Persistence of vision?

I'll start with a quote (not from me) which explains my question

"Persistence of vision works because the human eye and brain can only process 10 to 12 separate images per second, retaining an image for up to a fifteenth of a second. If a subsequent image replaces it in this period of time it will create the illusion of continuity."

If this is the case, why are we so concerned with getting the extreme FPS performance figures often quoted here. My aging memory tells me that at one time 27 FPS was the desirable target and anything above that was waste of time and money.

Why is it so?

Peter

I agree with that quote entirely. In am always amused by the flightsim community who often go to extremes to get frame rates up to, and over 100fps. Anything above 30fps is really undetectable to the average human eye, but the fps enthusiasts will disagree and rave about the increased clarity etc. Personally, the major factor to how good your Trainz looks is your own vision, (eye health).

There is a vast difference between "persistence of vision" and how many fps the human eye can detect - the two are totally different effects.

Tests have shown that the human eye and brain can detect events as fast as 1 millisecond apart - that is 1000fps.

Test have also shown that your eye (and brain) can easily detect flickering in monitors at 240fps.

Some sources to consult.

https://www.quora.com/What-is-the-h...o-we-essentially-stop-noticing-the-difference


https://us.battle.net/forums/en/overwatch/topic/20749876977

From personnel experience I can say that 30 looks decent, 60 is good, anything above 60 is more of a "TADAAAAAAA!" but in-between 30 and 60, I find that my brain seems to lose frames? if that makes sense? It just looks a little choppy. As far as I know the brain likes multiples of 30FPS for processing still image's into moving pictures, but above 60 the difference is hard to see.

Then again this is coming from a person who dislikes HD TV's so :hehe:

The thing about framerates isn't how many you can pump out of a game, but rather, how consistent the framerate can be.

Something i hold true with games is that a low yet consistent 20FPS looks miles better than a choppy, inconsistent 30-60FPS. It's more about consistency than it is getting as many FPS as possible out of a game, i believe.

Answer #3 is the closest to reality. Today it will be hard to verify this. But in PAL or NTSC times, you live in USA and one day you go to Europe. First think you notice when looking at a TV, is the flickering 29.99 flames/second versus 25 fps in Europe. That was because your brain is "trained " for "smooth" 30 fps and will detect the lower frame rate, meanwhile an European does not know what you are talking about (same for fluorescent light tubes). Now you look at 30 Fps motion image and it looks good if the image is static or slowly moving. But if it moves fast, and you could freeze a frame, you will see the blur. If you run at 60 or 120 Fps, that frame may show more detail. Somehow the brain may see this, perhaps as a psychological effect, but nevertheless is there. You want it more complicated? Those 25 or 30 Fps were interlaced. Meaning that half would be drawn and another half right after. Today we use progressive scanning, meaning that the full frame is draw in one shot, from top to bottom. To the brain it does not matter, but imagine the amount of electronics needed to accomplish this and how fast things have to be.

I suggest there is another factor to consider. Trainz animation is based on 30FPS so at 60FPS you are getting two shots of the same frame, wouldn't this seem to infer that the action appears to be slowed down as each frame is seen for two seconds not one.

What in a typical map view has that same rate of change. Can the Trainz engine produce a display where the actual frame changes occur at the higher rate. Even if the human eye has the capability of seeing higher change rates, where in Trainz do images change at this higher rate.

Does this set 30FPS value get multiplied by the higher FPS capability of the computer?

There is an instance where Trainz/T:ane (whatever) can't keep up with the frame rate. Watch the spoked driving wheels on a steam locomotive, as the speed increases the wheel animation appears to slow and then reverse. This does seem to show that Trainz does have limits on the actual rate of the images it can display.

I'm not trying to argue against the search for higher frame rates but it does seem to be unnecessary and may cause new members to believe that expenditure is required that could put them off the hobby. Anyway it is an interesting subject.

Thanks for reading and thinking.

Peter

Interesting to note that traditional movies were always shot and projected (in the cinemas) at 24fps. Peter Jackson, in his Hobbit movies, broke that tradition by shooting on digital at 48fps. At the time there was a lot of argument about what difference, if any, this made - "The Hobbitt" received mixed reviews with some criticism directed at the new frame rate.

Since then more digital movies have made the switch to 48fps and even higher rates (up to 120fps).

pware said:

Interesting to note that traditional movies were always shot and projected (in the cinemas) at 24fps. Peter Jackson, in his Hobbit movies, broke that tradition by shooting on digital at 48fps. At the time there was a lot of argument about what difference, if any, this made - "The Hobbitt" received mixed reviews with some criticism directed at the new frame rate.

