Does anyone know why there is an fps drop in p3dv4 when switching from "unlimited" to say, locked 30?

I know, I know, the obvious answer is "because you changed the setting to a lower fps." 😄 Ha, yes. True. But I mean something different. 

I'll illustrate by using an example... Last week, I did a flight into Flightbeam's KMSP. While on the ground, sitting at the gate, with an "unlimited" frame rate set, I was getting about 35-40 fps. It consistently stayed over 35 fps. When I changed that setting to lock it at 30 fps, it actually dropped to about 25 fps, was more choppy and would never touch 30 fps anymore. 

Why could I get a buttery smooth 35-40 fps with an unlimited setting, but by changing to a locked 30fps, I could only get a choppy 25ish? Does anyone know the reason? 

This is a known issue in P3dv4 as I have read in various places and I can replicate similar results all the time. For another example, right now, I am cruising at FL370 over Missouri, USA in the PMDG 737. With an unlimited setting and vsync off, I am getting 58-62 fps in the cockpit. But the second I change to lock the fps at 60, my fps drops to 44-45. 

Can someone explain to me why that happens? Just curious...

With Locked FPS, the FFTF kicks in, which is fixed at 30% in standard unless specified in P3D.cfg.

With unlimited FPS, there is no FFTF.

This is my understanding.

Personally I never use Unlimited, blurries come in a very short time and then, no chance to get a clear scenery except by reloading the scenery (I mean Photo based scenery with lots of 3D objects/autogen, like France VFR regional sceneries).

 

Edited April 27, 20197 yr by patrice_bambou

17 minutes ago, tomcatman24 said:

Can someone explain to me why that happens? Just curious...

Many, many posts on the P3D forum regarding this.

Simply put, when you lock frames in P3D you force the sim to use FFTF (Fiber_Frame_Time_Fraction) to use a value of 0.33 instead of 0.1 for unlimited.

Why does this matter? By increasing the FFTF value, the sim is devoting more of the CPU resource to drawing scenery and rendering textures instead of just pumping out a high framerate.

9 minutes ago, patrice_bambou said:

With Locked FPS, the FFTF kicks in, which is fixed at 30% in standard unless specified in P3D.cfg.

With unlimited FPS, there is no FFTF.

This is my understanding.

 

8 minutes ago, F737NG said:

Simply put, when you lock frames in P3D you force the sim to use FFTF (Fiber_Frame_Time_Fraction) to use a value of 0.33 instead of 0.1 for unlimited.

Okay, thanks guys! I didn't realize that it adjusted the FFTF by changing that setting. That makes sense. Thanks!

I usually switch back and forth between unlimited and a locked 30 depending on the situation and the type of flight I am doing. I keep it at unlimited as often as possible because it is so much smoother and the higher frames are super smooth especially when panning the view. However, if scenery starts lagging behind, I will usually then switch to a locked 30. This system has worked well for me and I will probably continue to use it. 

But thanks for the answer. I did not realize that's what was happening. Thanks!

Edited April 27, 20197 yr by tomcatman24

If you set it to unlimited in P3D and then lock it at 30 with an external limiter like RTSS, you'll get the best of both.

Regards

FFTF Dynamic is currently on sale and will essentially do this for you, in the background.. well worth a try!

https://secure.simmarket.com/fsps-fftf-dynamic-p3d4.phtml

9 minutes ago, Bert Pieke said:

FFTF Dynamic is currently on sale and will essentially do this for you, in the background.. well worth a try!

https://secure.simmarket.com/fsps-fftf-dynamic-p3d4.phtml

Totally agree with Bert.

Myself I use Unlimited ( displays 25 hertz ) with Locked 26

FFTF on the ground : 0.01

4000 ft and up : 0.25

26 minutes ago, patrice_bambou said:

With Locked FPS, the FFTF kicks in, which is fixed at 30% in standard unless specified in P3D.cfg.

With unlimited FPS, there is no FFTF.

This is my understanding.

Personally I never use Unlimited, blurries come in a very short time and then, no chance to get a clear scenery except by reloading the scenery (I mean Photo based scenery with lots of 3D objects/autogen, like France VFR regional sceneries).

 

There is always a FFTF ...

Locked creates a look ahead buffer and  Unlimited not. 

Check your min framerate with Unlimited  in your most detailed scenery. Set your Locked framerate to half of that ..

 

37 minutes ago, GSalden said:

There is always a FFTF ...

Locked creates a look ahead buffer and  Unlimited not. 

Check your min framerate with Unlimited  in your most detailed scenery. Set your Locked framerate to half of that ..

Half of the min framerate using your most intensive scenery?  Half of max might make sense, but half of minimum rate is gonna be pretty underwhelming on most systems.

Regards

There have been several discussions on the benefits of fps locking vs unlimited, and locking outside P3D vs inside..

The simplest is to use unlimited fps, vsync off  in P3D and use FFTF Dynamic to manage the settings on the fly..

If you do want to lock, do it outside P3D, using either NVI or RTSS.

With RTSS you have the additional option of Scanline X/2 instead of fps lock which works quite well..  read the posts and test it on your system..

Another simple option is to set FFTF=0.01 in your prepar3d.cfg and lock the FPS inside the sim to the lowest value that still gives you the impression of a smooth motion.

That eliminates the FPS loss when locking the FPS inside the sim.

Some users reported blurries / slow texture loading with that setting and thus recommend the FFTF dynamic app to solve this. I never had blurries with this static setting inside the prepar3d.cfg on my system.

Just try it for yourself on your system.

 

Some people keep saying the lowest possible value for FFTF is 0.1. Again, just try 0.01 on your system and only believe what you see yourself.

 

Edited April 27, 20197 yr by RALF9636

What is RTSS?

 

Riva Tuner Statistics Server -- a graphic utility to manage video card settings, performance testing etc.

That's because of the default fiber frame time fractions settings in p3d. When unlocked the value is set to 0,01. With limited fps the value changes to 0,33. Manly giving more time per frame to the CPU to process the terrain and objects before transferring the frame to the GPU (for a correct explanationsearch in the forum).

Just add this in your prepared.cfg (location: user\your user name\AppData\roaming\lockheed matin\prepar3d v4\) and see what it does:

Go to the entry: [MAIN]

FIBER_FRAME_TIME_FRACTION=0.01

Now you get the same performance with limited fps as without. Have fun, and welcome to the world of cfg tweaks.

 

26 minutes ago, Rasterfahnder said:

That's because of the default fiber frame time fractions settings in p3d. When unlocked the value is set to 0,01. With limited fps the value changes to 0,33. Manly giving more time per frame to the CPU to process the terrain and objects before transferring the frame to the GPU (for a correct explanationsearch in the forum).

Just add this in your prepared.cfg (location: user\your user name\AppData\roaming\lockheed matin\prepar3d v4\) and see what it does:

Go to the entry: [MAIN]

FIBER_FRAME_TIME_FRACTION=0.01

Now you get the same performance with limited fps as without. Have fun, and welcome to the world of cfg tweaks.

 

And if you now start getting blurries, you know what caused it..