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GA Traffic too much of an FPS killer - and I think I have figured out why (documented)


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Hello Burkhard Renk and other MyTraffic-users,

I have recently purchased the latest edition of MyTrafficX Professional 5.4b for FSX, and I am quite happy with it!

However, I have noticed that GA traffic takes a giant toll on the framerate. Let me document it:

Let's start with the display settings of my system, which I have tweaked according to some known sources (Jesus, Kosta, etc.):




For the beginning, we are going to set air traffic completely to zero (and only leave some ground traffic):


Now I set the skies to "clear" and the visibility to 10 miles (this is why weather settings are irrelevant in that scenario). The airport that I'm going to select is default KJFK on runway 31L. I use the spot view and direct the camera at the airport buildings and terminals, where most airplanes are normally parked.

Without air traffic, the average frame rate is 41.4, which is not bad at all for the given scenery settings.


Now I increase the airline traffic slider to 100%. I know this value is extreme and unrealistic, but I do it for experimental purposes. As a side information, I will be using reduced AI airplane textures, and I have deactivated exit data for jetways and extended lights, because my PC is not that powerful. Let's see what happens:



The average frame rate is now 21.9. The performance has taken a huge toll, but it's still good in my opinion, since there are over 100 airplanes (!) present on this airport alone (you can count them using top-down view). By the way, if I use high-quality textures, I get around 13 fps. If I also activate jetways and ground services, the frame rate drops to dramatic 7 fps initially (I have tested it, but not documented with pictures). So sticking to low-quality textures and dispensing with jetways definitely helps a lot in terms of fps.

Now I set the airliner traffic slider to zero and GA traffic to 100%:



What has happened? The average frame rate is now 28. You would think that this is not too bad for such a large airport, but the problem is that there is no GA traffic visible (and there are only very few on this airport stationed).

To show that, I am attaching a picture of the top-down view, on which you see no airplanes:


(next part following in the second post, since I have reached my maximum screenshot limit)

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Out of curiosity, I have set both sliders to 100%:



Here, two massive FPS eaters join forces and push the frame rate down to 13.5. That's obviously so low that the sim is on the verge of stuttering.

Now back to the 0% airliner and 100% GA traffic scenario:

For the fact that there is no GA traffic in proximity, 28 fps is actually a bad deal. I have been wondering why, not only since GA airplanes are much simpler than big airliners (therefore require less CPU power), but also because there are almost no airplanes to display (only processing those that are farther away out of visibility).

The MyTraffic manual documents that the package uses some stock airplanes, such as Beechcraft, Cessna, Mooney Bravo, Learjet and others. And it has been known in the FSX comminity for long that stock (default) airplanes are a very huge resource hog. Could the bad performance be related to stock airplanes being used as AI traffic?

Upon clicking on "View Mode -> Air Traffic" in the menu, I realized that there were lots of Barons, Skyhawk's, Beechcrafts and Bravo's rendered - most of them stock planes. I have asked myself: What if I get rid of them and leave only those GA planes that came along with the MTX package?


Some of the tools included in the MTX 5.4b package allow the user to disable specific aircraft from being used as AI traffic, but to be honest, I have not experimented with these tools yet. Instead, I have applied a simpler method: I have removed all aircraft (except of Airbus and the Troka that I have been using) from the Airplanes subfolder inside the SimObjects-folder into a temporary outside folder. That way MyTraffic would not find stock airplanes first place.


What happens if I set the GA traffic slider to maximum now, employing the same airport szenario?



Here I get 36.1 fps on average. That's a jump from 28 fps (stock airplanes used) by factor 1.29, which I think is very considerable!

Is all GA traffic gone now? There are almost none available on this airport, but a click on the menu shows that the FSX processes some distant GA traffic - however, none of it comes from the stock airplanes.


At last, I was interested in what happens when I set both traffic sliders to 100%. Here is the result:


Around 20 fps average frame rate. I would say it's playable. Remember, the same slider combination produced 13.5 fps when stock GA traffic was rendered. Disabling the latter makes the frame rate soar by a factor of 1.48! I think this is immense.

The top down view shows that pretty much all gates on the airport are populated with airliner traffic:


Before moving on to the next part, I think it can be concluded at this point that stock GA airplanes, when used as AI traffic, are serious FPS killers that interfere with the framerate-friendly MTX airplanes.

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In the next scenario, I want to position the airplane at an airport that is not so detailed and FPS intensive as JFK.

I'm using the same airplane, but I select the Greenville/Spartanburg Intl. airport in South Carolina (KGSP). The default runway is 04. The weather is the same as before, as well as all display settings except of air traffic. This time I measure the average fps from the cockpit view of a very simple airplane.

In the first case, I have deactivated all air traffic:


100 fps on average looks like a lot, but it should be no surprise, as there is no complex scenery around and the aircraft has a cockpit as simple as can be.

Now I have moved all stock airplanes to their original folder, so that MyTraffic can use them.


I set the GA traffic slider to 100%. Let's see:



The average frame rate is more than playable, but it has taken a very huge hit by a whopping factor of 2.43!

