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eeyore

Performance (Frame Rates) and Anatomical Biology

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Having come back to FSX (after earlier giving up on it until I had a decent machine on which to

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After many years of simming I have actually stopped looking at the FPS counter once I moved to FSX and a solid hardware platform. I remember spending so many days trying to increase the FPS number. After a constant tug of war battle with FSX I finally realized something. One day I decided not to enable the FPS counter and it was the best thing I ever did. The FPS number is not what is really important. It is the smoothness in between frames that makes the real difference, at least for me. I currently fly FSX with a lot of settings maxed out. It looks absolutely fantastic and very smooth. There are times when I lose a lil smoothness in heavy scenic areas such as NYC but you know something it is still very very flyable and enjoyable. Sometimes when Im flying and enjoying the amazing scenery and smoothness I may turn on the FPS counter to see the numbers and you would be surprised because sometimes those numbers can be anywhere between 9-15 FPS. Some time ago I would have thought oh man that is absolutely awful! I would then spend countless hours tryin to raise that magic number. I now realize that the FPS is only a small part of the overall picture. With the right hardware I think many people can fully enjoy FSX as long as they don't focus entirely on the FPS. Look at the smoothness instead I say. Just my 2 cents :)

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Not to rain on the parade, but there's a lot more to it than bragging rights, though that certainly exists here, as it does in every area of computing, and life. ;)25 FPS is fine for GA or Airliner flying, where the aircraft in question are stable by design. 25 FPS though is just simply insufficient for any kind of flying that requires very rapid and minute control inputs and responses, such as flying helos, aerobatic aircraft, close formation flying, and anything that moves at over 500 kts really.As for 25 FPS (actually 24) being the point at which the human eye can no longer detect differences in fluidity, it's unfortunately a total myth. That 'magic' number came from the film industry in its early days. At the time that standard was set (which we're oddly still using) they weren't looking for the rate at which differences in fluidity could be determined, but rather the *minimum* framerate at which movement could be considered fluid by the majority of people at all. This was simply due to the fact that back then film was a very expensive commodity.Anyway, whatever FPS floats your boat is great, but as I'm firmly in the aerobatic/helo/fighter camp I'll be satisfied with 60, if I ever get there, nothing less. :) 120 would be nice. I'd have to dig out my old CRT hehe.-mike

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I only *fly* the default airliners, with 3rd party paints, out of major airports. My FPS are, most often, well over 25, but the in/out popping and snapping of terrain textures and autogen is what ruins the experience for me. Too, Terrain textures don't fully focus until directly under the ac. Big turn off!!I have a Q6600 quad @ 3.6, and a Nvidia 8800 Ultra with 4 Gb ram on XP.Bruce

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There is another aspect to this subject. The motion of an observed object per frame. Take off on a moonlight night and head directly toward the moon. Whether your PC is going at 1FPS or 200FPS you will see no observable difference in the moon because its relative change per frame is zip. Now go and park you aircraft at a runway holding point and observe a jet landing. When the observed aircraft is directly in front of you its movement per unit time will be very rapid and I can assure you that at 35FPS(I run around at that rate)the movement of the observed aircraft will be large per frame and will not appear fluid. So the 25FPS might be OK for typical film sets where cameras can pan and reduce apparent movement between frames but flightsim is not a movie or TV studio set. Top competitive FPS players claim they can tell the difference between 70FPS and 90FPS. This is not a simple topic, claiming that 25FPS is enough is observably wrong in some circumstances. My experience is that 25FPS is OK if you are doing an approach to a runway where subject changes per frame are relativley small provided you are in an aircraft which has a relatively low approach speed. However, I have found that if flyig an aircraft with a 150Knot approach speed then 25FPS is not good enough for aircraft control purposes.

