Re: A83: Greyscale Help

[Prev][Next][Index][Thread]

Re: A83: Greyscale Help


In a message dated 6/12/00 1:47:17 AM Central Daylight Time, 
gte172i@prism.gatech.edu writes:

> i'd like to reply "Look Harder", but i am a nice guy.
>  
>  this information is readily available on www.ticalc.org
>  search for "grayscale"
>  or look in 82,83,85,86 asm / misc or graphics directories for grayscale.
>  
>  
>  to answer your question, grayscale is best accomplished by maintaing
>  multiple graph buffers and displaying them on top of each other in a timed
>  pattern that is done by the interrupts.  for four level grayscale, 4
>  colors, you would have 2 buffers, the graph_buffer and the apd_buffer, and
>  you would display one buffer, wait a few interrupts, then display the next
>  buffer on top of the previous, then you would clear the graph buffer and
>  do it over again.
>  
>  -harper

I'd like to note that Dan Englender and I have exhausted our efforts in 
trying to "discover" flickerless grayscale for the 82/83/83+ series during 
this past week. We certainly found out that the LCD Driver can handle the 
manual updating of the two buffers to the screen, and it turned out to be 
flickerless, yet there was some inconsistency with the timing that we beleive 
to be a hardware issue, not something we can control well enough through 
software. This was to be built into MirageOS, and it worked alright on 83 
plus calcs that were made in 02/99 and earlier, but during 03/99 and later, 
TI seemed to have changed the hardware and those calcs do not display the 
same results that we would have liked. So our efforts have been futile and  
nothing stable enough could be acheived. I'll see if we can post the demo we 
made that works under ION, but it should show that a Grayscale engine is just 
not practical from a visual point of view. It is still possible that programs 
could do manual grayscale in small quantities, which involve constantly 
XORing a sprite or swapping sprite pictures, and I beleive that would be fast 
enough and look good. Other than that, I have given up on the task.=P 
...Perhaps back to the subject now of where to find information on grayscale, 
the GrayDemo by Bill Nagel and the Chameleon program by Shawn Lindberg are 
good places to look, they include their sources and somewhat of developer's 
information. Hmm, maybe I should mention I dont want to discourage anyone 
else from using a grayscale engine, or perhaps trying to experiment and 
"invent" flickerless grayscale. Go for it... :)

Jason_K
Follow-Ups: