FSX-MS Is the Fiber Frame tweak only effective if FPS is limited internally?

[Afterburner 374]

Hello everybody,

 

When it comes to optimizing FSX' performance, some of the recommended tweaks are to alter the Fiber Frame Time Fraction in the fsx configuration file. There is also a frequent discussion about whether to limit FPS internally or externally for a smoother flight experience. Some users report that using an external limiter causes more blurries, while many others experience a drop in FPS when using the internal limiter. In my experience, the drop can be quite substantial at busy airports. Whereas running FSX with unlimited FPS yields around 22FPS at KORD with lots of traffic, limiting FPS internally to 30 (or any other value) reduces the FPS to 14 on my computer, which is a huge percentage loss. I was wondering why the internal limiter would put so much strain on the FPS, even though the graphics did not seem different.

 

As far as the Fiber Frame Time Fraction tweak, it is supposed to adjust the "fraction" of CPU processes that are dedicated to rendering the terrain and scenery (that's how I understand it). Playing around with different values didn't make much of a difference, until I was baffled by an unexpectedly low frame rate during cruise on one of my flights with the Majestic Q400.

 

I use ORBX Global + OpenLC EU, and it often happened to me that textures became blurry on approach with autogen objects popping up very late. Increasing the FFTF value (default is 0.33) was supposed to sharpen the textures quicker, but the difference I saw was marginal, if any at all. At this point, I was running FSX at unliimited FPS. One time I increased FFTF to 1.0, but I had a hard time finding a significant improvement. Another time when I was at cruise altitude (having 40 FPS), I limited FPS internally to 30, and to my shock, the FPS plunged to 16 or so, even though I was still cruising at 19000 feet. However, it looked like even from that altitude, the FSX was generating autogen objects on the ground (a quick switch to top-down view showed crisp textures and all objects). On approach and landing at LFPG, FPS showed a one-digit value, and I thought that this was not normal behavior. Studying my fsx.cfg, I found out that the FFTF value was still set at 1.0. I was wondering whether there was a relationship between activating the FPS limiter and setting different FFTF values. This is when I figured out that apparently, this tweak shows no effect when FPS is set to unlimited.

 

I ran a test to check the initial FPS on the runway of a selected mid-size airport (KGSP) at different FFTF values with both limited (99) and unlimited FPS. Here are my results (the FPS values indicate approximate ranges):

 

     FFTF value          FPS limited          FPS unlimited

              1.0                   34-35                     70-74

(default) 0.33                 56-58                     70-74

              0.25                 60-62                     70-74

              0.20                 60-62                     70-74

              0.10                 67-70                     70-74

              0.05                 70-73                     70-74

 

Let me also add that when limited internally, the FPS hit occured regardless of whether I would set the target FPS to 60, 99 or any other value. This result shows to me that the FFTF tweak is only effective if the internal FPS limiter is activated. When FPS are set to unlimited in the graphics option, the sim apparently behaves like it is running on a very low FFTF value. This explains why the sim is prone to blurries if FPS are not limited internally or limited externally, as reported by many users. It also explains why many users who don't apply the FFTF tweak see a huge FPS drop when they use the internal limiter - that's because the default value is set quite high. Even though these tweaks have been known for years, I thought that you might still be interested in these findings. You now know that in order to lessen the impact of the internal limiter on FPS, the FFTF value needs to be reduced. If the simulator can't reach the set target FPS, you will likely see blurries and/or late autogen rendering. I have experienced that if the target FPS is below of what your PC is capable of running at unlimited FPS, the resources will be spent more on scenery, and textures will be adjusted to look sharp quicker. If you run at unlimited FPS, then apparently FFTF has no effect.

 

If you are interested, you can try that experiment on your computer and let me/us know if your FSX shows the same behavior.

[cianpars 1,165]

I've found on my rig (fps limited to 30) that the higher I set my FFTF, the sharper the textures and the lower the framerate.  I think stuttering increases to - I've tried between 0.8 and 1.5 to this effect.

 

Some recommend 0.1, but for me, that takes away the sharpness and I've found that for performance, 0.25 to 0.45 is best for me and for sharpness, without losing too much performance, around 0.8.

 

I've just checked my fsx.cfg and found I was using 0.33, but it's commented out meaning I have reverted to default, I think.

 

IAN

[Dirk98 354]

 

Some recommend 0.1, but for me, that takes away the sharpness and I've found that for performance, 0.25 to 0.45 is best for me and for sharpness, without losing too much performance, around 0.8.

 

IAN

 

Is it 0.25 to 0.45 or around 0.8?

 

Thanks,

Dirk.

[cianpars 1,165]

Very much depends on your rig.  What's good for me may not be what is best for you.  You need to experiment to see which suits you the best. 0.25 to 0.45 for me, though I can get away with 0.8, but prefer to keep it a bit lower.

 

It's a performance v sharpness trade off which depends on system.

 

You may also find mileage can vary dependant upon the type of scenery you use.  I think when I was using Tileproxy, Christian Buchner recommended 1.5.  Photoscenry seems to benefit most from higher settings, non-photo scenery, you may find that 0.25 is OK or even 0.1 in some cases.

 

IAN

[Bert Pieke 7,585]

FSX default is 0.33