Since then more digital movies have made the switch to 48fps and even higher rates (up to 120fps).

Click to expand...

Go back to what I said about the flickering on TV, Europe versus USA 25-30 frames per second. This effect is most noticeable depending on what part of the eye you are concentrating. Look at the image directly and the flicker is less, but on peripheral vision, the flicker is very noticeable. Now, go to a movie theater and look at the vary large rectangular panoramic screen. Your eye is focus on the central part where the action takes place, and the sides of your eyes "see" the extremes, and there, at 24 FPS, the flickering shows. So, engineers decided to up frame rates so there would not be any flicker, center or borders of the screen. Related to Trainz, I think 30Fps second is sufficient, but today most of the monitors a capable of at least 60 (called refresh rate), 60 is more than enough for practicality.

The comments about higher frame rates are interesting but they relate to the display of an existing image projected to a screen. I believe that Trainz is a different case, what we are seeing is a 'constructed' image so perhaps the pertinent value is 'screen refresh rate' and would be controlled by the electronics of the PC, the monitor and the Trainz code itself. Which of those three is the limiting factor? Just a thought, if the cinema screen was only visible at 30 times per second the increased rate would have no effect

Why did Auran choose 30FPS as the controlling value for animation, was it because the underlying code could only handle that rate?

This may be muddled thinking but consider this. Think of the spoked wheel again, if it is crossing the screen at 30mph, that means the top of the wheel is traveling forward at 60mph and the bottom is stationary. As speed increases you will see a Doppler effect beginning with the spokes at the top and spreading around the wheel. What you actually see also depends on the number of spokes. Does the Doppler result from the FPS rate or the capacity of Trainz to refresh the image at the required rate?

We normally sit fairly close to the monitor, does peripheral vision play any part in what we are seeing. I can spread my arms right out to either side and my hands are visible both sides 180 degrees apart while I remain focused on the screen. Peripheral vision plays no part in what I am viewing.

Interesting discussion.

Peter

narrowgauge said:

I suggest there is another factor to consider. Trainz animation is based on 30FPS ...

Peter

Click to expand...

Where is it written that Trainz is based on 30 FPS? We can cap the max refresh rate which just prevents wild swings in the FPS. Probably a factor in the steady view.

Some quick thoughts:

* Most people can see up to around 60fps motion in their center vision and around 80fps motion in their peripheral vision.
* Beyond that, the frames will blur together, effectively producing (in your optic system) a form of motion blur. This isn't a bad thing but isn't very relevant in most cases.
* Some gamers prefer crazy-high refresh rates, but this typically has more to do with reduced input latency than anything to do with the visual system.
* Lower frame rates look acceptable with sufficient motion blur and carefully controlled camera movement. Without motion blur, low frame rates tend to look choppy. With heavy camera rotation, low-framerate motion blur can be quite sickening. This works out well for TV and movies because the technology provides motion blur and the camera movement is carefully controlled by the content producer.
* Uneven frame rates are bad, doubly so when the camera is moving very steadily and when the frame rate is otherwise high. This introduces very noticeable micro-stutters due to mis-prediction of frame output time. G-sync (and similar technologies) can help avoid this. You can get a better result with an even 30fps than you can with an uneven near-60fps.
* Trainz itself doesn't have any magic numbers when it comes to frame rates (at least not within the range of frame rates that we're taking about for display on a normal monitor).

chris

Martin.

I wrote that Trainz animation is required to be based on 30FPS, and I wondered whether this indicates that the basic program may have the same constraint.

This all started because I read here about frame rates more than double this 30FPS and wondered whether this is really required for the average person with average cash resources who might be biased against Trainz for this reason. As to whether it is important, that is literally 'in the eye of the beholder and the depth of their pockets'

Edit:- Chris posted this while I was writing
" Trainz itself doesn't have any magic numbers when it comes to frame rates (at least not within the range of frame rates that we're taking about for display on a normal monitor)". It answers my question

Peter

narrowgauge said:

I wrote that Trainz animation is required to be based on 30FPS, and I wondered whether this indicates that the basic program may have the same constraint.

Click to expand...

