Bobsk8

Stutters at low altitudes in P3D version 3.4

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Been flying P3D for almost 2 years now, and never had any real problems, or OOMs or FPS issues with a 3 year old i5 with a GTX 750 Ti card. I started flying a couple of A2A aircraft then the Q400 then the NGX, and A2A Connie, etc. and most of my flying was probably from 6,000 AGL up to FL370.  About 6 weeks ago I got hooked on flying helicopters, and I have 3 Milviz copters which I love, the 530F, the 407 and the Huey Redux. What I started to noticed was occasional stutters, which I had never noticed before in P3D. I will be flying along about 2,000 Ft AGL, and FPS seem about normal, and all of a sudden I get a sharp drop in FPS for a couple of seconds. It is almost like it catches on something and then back to normal.  I Had run my FPS unlocked or unlimited all this time, and this morning I decided to try an experiment after reading a post by VGBaron, and locked the Frames to 20 and then 22.  This seemed   to eliminate many of the stutters I was getting, although I still had a few on about a 65 mile flight. When I get get one of these stutters, the FPS would momentarily drop to as low as single digits, just for a second, and then go back to 22. I am thinking that this must be happening as the sim is loading a new area of scenery. 

Now my question is, has this been happening all along, and I just didn't notice this when flying at much higher altitudes, and incidentally I have made it a habit of not turning on the FPS counter from almost the day one. In other words, is it much more of a load on the sim, when flying at a low altitudes, because you are closer to the scenery and it is moving faster, compared to what you would see at say 7000 feet or higher and that is why I am now noticing it? Anyway, I was surprised to find that the sim looked pretty good with the FPS locked to 20 and then 22. I was always striving to see higher FPS and it usually varied from around 38-over 50  when unlocked, in most areas.  I think I will keep it at 22 for awhile and see what it feels like.

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Hi Bob - 

Several things - yes, when you fly low and slow the system is trying to provide more detail and is working harder, this will be especially noticeable if you are over or near water. The low frame lock frees up your cpu to put more effort into loading etc rather than trying to get high FPS.

If you can find the right balance for your system, you will be amazed at how smooth P3D is at 20-22fps.

One other thing you might look at, fly default fixed wing low and slow and see if you get the same issue - thinking it might be the helicopter models themselves having an effect - probably not but worth a check.

Other thing to check is if any addon or system process is doing a check or loading something.

 

Vic

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3 hours ago, Bobsk8 said:

Now my question is, has this been happening all along

Yes.  This has been my serious beef with P3D.  When flying GA and is still at 2000 FT, do a turn and you will also see the stutters there too.  Most of tube flier never see this because the gain in altitude is so fast.  If you do turns on approach and at low enough altitude you will also see this.

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2 hours ago, vgbaron said:

One other thing you might look at, fly default fixed wing low and slow and see if you get the same issue - thinking it might be the helicopter models themselves having an effect - probably not but worth a check.

I have never fly helicopter and always see this with all of my fixed wing aircraft.  This will happen especially bad with ORBX scenery. To the point that I now got rid of all ORBX stuffs and GA aircrafts in P3D and only use tube liners.  I tried everything, FF, Affinity mask, my FPS would be around 30-40 with RealAir Legacy V2 and then stutters!

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After giving up on TrackIR that needs 30 fps, after using cashplane.

22 fps is the sweet spot for me just a matter of balancing your setting now Bob.

I did a little guild it's below in my sig if you want to have a read?

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22 FPS locked seems to work very well. 

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I think I have hit on something tights as far as the stutters go.  I have been trying to track down a slight stutter issue with P3D version 3.4, and one of the things I did was to monitor CPU usage in Task manager while flying. I noticed tonight that after about 30 minutes or more of flying, I started to get a bit of stuttering and I now have my FPS locked in P3D to 22, and it is capable with the scenery I am flying over of around 40 fps normally . I also saw the FPS dip a bit under 22 to around 18 or so when I would see the micro stutters. I now looked at the CPU usage with Task manager, and I see that AS 16 is using around 25% or more  at times, and the weather was just some occasional cirrus clouds ( Rex soft clouds) and a steady 13 knot breeze. I felt that this percentage of CPU usage was a toohigh, so while flying, I shut down AS16. I then restarted it, and now the CPU usage is around 2-3 % and the stutters are totally gone and FPS are rock solid at 22. I flew for another 20 minutes, and it remained the same. Any ideas why this could be happening? I have the latest version of AS16  6255. 

 

I also posted this on the AS 16 forum. Seems quite a few others having the same exact problem. https://hifisimtech.com/forums/showthread.php?7863-Stutter-appears-and-increases-over-time-in-P3D-V3-4-18-19475&highlight=high+usage

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It is weird that we now think 22fps is acceptable since it is smooth. In reality, we need much higher than that (35+) at low altitude because when the plane is in a tight turn, the terrain needs to rotate smoothly. 22fps cannot achieve that by simple arithmetic unless you mainly fly in a straight line at low altitude.

