Re: ancient animation

[nathan@cco.caltech.edu (Nathan Mates)]

In article <4n6gpm$o0u@newsbf02.news.aol.com>,
RUBYWAND <rubywand@aol.com> wrote:
>In article <31963D91.41C67EA6@math.ubc.ca>, Michael Kennett
><kennett@math.ubc.ca> writes:
>>Anyway, Bob Bishop's Apple Vision used the 2 different white colours
>>of the hires mode to achieve a resolution of 560x192. I was very
>>impressed with this trick - I had small successes in recreating it
>>with a few of my own programs.

>     Applevision is a cute demo. It does not appear to be in 560 x192
>resolution. Although 280 pixels are available per horizontal scan line,
>the rules for dot pairing produce somewhat lower color "resolution". A
>guess is that the notable achievement of Applevision is animating a figure
>in something like true 280 x 192 resolution on a color monitor.

   Despite single hires being 280x192, and color resolution something
like 140x192, the way things were done on the Apple II meant that
there were two ways of drawing "white." Further, these two were
slightly offset from each other, giving a doubled horizontal
resolution for only whites on separate lines, etc.

   Someone a while back had a program which demonstrated it; with about
two minutes playing around on my GS, here's one that does the same:

10 HGR: FOR I=1 to 40: FOR J=0 TO 1
20 HCOLOR=3+4*J:HPLOT I+1,I+I+J:HPLOT I+2,I+I+J
30 HCOLOR=3:HPLOT I+20,I+I+J:HPLOT I+21,I+I+J
40 HCOLOR=3:HPLOT I+J+40,I+I+J:HPLOT I+J+41,I+I+J
50 HCOLOR=7:HPLOT I+60,I+I+J:HPLOT I+61,I+I+J
60 HCOLOR=7:HPLOT I+J+80,I+I+J:HPLOT I+J+81,I+I+J
70 NEXT:NEXT

   Run it on a real Apple II. It puts 5 diagonal lines on the screen,
The leftmost looks far better than the others; it uses the differing
whites. The others look far more stair-steppy. I did two of the
other sort to show how things would look with and without extra
horizontal offsets in the HPLOTs; no effective difference. Same thing
with using only color 7 in lines 50 & 60.

Nathan Mates
-- 
<*> Nathan Mates http://www.ugcs.caltech.edu/~nathan/      <*>
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