Sign in to follow this  
Bobsk8

Be careful with the FFTF tweak.

Recommended Posts

I have just been flying P3D a shade over a week and love it. yesterday however was one of those days that reminded me of my old MSFS trouble shooting days.First, I had made a couple of changes to the P3D cfg file, which included the FFTF change.   After doing this, and changing some of the settings in P3D I was able to crank up my My Traffic settings and Active Sky NG and get a solid 30 FPS just about everywhere including the New York and Boston areas, so I was pretty pleased at the way P3D is working. 

 

Last night I decided to fly VFR from KBOS to KLGA, and took off from Boston in my A2A C 172.  The first part of the flight went with no problem, but when I got down to the eastern Long Island area, I pulled up the map im my A2A 172, and tried to change the zoom setting to read a VOR, and the map went Black. At about the same time my Mindstar GNS 530 stopped showing the airports and terrain and went dark except for the track line of my course. I closed and opened the map a couple of times, and eventually the display came back and the GPS started displaying again, but trying to change settings on the map again produced a blank map and GPS display. It looked like this. My GPS would show airports, I would open the map and hit zoom on the map, and the map would go dark and the GPS would go dark a few seconds later.  

 

2015-5-12_18-40-58-638.jpg

 

As I got close to Laguardia airport, the map just refused to display the airports or terrain, and seemed stuck when it did, a few  miles behind where I had just traveled. The GPS didn't even show LGA or Kennedy Airport, except infrequently when it would pop up, as I cycled the map on and off. As I got on about a 6 mile final to LGA, I looked at the ground and it looked like a swamp, and I grew up right near there, and that is filled with homes and roads, not a swamp, so now I see I have a problem with the scenery too. Ok now time to trouble shoot, but where to start. At first I thought it was a GPS issue, since the GPS was intermittent, and not knowing how the GPS and A2A map work together, my thinking was maybe the map display get's it's info from the GPS. So I uninstalled and reinstalled the GPS, and wound up with the same thing. Now I am thinking maybe my A2A C 172 is faulty, so I tried flying the A2A Cherokee in the same area, because it has the same map and GPS in it.  This produced the same problem. Now I am thinking that the two aircraft that were installed separately could not have gone bad with the same symptom at the same time. I did notice one thing in trying to troubleshoot this problem, if I placed P3D in pause, the GPS and the Map worked perfectly. As soon as I came out of pause, it became faulty again. 

 

Before I retired, my profession included training component level techs on how to troubleshoot complex systems, and my Golden rule was always " If you suddenly run into a problem, go back to what you did last to make it worse" . I then remembered that the day before, I had made these tweaks to P3D because I am now convinced that P3D is where this problem is happening.  So I started checking on them one at a time, thinking that I would remove the tweaks to see if they had any effect on my problem. The first one I looked at was the FFTF tweak in the P3D.cfg file.  It was supposed to read  FIBER_FRAME_TIME_FRACTION=0.01 .   When I looked at it, this is what I saw FIBER_FRAME_TIME_FRACTION=0.00    I had mistyped the numbers when I added this to the P3D.cfg and changed it from 0.1 to 0.0 by mistake. This has something to do with the scenery loading time, and I had changed it to zero.  This is why the GPS, the Map and sometimes the scenery as it did when flying into Laguardia giving me a swamp, would not load. So the result was a blank display on the GPS and map, and not updating when flying, or when changing settings on the map, it not being able to update to the moving scenery position.  When I paused P3D. then it had time to load the new position, both map and GPS, so everything worked normally.  

 

​Anyway, it was a good learning experience, and shows that Pilot Error can always rear it's ugly head. . 

Share this post


Link to post
Help AVSIM continue to serve you!
Please donate today!

If you remove the entry completely - do you have the same behavior?

 

Reason I am asking is the FFTF defaults to 0.33 if there is NO entry. I SEEM to recall someone mentioning that setting it to 0.00 would ALSO default to 0.33.

 

If you run fine with no entry then it would indicate that p3D will try to use whatever setting that is >= 0.

 

Vic

Share this post


Link to post

That was good thinking to recheck your last edit, and I'm glad you spotted the error. The following is not directed to you specifically, but rather to the entire community...

 

Honestly, I've never figured out the logic of thinking that by giving the computer less time to accomplish its assigned tasks that the end results are going to somehow magically be better...

 

The value of FIBER_FRAME_TIME_FRACTION represents a balancing act; one in which the sim allows the computer just enough time slice to accomplish its assigned tasks before spewing the combined results down the road to the video card. :Nerd:

Share this post


Link to post

Honestly, I've never figured out the logic of thinking that by giving the computer less time to accomplish its assigned tasks that the end results are going to somehow magically be better...

 

Have you actually tried it? it works! Maybe not for some, but definitely for most who have tried it. It's not magic my friend.

Share this post


Link to post

Robert, yes I have "tried it" but more to the point I fully understand precisely what the parameter is for, and moreover just how it is coded in the sim.

 

I also know that the lowest possible fraction is 0.1, and that is simply not enough time for all of the events to be processed completely.

 

Perhaps it would be easier to mentally translate the fraction to a percentage. Default is to give the processor 33% of any time slice to complete the threads assigned to it. Giving it only 10% of the time slice is going to severely curtail thread task processing.

 

A more reasonable range for 'tweaking' probably would be from 20% to 40% (0.2 > 0.4).

Share this post


Link to post

I let my eyes do the talking and 0.01 -> 0.10 gives me the best results and frame rates. I see it as actually giving the CPU more time to process other events while the GPU does its thing.

 

Again, proof is in the eye of the beholder and this beholder finds the magic trick to be quite real.

Share this post


Link to post

Well, you are correct in that one aspect at least. If you are happy, then all is well.

 

The trick with FFTF is you have to have the right balance...

 

too high and you get frame rate issues and missing frames...

 

too low and you get a ton of blurries and other problems as there is not enough time to complete the tasks of pre-loading scenery.

Share this post


Link to post

OK, I am pretty computer literate, but have no idea whatsoever what this tweak accomplishes in P3d. I do know that when I placed it in the config file and restarted P3D I had about a 20% frame increase, and was able to crank up my My Traffic AI settings quite a bit, and still stay around 30FPS in 95% of the areas I fly in. No blurries at all even in areas like Metro New York City. 

Share this post


Link to post

I let my eyes do the talking and 0.01 -> 0.10 gives me the best results and frame rates.

 

 

The trick with FFTF is you have to have the right balance...

 

If I had to choose between a MilViz developer and a man with talking eyes, I know who my money would be on!

 

...I kid, I kid! sorry.

Robert, what CPU/GPU are you running? I found FFTF at extremely low settings gave me a nice FPS boost and no noticeable degradation in quality but since upgrading my GPU, the same FFTF caused extreme blurring of the terrain (it would take literally *minutes* for it to catch up) and I figured the slight FPS boost wasn't worth the blurring so now it sits at default 0.33

 

A lot of P3D/FSX tweaks are so system-dependent it's unreal and the only advice to give is to have a go and see if it works for you.

Share this post


Link to post

FFTF is only used when one locks frames via the limiter.

 

For my setup when running 30Hz, then Unlimited + Vsync + triple buffer seems to provide the most fluid experience (most consistent time between frames) for me.  If you run 60Hz then you'll need to be able to stay above 60 fps everywhere at Unlimited + Vsync + triple buffer.

 

Personally I'd never lock frames and never use FFTF ... but FFTF = 0.01 is similar to Unlimited only you still execute the limiting code -- that extra code execution takes away CPU time.  Unlimited has less code to execute (no limiter) so will run a tad smoother with less CPU load (Vsync control is faster).

 

Cheers, Rob.

Share this post


Link to post

Only use with lock BUT and its a BIG but..if your useing orbx regions or OLC and see blurring, try .1 or .2 and if they do not resolve then delete and that like setting .3

 

Also you could try with blurring

[Display]

TextureMaxLoad=30
 
[TERRAIN]
SWAP_WAIT_TIMEOUT=30
 
I use both.

