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- Path: sparky!uunet!gatech!purdue!mentor.cc.purdue.edu!nova.cc.purdue.edu
- From: ab@nova.cc.purdue.edu (Allen B)
- Newsgroups: comp.sys.amiga.hardware
- Subject: Re: How does DCTV work ?????
- Message-ID: <55315@mentor.cc.purdue.edu>
- Date: 28 Jul 92 19:28:43 GMT
- References: <l70j6oINN6si@utkcs2.cs.utk.edu>
- Sender: news@mentor.cc.purdue.edu
- Lines: 41
-
- In article <l70j6oINN6si@utkcs2.cs.utk.edu> levi@galoob.cs.utk.edu (David Levi)
- writes:
- > Try
- > drawing a solid sphere of any color on a black background, and look at it's
- edges. You don't get well defined edges, instead you get a fade from black to
- the
- > color of the sphere. You also can't really see individual pixels.
-
- Actually the edges are remarkably sharp on the RGB
- (encoded) screen. If you were to set just one pixel, it
- would only change a few of its neighbors to the left and
- right. You can make plotting even more local, but it
- introduces some "gritty" chroma artifacts. For some
- uses, it's fine, and it's a lot faster.
-
- (You could see the effect a lot better if Digital
- Creations had used a different palette. I prefer one that
- spreads the colors out more so I can see what's going on
- better.)
-
- If you look at the screen as a lores screen (which is fairly
- accurate since the samples take two hires pixels (but
- they're staggered, so that's not completely obvious)),
- you could speak of samples. Changing one raw sample
- changes the encoding of its 6 horizontal neighbors (3 to
- each side). Smells like HAM, but it's not.
-
- This only happens with chroma information. Luminance
- info for a sample is only used in that sample. Each
- sample's 8 bits, but only 160 levels (64-223) are used for
- grayscale (you have to have a margin to add color in on top
- of that).
-
- If you could set up a DCTV Screen and then draw on it as if it
- were a HIRES 24 bit screen, you'd see some curious
- artifacts in the DCTV display (small things would be
- colored strangely or bleed), but the RGB encoding is
- pretty well localized. (Of course, since I do this every
- day, I am >not< speaking hypothetically. :-) )
-
- ab
-