Re: A89: GrayScale and Program Ideas


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Re: A89: GrayScale and Program Ideas




That is the theory, but not the practice. In reality, you have two seperate
sprites, each which are blitted to two different sections of video memory.
The interrupt routine will change the pointer to the screen displayed

.. At least this was how it was done on the TI-86. I'm sure it is done the
same way for the TI-89, for the simple fact that decoding a 2-bit/pixel
sprite would be a lot slower then having two seperate sprites which, when
two sepearate video memories are rapidly cycled at the speed from which the
ISR is called, it will look like a 4 color screen.

Ugh! I know that is a bad explanation, I have a much more detailed
explanation for grayscale in 86 central (http://www.acz.org). The same
concepts, I'm pretty sure, are for the TI-89 also.

>>Grayscales sprites simply have more bits defining the shade of each
>pixel.  In the 1-bit system commonly employed, a 0 is completely white
>and a 1 is completely black.  In a system using multiple-bits per pixel,
>00... is still white and a 11... is still black, but other values offer
>differing shades of gray.  If you wish to use two bits per pixel, 00
>would be white, 01 would be light gray, 10 would be dark gray, and 11
>would be black.  This concept continues through an infinite rang of
>possible bits-per-pixel.
>
>On Thu, 31 Dec 1998 12:20:10 -0500 "Ahmed El-Helw" <ahmed@ticalc.org>
>writes:
>>
>>Hello,
>>    I had a question - how exactly do grayscale sprites work [how are
>>they
>>made data wise].. like a normal sprite is simply .db %00010101 on the
>>z80..
>>how do you do a normal and grayscale sprite on 68k?
>>
>>    As for the program ideas -- i know I should put this on
>>ticalc.org, but
>>I have to finish alphabetisizing them first :P  Yet someone should
>>port
>>Plane Jump and Diamonds to the 89 :)  And we need high score added to
>>BoulderDash :)  As for SameGame, I still like Jimmy's better :)  Maybe
>>because it's full screen and bigger blocks?  Any thoughts?  With all
>>due
>>respect to the author - you make awesome games.. just my 2 cents worth
>>about
>>SameGame.
>>
>>Ahmed El-Helw <ahmed@ticalc.org>
>>   Program Ideas and Upcoming Programs
>>   the ticalc.org project - http://www.ticalc.org/
>>_______________________________________
>>http://hail.icestorm.com/asm/
>>ICQ: 3350394
>>
>>
>
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