find the cause.

 

[PhilS13]

@Richard Eriksson

Do you have some hope with this?

Assetto Corsa 1.3
Physics
64-bit natively supported and car physics calculated on multi-thread. The physics engine has been reworked to become completely multithreaded: as a result, the driving precision is augmented, the accuracy further improved and the physics solver has enough horsepower to completely resolve any difficult calculations any speed, achieving butter smooth Force Feedback and complete elimination of signal noise and vibrations. We'll be back with more details on physics updates when the new build will be released next week.

 

[Richard Eriksson]

@Richard Eriksson

Do you have some hope with this?

Assetto Corsa 1.3
Physics
64-bit natively supported and car physics calculated on multi-thread. The physics engine has been reworked to become completely multithreaded: as a result, the driving precision is augmented, the accuracy further improved and the physics solver has enough horsepower to completely resolve any difficult calculations any speed, achieving butter smooth Force Feedback and complete elimination of signal noise and vibrations. We'll be back with more details on physics updates when the new build will be released next week.

As i wrote in that thread about 1.3, problems are still there. BUT, with 1.3, and an EXTERNAL framerate limiter set @ 60fps AND in-game vsync on, it is MUCH better. Previous builds no matter of fps limiting has helped, but this time it works. Only with external app though, not in-game as that limiter seems to not work at all for me.

Now that 5/6th frame drop seems gone, but there are still variance in frametimes, so small jitter on scenery, but overall it is now much better.

@Mikaela Andersson can you also try if this works for you?

 

[Tobbe Bergman]

As i wrote in that thread about 1.3, problems are still there. BUT, with 1.3, and an EXTERNAL framerate limiter set @ 60fps AND in-game vsync on, it is MUCH better. Previous builds no matter of fps limiting has helped, but this time it works. Only with external app though, not in-game as that limiter seems to not work at all for me.

Now that 5/6th frame drop seems gone, but there are still variance in frametimes, so small jitter on scenery, but overall it is now much better.

@Mikaela Andersson can you also try if this works for you?

Not sure how to limit the framerate ?

 

[Bokonon]

Not sure how to limit the framerate ?

It's in the settings menu, I have mine limited at 90 fps, it works well for me, I used to to have issues at a few of the sharper turns at Spa, but it has worked fine for me for quite a while now, I may try 100 fps to see if I notice a difference. I do not use vsync to avoid lag, but the frame rate limiter renders vsync pointless imo. In games with no inbuilt frame limiter I use MSI Afterburner to limit the framerate. It works very well.

 

[Tobbe Bergman]

It's in the settings menu, I have mine limited at 90 fps, it works well for me, I used to to have issues at a few of the sharper turns at Spa, but it has worked fine for me for quite a while now, I may try 100 fps to see if I notice a difference. I do not use vsync to avoid lag, but the frame rate limiter renders vsync pointless imo. In games with no inbuilt frame limiter I use MSI Afterburner to limit the framerate. It works very well.

I tried using vsync and frame limiter in AC and the one in MSI Afterburner
Everything gave me all sorts of problem like stutter and micro freeze etc etc !

All I want to get rid of now is the build ups ( Like the ones I used to have in games from the PS1 era ) and white lines across the track as they are the definite immersion killers IMO "