Re: ancient animation

[rubywand@aol.com (RUBYWAND)]

In article <4nanqp$gjo@gap.cco.caltech.edu>, nathan@cco.caltech.edu
(Nathan Mates) writes:

>
>   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. ....
>

     The leftmost line is clearly smoother. Based upon the slope of the
line, this could not happen unless at least the edge dots were offset
about 0.5 pixel. Neat!


Rubywand