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2 hours ago, glider1 said:

It is weird that we now think 22fps is acceptable since it is smooth. In reality, we need much higher than that (35+) at low altitude because when the plane is in a tight turn, the terrain needs to rotate smoothly. 22fps cannot achieve that by simple arithmetic unless you mainly fly in a straight line at low altitude.

Sorry but that is completely incorrect. Smoothness is not a function of FPS. If that were the case, those who say they run at 60fps would never have stutters.

*IF* your sim is smooth at 22, it will be smooth no matter what you are doing, flying straight or turning. There are other factors but FPS and turning are not the major players.

If you tune your system for smooth at 22 in the turns it will be fine straight and level. If you set it up for smooth straight and level it is possible you'll get stutters in the turns.

 

Vic

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+1 Vic

P3D is nothing like FSX at 22 FPS.

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20 hours ago, vgbaron said:

Sorry but that is completely incorrect. Smoothness is not a function of FPS. If that were the case, those who say they run at 60fps would never have stutters.

*IF* your sim is smooth at 22, it will be smooth no matter what you are doing, flying straight or turning. There are other factors but FPS and turning are not the major players.

If you tune your system for smooth at 22 in the turns it will be fine straight and level. If you set it up for smooth straight and level it is possible you'll get stutters in the turns.

 

Vic

When you are in a turn at 22fps, if you look at the terrain beneath you, it renders at a constant rate, but the terrain rendering during rotation is almost at a slide show level. For turns at low altitude to see the terrain passing under you as you would in the real world, we need much higher frames at least 35+.

This is a statement in the obvious. Sorry if you misunderstood me I am not arguing about smoothness. I am arguing about rendition at 22fps. 22fps is acceptable in a straight line and light turns and that is about it.

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1 hour ago, glider1 said:

When you are in a turn at 22fps, if you look at the terrain beneath you, it renders at a constant rate, but the terrain rendering during rotation is almost at a slide show level. For turns at low altitude to see the terrain passing under you as you would in the real world, we need much higher frames at least 35+.

This is a statement in the obvious. Sorry if you misunderstood me I am not arguing about smoothness. I am arguing about rendition at 22fps. 22fps is acceptable in a straight line and light turns and that is about it.

Movies have been made at 24 FPS for decade after decade and many still are, with dog fighting aircraft, race cars etc... Didn't seem to be a problem at all. 

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30 minutes ago, Bobsk8 said:

Movies have been made at 24 FPS for decade after decade and many still are, with dog fighting aircraft, race cars etc... Didn't seem to be a problem at all. 

At 22fps, bank your aircraft at 45 degrees and look out the low facing window at the scenery below. Compare with the same situation at 35fps. Which approximates the visual reality of being in a turn better? That is all I am saying.

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12 minutes ago, glider1 said:

At 22fps, bank your aircraft at 45 degrees and look out the low facing window at the scenery below. Compare with the same situation at 35fps. Which approximates the visual reality of being in a turn better? That is all I am saying.

Been doing that a great deal today in my copter doing pedal turns which are a great deal faster than a fixed wing  aircraft banking. Don't see any issue, and I am locked at 22 FPS. 

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On ‎23‎-‎04‎-‎2017 at 4:06 AM, glider1 said:

It is weird that we now think 22fps is acceptable since it is smooth. In reality, we need much higher than that (35+) at low altitude because when the plane is in a tight turn, the terrain needs to rotate smoothly. 22fps cannot achieve that by simple arithmetic unless you mainly fly in a straight line at low altitude.

Have had similar experience. I have found anything above ~45 fps desirable as that removes the jittery sensation for the most part when panning, but happen to get a taste of it only at cruise. At ~30 find it fairly acceptable not happy with, but below ~25 begins to bother. During airliner landings at large airports since most of the time looking straight ahead with minimal panning, even ~17fps didn't give that noticeable a hindrance.

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Sigh - here we go again.

IF your sim is smooth and looking good at 22 it will look just as good in the turns. IF it does not and you need 45fps to look good - your system is not configured properly BUT it is YOUR system and if you are happy with it - enjoy.

But I can do 360 degree turns around a point in P3D att 22fps with no problems.

 

Vic

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This discussion is coming up every now and then.

There are people saying they have a smooth experience at frame rates as low as 20 fps or even lower. Other people are saying they need 30 fps or more or they can even see a difference between 30 fps and 60 fps.

 

Unfortunately the most essential aspect most of the time is missed.

