Re: NSTimer causes events to be lost
Re: NSTimer causes events to be lost
- Subject: Re: NSTimer causes events to be lost
- From: Nicko van Someren <email@hidden>
- Date: Sat, 19 Mar 2005 13:43:09 +0000
On 19 Mar 2005, at 3:51, Shaun Wexler wrote:
The human eye pretty much craps out at 60fps and 25fps is TV
quality...
I take issue with that last statement. I think that the phosphors in
displays crap out, not the eye. Personally I can tell the difference
between 60 fps and 75 fps quite easily, and 100 fps looks noticeably
better to me as well. I've never seen higher than 120 fps, but at
that rate it really looks liquid. Maybe it helps to be fully
synchronized and frame-accurate as well? :-}
[Sliding badly off list-topic, though of interest to anyone who does
animation or video generation or playback...]
The human eye can see certain features of pictures up to very high
frequency and it's certainly possible for most people to tell the
difference between 80Hz and 100Hz images if the image content is of the
right sort. On the other hand the phosphor on a CRT (and the reaction
time of liquid crystal) attenuates the high temporal frequency
components that lead to flicker. Thus most of the problem with
computer animation exhibiting "jerkiness" usually comes from
inconsistent animation rate, for example when a game displays most
images for a couple of frames each but occasionally puts an image up
for one or three frames instead. There are also a whole stack of
psychological effects which mean that people notice the flicker more if
the image does not have much detail but if they are concentrating on
the detail they can happily ignore even pretty bad flicker.
For more than you ever wanted to know about this check out these two:
Budrikis, Z. (1973) Model approximations to the visual
spation-temporal sine-wave threshold data. Bell Systems Technical
Journal, vol 52(9) pages 1643-1667
Kelly, D. (1966) Frequency doubling in visual responses. Journal of
the Optical Society of America, vol 56 pages 1628-1633
or for some truly soporific bedtime reading mail me for a copy of my
PhD thesis, which has a a couple of sections on this (though the
research is a decade out of date).
Cheers,
Nicko
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