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Now you guys are fully on my turf, so I get to do a lot of explaining, a la any given James Bond villain.Film speed is closely related to the motors used to drive film through a camera and a projector. Before motors were used, film crankage was done by hand. Since film stock is expensive, many directors chose to undercrank the camera, so that it was common to see films in the 8-12 fps range. Once the process became automated, we saw projection move to around 24 frames per second (fps). This was largely due to the nature of AC current. You need AC to drive a rotary electrical motor. By timing the revolutions of the motor to the current, you get the the most efficient and smoothest drive possible. AC is different in Europe than it is in North America, which is why their film standard is 25fps and ours is 24. Film is largely irrelevant to the televised video culture (and I can got at length in very personal detail as to why this is so, but that's a different topic). Video analog signals are transmitted electrically, rather than optically. The most stable signal signal was 30 fps, which could transmit black and white images as well as sound. Again, the number is related to the transmitter (think of transmitting in multiples of MHz), rather than to any specific vagaries of human biology. When colour television was invented, the signal frequency was not aligned to travel at 30fps and provide sync audio and still be stable. So the NTSC standard comes to take away .03 of a single frame in one second. That three-one hundredths of a frame is used to encode the information television sets need for colour. The system is called 29.97 "drop-frame". The bear of it is, if you record synchronized audio at 30 fps, every second that goes by you will go out of sync by .03 seconds. Then there's PAL and SECAM which do the same thing as NTSC, but use different incompatible formats. Television is largely irrelevant to computer video culture. Since the computer renders video digitally, rather than in analog, you can freely jump between frame rates as you see fit. We are used to (nearly) 30fps, so that's kind of a benchmark of computer video. In reality, most game publishers shoot for 60fps. 60 = 2 x 30. The vast majority of people cannot see above 30fps, but that's not to say it's impossible. So why the extra unseen 30fps? It's called "overhead", and it provides a buffer of visual processing in case the game goes into a highly-detailed area. That way, the frame rate can bounce around freely between 30 and 60 fps, and the gamer won't likely see any difference. Putting on a frame rate lock can add so much stress to a processor that you will automatically slow the frame rates below optimum levels, so in many cases, if you can avoid locking frames, you do so. As to seeing above 30fps... some people claim its possible, and I do not doubt it. You can train yourself to perceive frames clearly. Some of my background is in classical animation, so I can tell you with 99%-100% certainty what your frame rate is from 1-24 fps just by looking. I can estimate 25-30 fps frame rates maybe 75% of the time. Anything above that, is just a guess for me. People who do pure video animation are usually better at estimating 30fps than me. Then there are gamers. Some of them are awfully good guessers at above 30fps. Are you one of them? One way you can tell is by fooling around with the refresh rate of your monitor. CAUTION: DO NOT SET YOUR MONITOR TO ANY RATE IT WAS NOT DESIGNED TO DISPLAY!!! If you set the monitor to a multiple of 30, then you might see some artifacts, blurring, or just get headaches. This is especially true of interlaced displays, I don't know so much about progressive scan. On an interlaced display set to 60 Hz, you will see "half" of a frame (called a "field") displayed alternately with the other "half" 30 times a second. These numbers ought to look very familiar. 30 fields a second is kind of like 30 fps. 30 fields times 2 = 60 cycles a second, which is what you see visually on a 60 Hz interlaced display.Another way you can tell if you are sensitive to frame rates above 30 is to spend time under fluorescent lights. Unlike incandescent bulbs with tungsten filaments, fluorescent lights strobe. They tend to do so past our perception, at around 120 - 180 Hz. But, we are back to those multiples of 30 again. If you are tuned to perceiving frames at 30 fps, then living under fluorescent lights will give you headaches and make you tired. It's not like Ned Flanders says, "They hum like angels! You're never lonely if you've got a fluorescent light!" It's more like a reason to take a blunt instrument to an otherwise innocent lighting fixture at five in the morning. MORE CAUTION: NEVER BREAK OPEN A FLUORESCENT LIGHT!!! IT'S FILLED WITH POISON!!! ALWAYS DISPOSE OF FLUORESCENT LIGHTS BY TAKING THEM TO AN APPROVED DISPOSAL FACILITY!!!So, anyways, I hope that helps. It seems every year someone comes up with this topic, and I always think it quaint to discuss it in the FSX forum because there are places in the FSX world you are never going to get 30 fps with the sliders on full. Jeff ShylukAssistant Managing EditorSenior Staff ReviewerAVSIM