Regarding this:

* Trainz doesn't really care what frame rate you use. As long as your animation frame rate is configured correctly in the FBX file, all will be happy.
* Even if your animation is keyframed at 30fps, Trainz will interpolate between those frames to provide results at whatever display frequency your hardware can handle.

chris

Extremely interesting discussion. I run Trainz at 30fps for steadiness, which seems sufficient - though the monitor is 60fps native. But what intrigues me is this: How is the CGI in a film handled? I assume the sequence is already rendered and then inserted into the visual stream during editing. But at what rate are CGIs rendered? Would it be the same as the film or would it need to be faster?

I ask this question because it seems to be to bear some relevance to what has been said above about apparent visual streaming at, say, 26/30frames, while the images are being rendered at possibly much higher rates.

If you are talking about traditional film, where the digital CGI sequence is imprinted onto film, then it would be rendered and imaged at the same rate as the film - 24fps.

Some traditional films have used advanced CGI morphing effects to produce some spectacular slow motion explosion effects. "Swordfish" is one that comes to mind where explosion effects were filmed at a much higher fps rate and then CGI experts went to work to interlace additional frames between the filmed frames to reduce any "jerkiness" and improve the "smoothness" of the motion. The high speed and additional CGI frames were then spliced into the film to be shown at 24fps but because each second of the special effects action actually took many more frames than the normal 24 (I cannot recall the exact number) then every second of real time action became several seconds of very smooth slow motion action - it did look impressive.

A similar effect was used in the opening credits of Deadpool 1 - but that was shot entirely in digital.

Higher fps rates are often used to reduce motion blur and action "stutter", particularly as others have stated above, when the camera pans across a scene.

As for digital movies, which are now almost universal, I am uncertain but I would suspect that the entire movie, including CGI effects, would be rendered and shown at the one set speed.

pware said:

If you are talking about traditional film, where the digital CGI sequence is imprinted onto film, then it would be rendered and imaged at the same rate as the film - 24fps.

Some traditional films have used advanced CGI morphing effects to produce some spectacular slow motion explosion effects. "Swordfish" is one that comes to mind where explosion effects were filmed at a much higher fps rate and then CGI experts went to work to interlace additional frames between the filmed frames to reduce any "jerkiness" and improve the "smoothness" of the motion. The high speed and additional CGI frames were then spliced into the film to be shown at 24fps but because each second of the special effects action actually took many more frames than the normal 24 (I cannot recall the exact number) then every second of real time action became several seconds of very smooth slow motion action - it did look impressive.

A similar effect was used in the opening credits of Deadpool 1 - but that was shot entirely in digital.

Higher fps rates are often used to reduce motion blur and action "stutter", particularly as others have stated above, when the camera pans across a scene.

As for digital movies, which are now almost universal, I am uncertain but I would suspect that the entire movie, including CGI effects, would be rendered and shown at the one set speed.

Click to expand...

Thanks for details. I had assumed that the "real" footage even in modern films was shot analogue, which seems not to be the case. So the point I raised is irrelevant here. That said, the ability of modern professional digital cameras to handle light/contrast is very impressive, especially when tracking mobile scenes. I suppose my view of digital footage was influenced by the likes of David Lynch's excesses. Even so, I wonder if a digital camera could replicate the candlelit shots achieved by Kubrick in Barry Lyndon, apparently using a NASA low-light lens.

phimat said:

I wonder if a digital camera could replicate the candlelit shots achieved by Kubrick in Barry Lyndon, apparently using a NASA low-light lens.

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I suspect that we've reached the point where professional digital cameras will beat traditional analog cameras at pretty much anything you'd like to throw at them. Obviously you're not going to compare a phone camera straight across with professional kit. Optics still matter, and the skill of the artist still matters

chris

WindWalkr said:

I suspect that we've reached the point where professional digital cameras will beat traditional analog cameras at pretty much anything you'd like to throw at them. Obviously you're not going to compare a phone camera straight across with professional kit. Optics still matter, and the skill of the artist still matters

chris

Click to expand...

To the extent that we all swim in a digital sea now, I agree. But I still remember my response to that Kubrick gambling scene and the sheer magic of how the light merged into the darkness. Of course that was an analogue event, but there is still something of that effect in the digital remaster. I have shot digital (Canon 5D, still the largest pixels available) for over ten years and I am still aware of shots where I know we still do not have the digital colour to do full justice to what I see. (By contrast, my brother never could accept digital; just hordes his slides now.)

phimat said:

(By contrast, my brother never could accept digital; just hordes his slides now.)

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Unfortunately, the colours in those analogue slides will fade with time. Digital data can be copied with 100% fidelity and, as long as the media is kept up to date, will last "forever"(TM).

But yes, there is an "atmosphere" to analogue images that current digital technology finds hard to replicate.