FSX Tip of the Week:Water slider and FPS costs

So why does FSX not render as fast as your typical FPS game?


The primary difference is the sheer amount of things we render, given a 120+km or greater viewing distance and trying to render the visible portion of the planet  within that viewing distance and not some hand-tuned level like a first-person shooter style game. We dont "know" what is going to be rendered at a particular location in FSX, and we cant "tune" the content in any specific way to address performance. Once you establish that as the fundamental difference, it isn’t meaningful to talk about "FSX seems light on shaders" vs GameX, or "FSX seems heavy on CPU workload" vs GameX.  FSX is just different.


What we do though, is let the user manipulate settings via sliders and hope they can find a level of detail and visual quality that are both "good enough to look at" and "perform good enough to fly". For the most part, this just works. For the "tweakers", though, I have been blogging on various topics to try to help people understand how FSX works and where different "sweet spots" can be found.


For instance, every one notes that water is a heavy cost, especially 2.x.  Why is that so? 


Here is a breakdown of what the water slider does:

1.x has no reflections:

·         The lowest 1.x level does the basic shader.

·         The mid 1.x level adds an animated detail texture. 

·         The highest 1.x level adds some specular effects

2.x adds a 2nd pass to get reflections and this can be a killer:

·         2.low reflects only the clouds and has a little more complicated shader – it can be a good compromise

·         2.med adds scenery, eg terrain and custom objects

·         2.hi adds Autogen (trees, generic objects ) and basically reflects the entire scene, which costs a lot


Water 1.x thus just increases the shader cost and adds sampling from more textures as you move the sliders to the right. For modern hw, thats no problem.


Water 2.x needs a 2nd pass to generate the reflection. That means rendering the world a 2nd time into a texture as a render target. Which is an obvious performance hit.


And thats just for the 1st 2.x level.


Reading my list above, with Water 2.hi the shader and rendering cost is intense and directly related to full scene complexity. So having Autogen and Scenery to extremely dense coupled with Water 2.hi has a direct negative impact on performance. Water 2.hi, like our other 2 2nd pass features ( shadows, bloom ) basically cuts your FPS in half.


Water 2.med with Scenery complexity at extremely dense and Mesh resolution all the way right means that the 2nd render pass is going to cost a lot. Lower your scenery and mesh settings, though, and 2.med might not be such a FPS killer while adding a bit more visual quality.


Water 2.lo renders only the clouds and the skybox on the 2nd pass, and can be a very good compromise. And in general when over water its mostly the cloud reflections you see except at the shoreline. So this choice doesnt sacrifice too much visual quality and is FPS friendly.


Understanding this lets you make intelligent choices. Water 2.lo with high Autogen and high Scenery is much better than any other Water 2.x because 2.lo doesn’t render the terrain or Autogen.


 You have to understand FSX and its performance as a Socratic, holistic thing across all the subsystems and how they interact. It’s really hard to use try a simple Aristotelian breakdown as a vehicle to understanding FSX.

Comments (22)

  1. cmhodge says:


    I really appreciate this explanation! In my early testing (on the demo) I hastily concluded that 2x low and 2x med gave the same performance hit. When SP1 came out I tried 2x med but the hit was too much. Never bothered with 2x low. However, after reading your explanation I just tried it out with 2x low and it works quite well!

  2. surfsup says:


    Thank you for these continuing updates they are very helpful.

    As stated in previous posts the only way that FSX would work properly on my computer NVidia 680i, Dual Core E6700, 4 megs of ram, Vista Ultimate and 8800GTX card was to use the Largeadress fix which as you stated and are correct is buggy.

    I believe that you correctly stated some computers had no OUT OF MEMORY problems.  The following is what I think is the issue and thought that odd.

    I am now in FSX Nirvana, recently a complete operating system re-install was required, 8th and hopefully last time.

    Reading on the web that Windows Defender which is automatically installed with the setup can stop some drivers from being installed properly I decided to immediately de-activate this under Services, after Vista loaded for the first time.  

    I also deactivated Superfetch in both the registry and in the Services.  Readyboost was also deactivated in Services.   The reason being that I found with previous installations this slows down games by  loading too many unnecessary files and has very little improvement impact for office programs as the computer has 4 megs of memory.

    Previously I had only deactivated Windows Defender after a full install not on the first load up.  Well low and behold the computer runs FSX without any – ZERO – "OUT OF MEMORY" issues.  If I load nearly everthing at max all the FPS will do is slow down but never crash.  I run an easy 20 FPS limited nearly everywhere (with minor adjustments to only a few max settings); even landing at Kennedy Intl it only goes down to 15 with NY City in the distance -when set at 20 FPS limiter.

    Also no blurries at all even though the 8800GTX card has all settings at the max quality.

    So it seems Windows Defender although extensively re-written by Microsoft for Vista is the graphics driver slayer.  I am sure Microsoft will work on this issue but for the moment it is definetly not ready for prime time.  If I were NVidia and ATI I would be hopping mad as many of the graphics issues can layed at Windows Defender’s door.  Last time I did an install it also screwed up my Windows Live OneCare which I now use and am very happy with, this program has also gotten bad press unfairly in my opinion because of Defender.