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>This is not a simple topic, claiming that 25FPS is enough is>observably wrong in some circumstances. A respectful correction:Claiming that 25FPS is unnoticable is wrong in some circumstances. There are some who might feel that 25 is enough to be satisfied, even if it incurs some chop. :) Furthering on what Mike/Haldir/Lotus said above, the 24FPS in use by the movies has another major benefit which a computer screen has yet to bring (en masse) - and that is film/motion blur.When you take a photograph of something moving, especially moving fast, that object will often times be blurred because it is moving too quickly for the camera to take a sharp picture of it. Our brains take that blurry image, and combined with the frames before and after it, decode it into what appears to be relatively smooth motion. Our COMPUTER screens display one absolutely crisp image after another. There is no motion blur in the images, and this can be a jarring effect, especially at lower frame rates. Back in the day, 3DFX had a series of Voodoo cards who's big claim to fame was the fact they could do motion blurring, but they came out at the end of 3DFX's pioneering reign at the top of the video acceleration market, and were never widely adopted. To be honest, I'm a little surprised that the eye doctor indicated that 25 was the highest discernible rate... Oh well,-Greg

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>Claiming that 25FPS is unnoticable is wrong in some>circumstances. There are some who might feel that 25 is enough>to be satisfied, even if it incurs some chop. :) >When you take a photograph of something moving, especially>moving fast, that object will often times be blurred because>it is moving too quickly for the camera to take a sharp>picture of it. Our brains take that blurry image, and combined>with the frames before and after it, decode it into what>appears to be relatively smooth motion. You are absolutely right!This is the CRUCIAL difference: too many times over the years I've been reading this on too many forums to be able to count them...There's always someone starting the theory that, since TV and Motion Pictures use only 24 or 25 fps, this is the maximum the human eye needs to get a smooth motion.This might be correct IF computer generated images were "shoot" just like video/film frames. Unfortunately, they aren't. In video/film, there's a finite SHUTTER time, which adds the natural motion blur over moving objects (and the the camera movement as well), that our brain uses to AUGMENT the sense of smooth motion.If the shutter speed on a video camera goes too high, like at 1/1000th of a second, the result would be a noticeable jerky motion. But of course, putting the video in pause would look great, becuase you might be able to capture, for example, a fast moving race car which would have been otherwise very blurred, when paused.Also, while feature films are almost always shooted at 24 fps, a LOT of TV (I'd say most of it) is shooted at 50 or 60 INTERLACED frames, which means the indidual fields holds a temporary difference, so they hold information that will help us getting the sense of a smoother motion, at a cost of loss of vertical resolution and possibly jagged lines, but video at 50i or 60i IS visibly smoother compared to film at 24p or 25p, this means we CAN see a difference!Computer generated images, when not pre-rendered (like in animation feature films), do not have ANY motion blur, so they can be thought as film shooted with an "infinite" fast shutter speed, this means you'll need MORE than 25 fps to get the same sense of smoothness coming from a film shooted at 25 fps+motion blur.One should really have a look of the latest racing or fighting games on consoles to appreciate that. Since videogame consoles usually (not always, but usually they do) have the frame rate synched to the refresh rate of the TV, they are either running at 30 fps or 60 fps. The difference is VERY EASY to tell apart, and the 60 fps games are usually very highly regarded in the videogaming community.

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As many times as some observers say that this subject comes back to the forums, it obviously still generates responses.Search the Internet and look for the reports that have been published following various studies that have been undertaken

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>However, what we are talking about with regards>to meaningful experience and

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There's plenty of online research touching on the points raised by Umberto concerning the unique problem of motion in computer graphics.scott s..

