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From: dmb@wam.umd.edu (David M. Baggett)
Newsgroups: comp.sys.atari.st,comp.sys.atari.st.tech
Subject: Flicker Palettes [was Re: Graphics on the STE...]
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Date: 4 Apr 91 05:25:19 GMT
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hyc@hanauma.jpl.nasa.gov (Howard Chu) writes (in response to John Logajan):
>>My guess would be that flicker and pseudo-shadow movements would be
>>quite severe. So how does it really look?
>
>Try it and see, eh?  }-)  The color scheme I chose above gives the
>entire 256 color palette of the PC w/VGA. Try other setups....

I did try out the Fractint you posted ages ago that used flicker
palettes, and it didn't flicker too badly.  I bet some of the
combinations you'll get with the two palettes you posted are pretty
terrible though.

I've played with this technique several different times and have never
really been satisfied with the results.  I'll load up my animation
editor and try out color combinations at 60Hz -- some combinations seem
to "fuse," i.e,. blend perfectly.  In these cases you simply cannot
tell that it's swapping between two colors.  In many other cases,
however, the colors don't fuse at all, and you get horrible,
headache-inducing flicker.  Mixing 000 and 777, e.g., is totally
unbearable, at least on my monitor.  I made a little demo that just
mixed all combinations of colors in the default NEOchome palette.  I
got 256 colors on the screen.  Yup.  But you had to look at it from
across the room, with the contrast all the way down, and squinting, or
your eyes would turn to jelly and ooze out your head.  (Neither was a
pretty sight.)  :-)

I tried to come up with a formula or set of criteria that would predict
which colors would fuse and which would flicker, but never could see a
pattern.  I did notice that some combinations look OK if the "blending
area" is small, but not when you swap, e.g., two solid-color screens.
In general, the larger the area, the more flicker.  I also wonder if
it's monitor-dependent.

Anybody know how to algorithmically pick colors that always blend?
Given such an algorithm, one could write a program to find an "optimal
flicker palette" -- one where the most combinations possible were
rock-solid.  This would yield more colors on the screen at once with
little flicker and not much CPU overhead.  As Howard pointed out, such
a screen mode would be superior to Spectrum 512 because each of the N
different colors could appear anywhere on the screen.  You could
probably even do interactive animation (read: GAMES) with this mode,
although all your raster operations would be only half as fast.

Even if you couldn't find two palettes in which all combinations
blended, finding enough to get 32 solid combinations would be better
than what we've got now:  16 colors, Spectrum 512, or brain-melting
flicker.

Maybe if we assigned everyone reading this newsgroup a color combination
to try and compiled the results... (Heck, there are only 262,144 different
combinations.  Aren't there supposed to be tens of thousands reading
this group?  Well then, that's only, what, 10-20 per person?  I'll start
the ball rolling with 000 and 001...)

Dave Baggett
dmb%wam.umd.edu@uunet.uu.net