No matter how high the fps are, everything that appears on a screen always is a sequence of single frames. The perception of a smooth movement in the end is an optical illusion created by the eyes and the brain. The most important part of the „system“ in this regard is the user's brain.

https://en.wikipedia.org/wiki/Frame_rate

https://en.wikipedia.org/wiki/Motion_perception

At what frame rate the brain is capable of creating the illusion of a smooth movement is highly individual and depends not only on biological prerequisites but also on training, habituation and focus.

It is just like the famous picture where you can see a young or an old woman depending on what your brain is focussed on.

http://psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/perceptual_ambiguity.html

Some people see the young woman, others see the old woman. After some training most people are able to „switch“ between them.

 

With single frames or smooth motion it is the same. If the brain concentrates on seeing single frames it will most probably see single frames. And the more the brain tries and trains to recognize single frames the more it will be able to do so. The frame rate at which single frames are perceived gets higher and higher. In the end the brain might even be able to see a difference between 30 and 60 fps. While this might be an impressive ability of the eyes-brain-system – it ruins the sim experience.

But the brain can also be trained and habituated in the other direction. If the brain focuses on perceiving a smooth motion it will probably see a smooth motion. The more the brain tries and trains to perceive a smooth motion the lower the frames can get for the brain to manage to do so. In the end the brain might be able to perceive a smooth motion even under 20 fps. Those are happy simmers.

 

Of course the less movement of the scene the easier it will be for the brain to perceive a smooth movement. Without any movement at all even 1 fps is „smooth“. Looking at a tennis match (with a fast moving ball) 60 fps might not be enough. That is why „stutters“ are most easily perceived when flying low, fast and turning sharply. So when flying a B747 most probably a lower fps rate will do than when doing aerobatics.

And apparently the brain can hardly perceive a smooth motion if the frame rate is unsteady. The brain needs a steady frame rate to create the optical illusion of a smooth movement. That is why it is essential to have the sim run at a steady frame rate (by limiting the fps in the sim or by using VSync and the the refresh rate of the monitor).

 

What frame rate is the lower limit for the brain to be able to create the illusion of a smooth movement will probably be individually different and depending on training and habituation. Since movies have been shot at 24 fps for decades without people complaing about stutters that might be a good hint that the average brain is able to create the illusion of a smooth motion at 24 fps.

 

After all a recommendation for those who now need 30 fps or more (and still see stutters or would like to increase their graphic settings) might be:

- Set the sim rate to something between 20 and 25 fps.

- Adjust the sim settings so that this frame rate is achieved steadily.

- Stop looking at the sim rate.

- Stop looking for stutters.

- Try to see a smooth movement and enjoy flying.

The brain will adapt to that frame rate over time. Not within minutes or hours. It takes weeks or even months.

After a few months of habituation most people would probably be able to enjoy a smooth sim at around 20 fps (except for inevitable lags when complex new scenery / textures get loaded).

 

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5 hours ago, RALF9636 said:

This discussion is coming up every now and then.

There are people saying they have a smooth experience at frame rates as low as 20 fps or even lower. Other people are saying they need 30 fps or more or they can even see a difference between 30 fps and 60 fps.

 

Unfortunately the most essential aspect most of the time is missed.

No matter how high the fps are, everything that appears on a screen always is a sequence of single frames. The perception of a smooth movement in the end is an optical illusion created by the eyes and the brain. The most important part of the „system“ in this regard is the user's brain.

https://en.wikipedia.org/wiki/Frame_rate

https://en.wikipedia.org/wiki/Motion_perception

At what frame rate the brain is capable of creating the illusion of a smooth movement is highly individual and depends not only on biological prerequisites but also on training, habituation and focus.

It is just like the famous picture where you can see a young or an old woman depending on what your brain is focussed on.

http://psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/perceptual_ambiguity.html

Some people see the young woman, others see the old woman. After some training most people are able to „switch“ between them.

 

With single frames or smooth motion it is the same. If the brain concentrates on seeing single frames it will most probably see single frames. And the more the brain tries and trains to recognize single frames the more it will be able to do so. The frame rate at which single frames are perceived gets higher and higher. In the end the brain might even be able to see a difference between 30 and 60 fps. While this might be an impressive ability of the eyes-brain-system – it ruins the sim experience.

But the brain can also be trained and habituated in the other direction. If the brain focuses on perceiving a smooth motion it will probably see a smooth motion. The more the brain tries and trains to perceive a smooth motion the lower the frames can get for the brain to manage to do so. In the end the brain might be able to perceive a smooth motion even under 20 fps. Those are happy simmers.

 

Of course the less movement of the scene the easier it will be for the brain to perceive a smooth movement. Without any movement at all even 1 fps is „smooth“. Looking at a tennis match (with a fast moving ball) 60 fps might not be enough. That is why „stutters“ are most easily perceived when flying low, fast and turning sharply. So when flying a B747 most probably a lower fps rate will do than when doing aerobatics.