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Great topic !Sorry for my english...If I read correctly.We / you have elected some parameters for a good moving picture.Moving blurs.Sharpe image.One give us the movement.The other the details.And what we need ?A good "balance".It's a french word, perhaps a good "mix" ?Is there any rule for that ?24 or 25 frames are / were Ok for old CRT television.But today we have LCD or (for me) CRT monitors.Devices with really precise dots.It's even more accurate for LCD.So "bluring" has to be balanced with speed.With that we can put some values.For sure it's depending to everybody percetance.But just for fun if you can.Try to put the same fly on a old classic TV and after on your "up to date monitor".It's not the same world.At the end...As simmers what we want, what we need ?CPU, yes because this sim really need it.A lot of screens ? Yes also. Hundred of fps ?Not sure...

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I find this topic interesting in that I get to show off even more! Well, that's egotistical, it's an interesting topic without me, but here goes:You can ask your eye doctor if he or she know about "geons". Geons were cutting-edge back when I was taking my degree, back in the '80's-'90's, but they still have relevance today. Basically a geon is a pre-rendered shape definition that we all carry around in our brains (so-called "wet-ware"). We have around 2 dozen geons that we can mix and match to make complex shapes that we can easily recognize. Go watch any of the "Terminator" movies and shows. The Terminator Point Of View shots (red screen with white computer overlays) were originally based on geon theory, as James Cameron's special effects gurus were big fans of the theory at the time. Geons are very similar to polygons as used by DX in PC graphics. There are polys that are hard-wired into DX-capable graphics cards to make drawing shapes easier, or at least they were in the early cards.Why talk about geons? There's evidence that geons may be the brain's preferred way of perceiving shapes, but that they are not the whole story. Geons arise from an even more basic cognitive-perceptive concept: that the brain will seek out edges and then fill in the detail of any shape it perceives. Think of a task where you decide to draw an AVSIM Colouring Book for your favourite nephew. You start by drawing the line-art of the aircraft, making the border very bold. You decide your picture is too good to give to your nephew, so you fill in the details and colour it in yourself. That's how the brain is said to work when processing image data.So then the question of smoothness of frame rate versus blurriness/crispness of objects does have a rule, and it's based on biological physiology, and we can call it geon-based perception or Recognition By Components (RBC). Does that really matter? Maybe to game or movie producers who are keen on exploiting human physiology to make a game or video(and yes, there are a few who are clever enough to do that, but it's not easy to be that smart in the long run it takes to publish a video or a game). For most of us, we do what we can to tweak the game or the sim to suit our own needs. We make these changes, it seems, based on instinct. Pretty deep, no?Jeff ShylukAssistant Managing EditorSenior Staff ReviewerAVSIM

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>fps above 25 may not actually be worthwhileThe key fact is that what FPS counter shows you is often NOT true. This is a number averaged over some short period of time so you can even read the number. This counter simply doesn't tell you the whole story.IF the frames in MSFS were coming synchronously one after another guaranteed 1/25 sec apart that would be enough for most of us to perceive smooth motion but the problem is that individual frames in MSFS are coming asynchronously with random spacing and even though the counter may show 25 fps there will be frames that are spaced much farther apart than 1/25 sec causing stutter. It would be nice if locking frames at say 25 fps would actually mean that you are guaranteed that no two frames will ever be separated by more than 1/25 sec.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

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To me, straight line flight is not really too critical.If I'm doing 30 fps, I'm perfectly fine, and can actually hang with 20-25 in most cases. To me, having the overhead is what really counts.So being able to do 60-70 in easy flight is a good bit better.Not because it looks so much smoother in straight flight,but when making turns, taxing, etc it can really help tohave the overhead so in the bad spots, you can still do atleast 20-25 or so. Another thing about a really high frame rate is the illusionof wind, and the way it looks and "feels" is more realistic to meif the frame rate can remain high.The side to side motion and bounces are more fluid.I only need about 20 fps to make a "greaser" landing with a jet in FSX. Many large airports give me less than that, and I still manage to make decent landings. But I need at least 20+ to really have it feel smooth enough to nothave perceived delays in what the aircraft is doing vs my inputs,and also have the touchdown feel nice and smooth with no clips.Of course, 30+ is that much better.. And 50+ is where I really start to notice the effects of wind, etc start to really feel andlook pretty realistic as it's more fluid.

