Re: XFree resolution & window rendering

[Steve Baker <sjbaker1@airmail.net>]

Felix Kollmann wrote:
> 
> Hi,
> 
> does anybody know how to get and set the resolution of XFree?

Dunno.

> And can anybody say if window rendering is possible with a 3Dfx card. I
> thought I heard something in this directon.

Depends on the 3Dfx card:

  Rush    -- Yes.
  Banshee -- Yes.
  Voodoo3 -- Yes.
  Voodoo1 -- Well, kinda.
  Voodoo2 -- Well, kinda.

The Voodoo-1 and 2 are technically unable to render into a window
because they don't have hardware to do that. These cards are
completely separate from your 2D SVGA card and they are not
known to Xfree at all.

However, Mesa has a hack that renders the image using the Voodoo1/2
card, then copies the data out of the Voodoo's frame buffer, and
into the SVGA card using the CPU.  This is very slow for applications
like games - and will generally cut your speedy 60Hz frame rate to 
maybe 10Hz.

The degree of slowdown is dependent on the size of the window,
how well the pixel format of the SVGA display matches the 16 bit
video format of the Voodoo card - and on the speed of your CPU
and SVGA card.

However, this slowdown doesn't make it useless - if you had some
kind of scientific visualisation application that runs at one
frame every minute in software-only OpenGL, and one frame per
second in hardware...the additional ~1/10th second it takes to
blit the image into the SVGA card is still well worth-while.

To do this using Mesa, set the shell variable "MESA_GLX_FX" to
"windowed" rather than the usual "fullscreen".  There is also
a function provided in Mesa to switch between windowed and
fullscreen in software.  It's mentioned in the README.3dfx
that comes with Mesa.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjbaker1@airmail.net (home)  http://www.woodsoup.org/~sbaker
sjbaker@hti.com      (work)