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From: rjc@geech.gnu.ai.mit.edu (Ray Cromwell)
Subject: Re: NeXT/Amiga Flamage: Get a life.
Message-ID: <1991Apr10.035203.3854@mintaka.lcs.mit.edu>
Sender: news@mintaka.lcs.mit.edu
Organization: The Internet
References: <10902@uwm.edu> <&5aGlabl1@cs.psu.edu> <1991Apr10.005729.22997@cunixf.cc.columbia.edu>
Date: Wed, 10 Apr 91 03:52:03 GMT
Lines: 57

In article <1991Apr10.005729.22997@cunixf.cc.columbia.edu> es1@cunixb.cc.columbia.edu (Ethan Solomita) writes:
>In article <&5aGlabl1@cs.psu.edu> melling@cs.psu.edu (Michael D Mellinger) writes:
>>
>>In article <10902@uwm.edu> gblock@csd4.csd.uwm.edu (Gregory R Block) writes:
>>
>>
>>   Yes, which is only usable on the CUBE, which is about 8000 dollars, or more...
>>
>>Of course.  I was just correcting an incorrect statement made by an Amiga user.
>>
>>   The 12 bit color with 4 alpha channel is the color slab, a likewise joke.
>>
>>Hey, 4096 colors looks pretty impressive :-).
>>And on a million pixel display, to boot.
>>
>>-Mike
>
>	I must be missing something here. The 040 is about three
>times faster than the 030, right? And the color NeXT is 12 bits
>as opposed to 2 bits on the old NeXTs, or six times the bit
>planes. So, the color NeXT is twice as slow with the graphics/GUI
>as the original NeXT, right?
    Assuming the NeXT uses the CPU to do it's rendering which it probably
does unless the color NeXT's have a blitter.

>	Truthfully I don't know what an alpha channel is. Is it
>basically an overlay screen?

 From what I understand, alpha channel is transparency. I'm not used to
it in a 2d sense, but in a high end z-buffered graphics system, Alpha
channel specifies how much color to borrow from the pixel underneath.
So if you have a blue sphere behind a red sphere, an alpha channel
value of 128 (with 8 bits of alpha) specifies a 50% blending (im guessing
here. I don't know how the real implementation of alpha works). So
in theory, 50% of the color of the blue pixels would "show thru" the red's
causing the red sphere to be partially transparent.
 Pretty neat for speeding up 3d rendering without using dithering.
 I have no idea of how alpha works in a 2d system with no Z buffer.
I guess it changes into 'anti-aliasing blending' from neighboring
4x4 pixels.
  Talk aabout expensive displays. I've heard about frame buffers out there
that have 24 bits color, 8 bits alpha, 32 bits z buffering, 1 bit overlay,
2 bits of control, and even gamma correction. All this totals more than 64
bitplanes. I heard SUN even developed displays in excess of 100 bits per
pixel!

>	-- Ethan
>
>Q: How many Comp Sci majors does it take to change a lightbulb
>A: None. It's a hardware problem.


--
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|n|   rjc@albert.ai.mit.edu   Amiga, the computer for the creative mind.  |n|
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