    So it was not your great program after all, yes I to thought that maybe Aces’s might be covering up additional needs.  The program now works beyond my wildest hopes.  NVidia still has a couple of issues as you know but these are minor inconveniences.

    Finally I also found that turning off the user account control while installing also helped and always right clicking and installing as Administrator helped.  Windows Live OneCare was installed only after all programs were installed.  

    Running the program directly after install without applying updates until after a re-boot also seems to be vital and then shutting down, rebooting, and waiting 10 minutes after the reboot for Vista to stop chugging away at the drive before applying an update or new program.  By which I mean CPU and Drive usage go to 1 or 2% so that nothing interfers with the installs.  This was particually true for The Sims 2, which the children play, this program refuses to install properly unless the above procedure is applied.

    Sorry for the long post but there are so many of us that have and had these terrible OUT OF MEMORY issues that I thought this might help.

    Now to fly the world in this the best of all flight simulators in this the best of all simulator worlds, as Voltaire might have said.

  3. vgbaron says:

    Phil –

    This kind of info is invaluable. It’s one thing to tweak a slider and attempt to see a difference and another to have a basic idea of what is going on. Please continue this "series" of tips!!!

    Vic Baron

  4. Shel800521 says:

    2x low with very dense autogen and a mesh complexity of 38m works fantastic as long as bloom is not selected, bloom on average cuts performance by a little more than 20%. 19m mesh complexity for FSX Global users will provide the best results, 38m is perfect for fsx users which have no additional mesh addons.

    At the above settings and a frame limit of 28 fps provides a constant 25-28fps even at the busiest airports.

    Phil, after doing research on blurries the result has become apparent and is as simple as limiting the fps slider in fsx to something between 20 and 30 fps maximum. higher fps settings = higher blurries, pushing this beyond 40 fps is crazy and will cause major blurries. Setting fps slider to unlimited is great if you have 40 8800GTS 768MB cards in SLI with a 4Xdual quad core overclocked!! Doing this is not good, it limits resources within fsx and delays texture loading hense causing blurries.

    Phil, thankyou firstly for sp1 and the support after, i.e. tweaks and settings. fsx is a superb product, for users getting frames below 10 in fairly quite locations, UPGRADE, there is no other solution. for those getting CONSTANT frames above 45 in busy airports, RUBBISH.

  5. Phil Taylor says:


    Glad to hear you are running good. To defend Defender for a moment, it seems hard to believe all these ills could be lain it its feet otherwise there would be a large hue and cry about it across the industry.

  6. SilentGenie says:

    im not taking sides here but i believe Surfsup maybe on to something, you see i had a few issues with Vista and i chose to do a full re-install, Windows Defender interfered with my Antivirus (Norton 07) on booting up for the firsrt time, Windows was telling me i had no antivirus software and nortons was saying everything was tickety boo, then i installed FSX and the SP1 patch and low on behold on my first flight i got an “out of memory” issue so i looked at windows defender and it was on, so i switched it off and have never had an OOM screen since,

    Specs :-

    E6600 @ 2.40Ghz

    2 Gig PC-5300 Ram


  7. surfsup says:

    Thank you for your quick reply.  I agree with Shel800521 that limiting the FSPs gives a far smoother experience but then again you have been preaching this as often as you are able.

    I agree with you that Windows Defender might install correctly on some computers but not all.  I have an old Dell with which there is no problem with this computer running XP with all updates; but on my daughter’s 3 year old Dell Laptop the same problematic issues also occurs with certain programs other than FSX.  She does not have FSX.

    It seems to stop certain functions in some programs from working correctly.  This is also true of my Vista 680sli configuration.

    Why this occurs on some computers and not others I have no idea.  I used the same re-install procedures for each computer.

    Quick question will DirectX10 allow FSX, and other programs to access higher memory – above 2 megs, unlike DirectX 9?

  8. Phil Taylor says:


    Interesting, but this blog is not the place to get into a Defender discussion, and I am the wrong person to have it with. Lets agree to not go there.

  9. Phil Taylor says:


    we havent tried effects files to see if the D3DX bug that happens above the 2G line is fixed in DX10.

  10. SilentGenie says:

    yeah sorry about that phil, not the right time or place lol 🙂

    Phil i thought that once SP1 was out the door you would of shut your blog down but you always put aside time to answer our questions, that for me is better than any “contact us” most developers use. Thanks again

  11. Shel800521 says:


    20fps is good and 15fps is way above average at Kennedy Intl. it’s bearable, with my settings set at max, i find the same result 15fps – 17fps. Try Dense autogen, 19m mesh complexity and 60cm texture resolution, same great visual quality as on max, however my frame rate increased to 28fps on approach, 27 on taxi and between 26fps and 28fps at the gates, i have TrafficX installed with traffic density set at 70%, the experience is mind blowing, especially an early morning approach in slightly foggy weather (ActiveSkyX and FSX Global 2008 provide an incredible dimension to fsx, after all my flight took 7 hours and i honestly enjoyed every minute of the scenery besides the foggy approach of course).

