[comp.os.msdos.programmer] Paradise VGA: Two video pages?

efricha@vortex.rti.org (Eric F. Richards) (03/06/91)

I am posting this for someone who does not have access to news:

	I have a question regarding paging using the Paradise VGA
Professional video card.

	I am trying to create two separate read/write pages so that 
I can rapidly switch between two mode 12h (640X480 16 color) images.  
This support is provided in Microsoft C 5.1 for video modes of lower
resolution by the _setvisualpage and _setactivepage functions.  I want 
to be able to write to the non-visible page and then make that page the 
visual one so it looks like the picture was drawn instantly.  This action 
would be repeated for several images to give a "motion picture" effect.

	Can this be done?  How?  Please don't skip details since
I have never tried this before.

	Please send replies to richarde@eglin.af.mil -- I'll summarize
if there is enough (or any :-)) interest.

--------
Eric Richards, Tybrin Corporation
internet: richarde@eglin.af.mil
alternate: efricha@vortex.rti.org

	Standard disclaimers apply; all flames to NUL, /dev/null, NLA0:,
or BB: (your choice...)

nyet@nntp-server.caltech.edu (prof. n liu) (03/13/91)

efricha@vortex.rti.org (Eric F. Richards) writes:


>	I have a question regarding paging using the Paradise VGA
>Professional video card.

>	I am trying to create two separate read/write pages so that 
>I can rapidly switch between two mode 12h (640X480 16 color) images.  
>This support is provided in Microsoft C 5.1 for video modes of lower
>resolution by the _setvisualpage and _setactivepage functions.  I want 
>to be able to write to the non-visible page and then make that page the 
>visual one so it looks like the picture was drawn instantly.  This action 
>would be repeated for several images to give a "motion picture" effect.

>	Can this be done?  How?  Please don't skip details since
>I have never tried this before.

>	Please send replies to richarde@eglin.af.mil -- I'll summarize
>if there is enough (or any :-)) interest.

Actually, I am interested too, since mode 12h is a standard VGA mode
This standard also sets the available pages to, guess what, 1 page.
Is there some reason why there is no support for more pages in VGA modes
for SVGA cards with adequate memory? Hell, paradise found reason not to have
a 800x600x256 mode on its 512k cards. Weird.

I take it as a sign that most games (note: animation extensive) only use
320x200x(16 or 256, two pages) or 640x400x16(EGA, two pages).

nye

respond to: nyet@cobalt.cco.caltech.edu