And apparently the brain can hardly perceive a smooth motion if the frame rate is unsteady. The brain needs a steady frame rate to create the optical illusion of a smooth movement. That is why it is essential to have the sim run at a steady frame rate (by limiting the fps in the sim or by using VSync and the the refresh rate of the monitor).

 

What frame rate is the lower limit for the brain to be able to create the illusion of a smooth movement will probably be individually different and depending on training and habituation. Since movies have been shot at 24 fps for decades without people complaing about stutters that might be a good hint that the average brain is able to create the illusion of a smooth motion at 24 fps.

 

After all a recommendation for those who now need 30 fps or more (and still see stutters or would like to increase their graphic settings) might be:

- Set the sim rate to something between 20 and 25 fps.

- Adjust the sim settings so that this frame rate is achieved steadily.

- Stop looking at the sim rate.

- Stop looking for stutters.

- Try to see a smooth movement and enjoy flying.

The brain will adapt to that frame rate over time. Not within minutes or hours. It takes weeks or even months.

After a few months of habituation most people would probably be able to enjoy a smooth sim at around 20 fps (except for inevitable lags when complex new scenery / textures get loaded).

 

Same thing happened with TV, and a person seeing flicker in a TV image due to the refresh rate. The NTSC system in the US used 30FPS ( actually 29.95) and in Europe, it was PAL at 24 FPS. People traveling from the US to  Europe, would complain that when they watched TV in Europe, the image seemed to flicker. After a couple of days, they got used to the 24 FPS and didn't noticed any flicker.   

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The 24Hz TV image appeared to flicker In the UK because it was beating with the 50Hz lamp frequency. Back then, phosphor persistence prevented flicker within the image, along with retina image persistance. This is why CRT monitors took to using 70Hz to 90Hz to help prevent that beating, especially with striplamps.

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15 minutes ago, SteveW said:

The 24Hz TV image appeared to flicker In the UK because it was beating with the 50Hz lamp frequency. Back then, phosphor persistence prevented flicker within the image, along with retina image persistance. This is why CRT monitors took to using 70Hz to 90Hz to help prevent that beating, especially with striplamps.

Not my experience, even in a totally dark hotel room, co workers that traveled with me to Europe a few times a year, all video professionals, would complain about the flicker in a dark hotel room when watching PAL TV. After a day or two, they didn't notice it. BTW, pro Video was my field during most of my working career. 

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4 minutes ago, Bobsk8 said:

Not my experience, even in a totally dark hotel room, co workers that traveled with me to Europe a few times a year, all video professionals, would complain about the flicker in a dark hotel room when watching PAL TV. After a day or two, they didn't notice it. BTW, pro Video was my field during most of my working career. 

Then I suspect you would know about the beating problem.

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In the CRT days the image was also interlaced, and with the phosphor persistence gave rise to smearing and making it hard to notice stagger during panning. A complicated problem with low persistence digital panels arises because the location of objects in each frame is very clear, panning can be a big problem. Extreme example of image persistence was with the moon footage where the horizon could be seen through the space suit.

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P3D is different to FSX as it has functions applied to the image to improve effects like fog which can appear very slightly behind the scenery position in a fast turn or roll and appear to look like stutter. So where FSX can work well with 20fps, P3D may not work so well at low fps, especially with stunt aircraft requiring 30+fps. In a sedate aircraft I'm using 19fps locked on a 59Hz monitor.

 

P3D is also different to FSX in that it utilises the desktop view and places a D3D image in a window. In full screen this is just a desktop sized window with caption and borders removed. The P3D display setting VSync=On will limit the fps to the refresh rate of the monitor. This may be too high to serve any purpose on a high frequency monitor, giving rise to smooth looking P3D with big monitors that only do 30Hz and stutter on monitors running at 60Hz or more. The NVidia controls allow a profile to be made to allow 30 fps or other, effectively limiting the monitor frequency but can look poor when moving the mouse around.

 

Problems are reduced by ensuring the sim can run at a very consistent frame rate, using locked fps requires a lot of power since it creates look ahead frames. It's a mistake to think that if we can see 40fps unlimited we can use 30fps fixed. In fact any tiny amount of delay and a look ahead frame is used up, with only 40fps available would take many frames to build back the look ahead frames making it useless unless we can see 60+, even 90fps would work nicely with 30 fixed.

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Having noticed slight lack of fluidity in several games even with constant 60fps+vsync using borderless window mode which become perfectly smooth on switching to exclusive fullscreen makes me think it might have its own share of micro stutters in p3d despite the triple buffering in addition to from fluctuating and low fps.

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Yes, with exclusive mode the frame does not have to coincide with the monitor refresh frequency to remain smooth, with the desktop we have to improve the coincidence by using methods to keep the frame rate consistent and using sub multiples of the monitor frequency, for example 15 20 30 or 60fps on a 60Hz display.

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