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Just to throw another carrot into the stew-The number of retinal receptors in our eyes is fixed. Consequently, we perceive more image detail when our eyes concentrate on a small area. Often referred to as squinting- as in a single monitor 45

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You seem to mix up 2 different issues here: Frame rates and latency.Latency (also sometimes called throughput delay) is the time between an input the user makes (usually measured at the primary flight controls e.g. stick) to the last pixel being drawn of the first image that reflects the system's reaction to the user input.This latency has to be below certain values to avoid PIO and other ill effects. Though some regulations allow as much as 150ms (or even 300ms for less sophisticated devices) in addition to whatever the actual delay in the simulated aircraft is, I think anything above 100ms can be perceived.Now, a completely different issue is frame rates (i.o.w. how many new images are rendered and displayed (in the professional world the display systems and the image generators are usually synched) in a given amount of time). All professional synthetic training devices of the highest level have to produce at least 60 images per second.Motion simulated by displaying static images at this rate is perceived as fluid under most circumstances by most people. Nevertheless, depending on the scenario and the sensitivity of indivduals, higher rates may be required to completely avoid any perception of non-fluid motion.Also, there is a third issue not mentioned yet: smearing (even at 60 Hz an easily perceivable issue). Conventional displays (e.g. CRTs) and some modern scanline based systems (laser projectors) draw a picture line per line. The time that one particular line is visible is only a fraction of the time that it takes to draw a full image. It will be dark long before this particular line is drawn again as part of the next image. Our brain likes this and easily interpolates between 2 succeeding images. With other projection systems (e.g. LCOS, LCD), one full static image is shown for 16ms and then switched to another static image with no dark time in between. This is problematic as our brain can not interpolate between the 2 images. To avoid this you need to either render and project at even higher rates or artificially introduce a black frame between 2 images, usually implemented via mechanical shutters.

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One question that bothers me and I wonder if the experts can answer: What does FSX actually do when you set the frame rates within the settings to say 30 or even unlimited? Further . . . . At a setting of 30 is the sim actually sending or trying to send 30 frames per second to the monitor? What happens program and visual wise if FSX cannot send the supposed 30 frames?At "unlimited" how many frames are actually being sent to the monitor and what is that dependant on, ie cpu, ram, etc. And now to the biggie - what is the "optimum" frame rate setting in FSX that we should use? Is it a multiple of 24, 25, 60 or whatever?Aplogies, if these are very basic questions.Peter Hayes