Share this post


Link to post

FFTF is only used when one locks frames via the limiter.

 

For my setup when running 30Hz, then Unlimited + Vsync + triple buffer seems to provide the most fluid experience (most consistent time between frames) for me. If you run 60Hz then you'll need to be able to stay above 60 fps everywhere at Unlimited + Vsync + triple buffer.

 

Personally I'd never lock frames and never use FFTF ... but FFTF = 0.01 is similar to Unlimited only you still execute the limiting code -- that extra code execution takes away CPU time. Unlimited has less code to execute (no limiter) so will run a tad smoother with less CPU load (Vsync control is faster).

 

Cheers, Rob.

Didn't know this was only used when locking the FPS and that using it when running unlimited FPS could even make things worse.

 

Great info Rob, thanks!

Share this post


Link to post

Didn't know this was only used when locking the FPS and that using it when running unlimited FPS could even make things worse.

 

Let me clarify,  you can have a FFTF value set, but it will have NO impact if you have a Target set to Unlimited.  Doesn't make anything worse.

 

IMHO, the best method to use is decided by your monitors refresh rate:

 

60Hz monitor - 30-50 FPS use Lock + FFTF value

60Hz monitor - 65-80 FPS use Unlimited + Vsync + Triple buffer

30Hz monitor - 30-50 FPS use Unlimited + Vsync + Triple buffer

 

NOTE: some systems may not work well with Triple Buffer, but in my situation it does help smooth out the experience.

 

Cheers, Rob.

Share this post


Link to post

Let me clarify,  you can have a FFTF value set, but it will have NO impact if you have a Target set to Unlimited.  Doesn't make anything worse.

 

OK, I thought you said below running unlimited will use less CPU vs using a very low FFTF value but maybe I misunderstood then. Anyway I've now removed the FFTF=0.01 tweak since I'm always running unlimited FPS.

 

Personally I'd never lock frames and never use FFTF ... but FFTF = 0.01 is similar to Unlimited only you still execute the limiting code -- that extra code execution takes away CPU time.  Unlimited has less code to execute (no limiter) so will run a tad smoother with less CPU load (Vsync control is faster).

Share this post


Link to post

 

 


OK, I thought you said below running unlimited will use less CPU vs using a very low FFTF value but maybe I misunderstood then.

 

I probably should have worded it better.

 

Cheers, Rob.

Share this post


Link to post

I probably should have worded it better.

 

Cheers, Rob.

But it's still true there's no need for this tweak when running unlimited FPS, correct?

Share this post


Link to post

 

 


But it's still true there's no need for this tweak when running unlimited FPS, correct?

 

Yes, that's correct.

 

Cheers, Rob.

Share this post


Link to post

Yes, that's correct.

 

Cheers, Rob.

Got it, thanks Rob!

Share this post


Link to post

 

 


Yes, that's correct.

 

Truly sorry Rob, but it is absolutely NOT correct.

If FIBER_FRAME_TIME_FRACTION is set to 0.0 while using unlimited frames, the following will happen:

 

1. Autogen BUILDINGS do not get loaded (trees will be)

2. There will be minutes of gaps relatred to terrain loading (apart from the initial load)

 

So no, you were mistaken, as FFTF is also working when using unlimited frames.

 

Potroh

Share this post


Link to post

 

 


So no, you were mistaken, as FFTF is also working when using unlimited frames.

 

No need for apology, correcting or challenging information in a polite manner is part of the process and good for all.

 

I was passing along information I got from LM.  

 

For my own testing with FFTF I saw no changes at all (I was looking at Time between frames data) with FFTF values from 0.01 to 0.99 when I was set Target to Unlimited.  The only time I saw significant changes in time between frames was with Target = locked frame that was higher than I could achieve consistently.  I must admit, I didn't test FFTF = 0.0 case ...

 

I just tested the FFTF = 0.0 and sure enough the Autogen buildings do not load and Terrain loading is slow.  However, all other values 0.01 to 0.99 show absolutely no difference on my setup when Unlimited + Vsync is set.