    Most tips and tweaks have been modified extensively by myself, i have run to date 116 tests and spent an equivilant of 2.5 hours per test which is about 12 days. I’ve developed a booklet of 63 pages on every single tweak and how it affects each and every aspect of the slider settings in fsx, obviosly too big to fit on this blog however i will try and provide the essentials early next week. just a hint though, from extensive testings on both Vista and Xp Machines.

    both the ATI and Nvidia cards were used, Intel and AMD CPU’s, both single and multi core, overclocked rigs and super fast rigs, i found that XP provided better fps in some instances by 15%. Also try the XTreme-G 160[1].02 XP 32 bit drivers by TweaksRUs, great driver.

  12. panos95 says:

    Can you please tell me how many FPS were you getting at everything maxed out?

    Thanks a lot

  13. Phil Taylor says:


    Neither of my machines ( Single core Intel 3.8 w 2G ram + ATI X1900; Quad core Intel 2.66 w 2G ram + nVidia 8800GTX ) can run maxed out, although the Quad core can come close in some areas but not major cities.

    That really wasnt the purpose of SP1, nor is it consistent with the performance guidance I have given.

    I typically change settings depending on where I fly,what aircraft, and what I want to see. I also seldom use bloom or shadow, and instead prefer to spend my 2nd pass on water 2.lo or 2.med unless my mesh and scenery settings are turned down.

  14. Phil Taylor says:


    this blog is not support.

  15. surfsup says:


    Does this mean that if we switch off effects there should be no problems with over 2 megs?

    One question, is it a waste of resources going below 1 meter in resolution?

    Now getting mostly 19 FPS in NY City with 19 FPS as limiter, with most set at max except no shadows or bloom and traffic adjusted.  Now that’s a simulator.  I fly real planes once or twice each two weeks and it looks fuzzier from a real plane than it does in your program – great job.

    By the way my daughter learnt to read before she was 4 thanks to Sierra’s Space Quest no click and point then you had to type and spell the clue and she was determined.  So do I send you the invoice for her Ivy League education?

  16. Shel800521 says:


    Everything maxed out is not possible, can’t measure a frame rate, to put it simply, with everything at minimum besides ai traffic & cars at 100%, bloom set on and autogen at extremely dense, no chance of even getting a 10 fps.

  17. Phil Taylor says:


    good news, I hear the June DX release addresses the D3DX problem above the /2G line.

  18. jordanal says:

    Thursday, June 14, 2007 12:37 PM by Phil Taylor


    good news, I hear the June DX release addresses the D3DX problem above the /2G line.

    I know the /2G line was discussed earlier in relation to the notoreous  OOM limits on 32-bit apps.  Would you please comment on what exactly this June-update with the /2G line-fix means to FS and how it might be related to potential short-term and long-term fixes from ACES?  Thank you.

  19. Phil Taylor says:


    getting D3DX fixed means the unsupported but widely mentioned way of users changing FSX to use more than 2G will work without risk of crash.

    we are investigating, and if we find it is indeed fixed we may mark the app ourselves, making this be a supported thing.

    the OOM problem is caused by the app running out of virtual address space, this is a way to increase the available va.

  20. Tekhed says:


    I’ve been an avid follower of this blog since about the time I purchased my first MS flight sim experience in April. My first computer was the Dell XPS 710 H2C (water cooled). Equipped with the QX6700, I soon realized the short-comings of this chip and luckily for me was able to trade it in Dell’s new XPS 720 H2C equipped with the QX6800. There’s a huge difference in performance; even so, I’ve noticed they both have one thing in common.

    With all four cores open FPS suffers, even with SP1. With the 710, the bios would not allow me to choose how many cores I could run with, but with my 720 I’m able to run in dual or quad mode. In quad mode I have to bring my clock speed down from 3.76 to 3.4. In dual core mode I’m able to run at 3.76, hence better FPS rate.

    In dual core mode (3.76 MHz) every slider under the terrain tab is maxed out….AI for commercial aircraft at 80% and 65% for small aircraft (I could go more, but for realistic appearance I’ve limited it). My average FPS is 30. These same setting in quad core create a choppy experience (3.40 MHz). My average FPS is about 15.

    I’ve come to the conclusion that the chip is getting too hot to play FSX at 3.76 MHz in quad core mode; the computer restarts itself or goes BSOD.

    What are your thoughts on this and how do you believe FSX’s code is contributing?

    Thanks for every thing Phil, love the sim environment…glad I’m able to enjoy it.


  21. Phil Taylor says:


    We have moved the balance point with SP1,  true, but FSX is still CPU heavy.

    And yes that might have an impact on how much OC’ing one can do without heroic cooling measures or backing off on the OC amount.

    We will do more efficiency work in DX10, and newer CPUs with more GHz will help as well. The future is certainly not as dark as some wanted to view it last fall.

  22. MariaJ says:

    Hi guys, i’ve read lots of reviews on that Dell XPS 720 H2c and they said that it can run FSX on absolute MAX settings and achieve 27FPS.  Man i am so getting it………

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