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>One question that bothers me and I wonder if the experts can>answer: What does FSX actually do when you set the frame>rates within the settings to say 30 or even unlimited? i'm hardly an expert..but here's .02.. i think one of the phil taylor blogs (or maybe some nick n post) discussed this in detail, but if i recall correctly, the idea is if you set a fixed rate, whenever the simulation gets ahead of that speed it will use the extra time in that frame to get caught up on loading more texture details or terrain details rather than starting to render the next frame right away. at unlimited it prioritizes framerate over everything.>Further . . . . >At a setting of 30 is the sim actually sending or trying to>send 30 frames per second to the monitor? yes, in that case if it finds that a frame is done rendering faster than 1/30th of a second, instead of starting the next frame it will do other housekeeping tasks or grab some more higher-res textures etc. this can result in helping with 'blurries' or whatever. >What happens program and visual wise if FSX cannot send the>supposed 30 frames?then it's playing catch up and basically isn't acting much differently than if it's at unlimited but running slow due to whatever factors (detailed plane, lots of clouds or scenery or ai etc.)>At "unlimited" how many frames are actually being sent to the>monitor and what is that dependant on, ie cpu, ram, etc. up to a point it is limited by video card, but with anything 512mb+ like an 8800gt or better it is starting to get limited by cpu speed. when i overclocked my cpu by 10% i actually saw a pretty much linear 9-10% increase in framerate. if your videocard is relatively good it's not so much of a bottleneck although this can be affected by running very high quality aa settings and high resolutions together except on the most top end stuff.>And now to the biggie - what is the "optimum" frame rate>setting in FSX that we should use? Is it a multiple of 24, 25,>60 or whatever?basically it's up to you which feels better when you fly it, although i think you might say instead of 60 to set to the refresh rate for your monitor. the issue gets more complicated because for some people (myself at least) using a fixed framerate results in an overall reduction in average framerate. it also depends on what kinds of mods you are using and many other factors. there's no harm in just trying out different settings, although i think you'll find most people run something like 20-25 to prioritize appearance and smoothness, or unlimited for raw performance.. it also depends i'm sure on settings in your .cfg files..>Aplogies, if these are very basic questions.>Peter Hayesand apologies if my answers are off base at all. i was very interested in this thread because i have always been intrigued by the issue of how motion blur due to receptors (or film emulsion for that matter) being exposed over time affects your perception..different than discrete images like a video simulation is rendering... one thing not really mentioned is also that the physics simulation and your inputs to it seem smoother at higher framerates - i don't know how fsx does it but some engines calculate at a fixed delta and others by frame, which can lead to things like stuff snapping around on a slow frame because it extrapolates further than was expected without enough damping, (like flying with 2x or 4x time)but even with fixed intervals for physics, if your view of what is happening is across variable time intervals your ability to react is messed up.. back in 99 or so i read a study done by the military in sims where they examined the ability of pilots to react at different framerates and determined that the 60-75 range was where it stopped making as much of a difference, but anything lower than that was perceptible. that certainly bears out my personal experience with fps games and the like where if i don't have my mouselook locked at 60 i get dizzy or frustrated.. with fsx it's a little more forgiving since you aren't snapping your view 180degrees to watch your six of course, but if this was a combat sim that would be another story too lol.. i can certainly say i would rather run fsx at 60 if i could heh..cheers,-andy crosby

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CrosbyMagnificent answer - made the whole scenario much clearer. I just had to wonder why Microsoft would place a frame counter (as do other games) amd a method of changing those apparent displayed frames in FSX, when it possibly had nothing to do with the way that human beings see images being displayed on digital (and analog) visual display media ie monitors.Now my dog says he gets 400 fps in FSX no matter where he is flying. Woof! Woof!Peter Hayes

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>just had to wonder why Microsoft would place a frame counter> as do other games) amd a method of changing those apparentBecause FPS is what people know about it, what an average person understands.The only way to do it 'right' would be to dump statistics to some flat file (say every 5 minutes) that would give you comprehensive histogram of all frames that arrived during this 5 mins, grouped by intervals between them. Say there 500 frames separated by 1/25 sec, 400 frames by 1/10 sec, etc. This type of comprehensive data could give you high level picture and true understanding what is going on in the fluidity department.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

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I think I read somewhere on Avsim a post by someone who works for a company building proper full-motion flight simulators. I think he said that the stuff they use delivers 60fps and they won't settle for anything less.That is consistent with the impression I received on a British Airways full-motion 737 simulator last year. The graphics were very primitive, but the smoothness & fluidity were so great that overall the experience felt very convincing indeed (though I guess the full motion and the proper controls helped too, obviously!). I remember estimating that the framerate must have been 50fps or higher and I tried it out back at home on FSX by reducing all my settings and landing at simple airports etc. Sure enough, I found there was a world of difference between an approach at ~60fps and an approach at ~25fps or even ~30fps: the ground just comes towards you much more alarmingly.Tim

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-----"Sure enough, I found there was a world of difference between an approach at ~60fps and an approach at ~25fps or even ~30fps: the ground just comes towards you much more alarmingly."--------------Tim- If one has to choose between fps or a wider Field of View- I choose the latter without hesitation. For an experiment, I just took off in my triple monitor setup- 150

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