 

I'm not sure I'd say FFTF is working with unlimited just because the 0.0 case ... don't know enough about the code to determine that.

 

I do agree that FFTF = 0.0 is causing some evaluation even when set to unlimited which I didn't expect.  But for other cases I honestly don't see any value > 0 and < 1 making any difference to time between frames for Unlimited.

 

Are you see difference when using Unlimited + Vsync with FFTF values other than 0.0?

 

Cheers, Rob.

Share this post


Link to post

Rob, as I mentioned earlier in the thread, 0.01 just gave me huge "blurries" on the terrain textures with unlimited set. I'll post a couple of comparison screenshots sometime soon to explain it better. It doesn't really make much difference when you're up at 30,000 feet but you can definitely see it at a lower altitude.

 

On reflection, this actually makes sense. This is not aimed at you Rob, just in general...

As you fly closer to a 'bubble' of terrain, the LOD improves and the textures are loaded at a higher resolution the closer you get. With FFTF set very low, the engine reduces the priority of this terrain texture loading. if you pause the sim and look at the terrain directly below the aircraft, you can actually see it loading the higher resolution textures as real time passes, although this can take upto a few minutes. I found it really jarring. (I think technically it has to do with Mipmapping, but it's all a little over my head! :))

 

Setting FFTF to 0.01 would definitely help on lower-end systems with low res textures etc. but if you're on a decent system using medium-high settings, there's hardly any difference in performance with anything other than 0.33. This is just my opinion by the way, it's what I saw on my own system.

 

I'll give it another go with the frame limiter set.

 

By the way, I find things like this funny. posted by NickN of 'Bible' fame...

 

 

bozos who claim FFTF=0 works are idiots..  that forces a .33 or default

http://www.simforums.com/forums/thanks-nick-for-your-bible_topic52380_page2.html

 

The moral of the story is, if you're tweaking and thinking 'nah, changing that value will never work' just *try it* and see for yourself. That's how come we now know about things like OPTIMIZE_PARTS

Share this post


Link to post

 

 


Rob, as I mentioned earlier in the thread, 0.01 just gave me huge "blurries" on the terrain textures with unlimited set.

 

Interesting, that does seem to indicate that FFTF is being used ALL the time regardless of Unlimited or Lock ... perhaps I need to revisit the information I got from LM ... maybe I misunderstood and my own testing is skewed based on my settings and CPU performance.

 

Certainly will add this to my P3D notes doc and maybe beg for clarification at the source.

 

Cheers, Rob.

Share this post


Link to post

 

 


I was passing along information I got from LM.


Are you see difference when using Unlimited + Vsync with FFTF values other than 0.0?

 

No problem Rob, it happens and it's surely understandable - part of the game...

Some weeks ago (when I saw folks coming up with the 0.01 tweak) I also did some tests and on my high-end system, the results were as such:

1. I never use anything else but unlimited frames, as according to me (and in sync with some old Aces friends, who did that) the internal limiter is buggy and is a bad part of the original code. (One can easily see that it is not only limiting the upper part of the max value, but also lowers the average frame-rate considerably).
So sorry, I can't speak for either Vsync or t-buffer and the like...

2. Thus, using unlimited AND putting the FFTF value at 10.0 (well above the default into the skies) you can observe the terrain loading, autogen loading and also loading the higher or highest mipmaps of the terrain tiles MUCH faster and almost perfectly. BUT it also introduces constant and almost permanent stutters at the same time. (even one sec actual stops occasionally...)

3. At the other corner, lowering the value to 0.01 results better framerate and overall fluidity, but every terrain element gets loaded rather late. One will perhaps never see the original bitmap getting depicted (apart from highest mip-map of it).

4. So there IS a difference, but it seems to be very little between values 0.01 and any of the high integers. I also checked if the changes were gradual between the values, and they seem to be just that, although the visible differences truly need large fractional changes.

Potroh
 

Share this post


Link to post

Rob, that's what I was trying to tell you previously. FFTF does work with unlimited.

Share this post


Link to post

Rob, that's what I was trying to tell you previously. FFTF does work with unlimited.

 

Sure does Jay

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this