And it comes at no reward for the visual quality or realism: The airport is still empty, as the next picture shows:


A look at the traffic menu reveals that there are lots of Barons and Bravos in operation (stock aircraft)


Now I am interested in the frame rate at 0% GA and 100% airliner traffic. Here we go:



Well, here is the irony: Despite being visible, "bigger" and filling all gates at the airport, the frame rate with 100% airliner traffic and 0% GA is higher than vice versa (even though the airport is empty then).

The top-down view shows that the relatively small airport is indeed busy with traffic:


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Now I am on to remove stock airplanes from the FSX airplanes folder, as I did before. I restart FSX, set GA traffic to 100% (and airliner traffic to zero) and load the same scenario:



Well, that's a different story! Average FPS is here 78.6 versus 44.7 with stock aircraft - that's an increase by factor 1.75!

In the menu, we still see lots of GA traffic, but none from stock airplanes:


And the final question now: What are the frames with 100% both GA and airliner traffic, without stock planes in use?



46.3 - I think it's good - in fact, it is a little HIGHER than having GA traffic only with stock planes included (remember, avg. fps was 44.7 in that scenario)!

Now to my conclusive questions: Can you reconstruct these scenarios and check whether stock airplanes also impact your computer that much? That would answer the question whether it happens on other systems, too. From the results, I suspect that it must be stock planes that cause such a fps plunge. Even though I realize that with GA stock planes removed, there is less GA traffic in operation. But still: The fact that the combination of 100% GA and IFR traffic without stock planes produces a little higher frame rate than 100% GA only with stock planes is telling and indicates to me that the stock airplanes are the culprit.

And the next question: How can I eliminate stock aircraft from all MXT plans without having to remove the aircraft from the airplanes folder inside fsx SimObjects? I assume it must be possible, but I haven't worked with the tools yet.

I would like others to test out these scenarios, too, in order to find out whether GA traffic takes a toll on their performance, too. If that's the case, maybe it would be a good idea for the developer to replace the stock airplanes with MTX' own framerate-friendly versions...

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Thanks for this detailed report. One proposal I want to make is that you always, when looking at the fps, take two numbers: One with simulation running, and one with simulation paused. The reason is that on all my tests, even at extreme locations, the CPU load it takes to move the aircraft in the reality buble is larger then the load needed to display the nearby aircraft. The load an aircraft makes that moves 100 miles away is bigger than the load an aircraft makes that you see parked nearby.

Of course you see no or almost no GA aircraft there, but the are tracked, FSX calculates the distance from ground mesh at every frame, ATC handles them, that is where I think the cycles go. If the aircraft are simpler or more detailed only makes a difference when you are very near to them.

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Okay, so I did another experiment in KGSP, and this time I have measured the fps in both running and paused modes.

The airplane is the same, and the display settings are changed only insofar as I have deactivated ALL ground traffic (service vehicles, cars, boats, ships) in order to avoid confounding of the effects on FPS in running vs. paused mode between ground traffic and air traffic.

I am just going to post the FPS range that I have measured for each slider combination without screenshots (since they are a little time consuming) (If required, I can include them later)

KGSP (Greenville/Spartanburg), Cockpit view

Stock Aircraft Included

0% IFR, 100% GA

Run 44-48 fps

Paused 70-76 fps

100% IFR, 0% GA

Run 59-63 fps

Paused 92-100 fps

100% IFR, 100% GA

Run 32-34 fps

Paused 56-61 fps

Stock Aircraft removed

0% IFR, 100% GA

Run 84-88 fps

Paused 117-125 fps

100% IFR, 0% GA

Run 59-63 fps

Paused 92-100 fps

100% IFR, 100% GA

Run 47-50 fps

Paused 86-90 fps

100% IFR, 0% GA, Hi Texture, Jetways active

Run 53-55 fps

Paused 86-91 fps

Conclusion: We can see that pausing the sim does raise the FPS indeed considerably.

However, for a mysterious reason, even when FSX is paused, the FPS at 0% IFR and 100% GA are significantly lower (70-76 fps) when stock planes are included, compared to 117-125 fps in the case of stock aircraft being removed. Remember that in both cases, almost no GA planes are visible on the airport. If it is true that most CPU power is allocated to tracking GA traffic, should the frame rates not be the same for stock planes included vs. excluded when the simulator is paused?

And I still would like to know which tool you need to use to remove stock airplanes from MTX AI flight plans.

If that happens (either one way or another): Will there be less GA traffic activity in general, or will the planes that were used by stock planes be replaced by MTX own GA planes, resulting in only little change in traffic volume?

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Thanks, since I know where you made these tests I can try to do the same and will look for the total number of airplanes - most GA is Cessnas.

If you want to modify the schedules, you can do so using the MyTraffic editor. Removal of ALL stock GA airplanes now by definition is a complex task and requires some knowledge of the editor and various SDKs.

In short, the easiest way may be to edit the types in MyTraffic editor, and uncheck the "Use in MyTraffic" check box. Whyou then run a "create schedules, files and traffic", these types will not be considered and consequently other types used.

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