difference between glx and sdl opengl implementation

[Anders Storsveen]

I notice that SDL and glx rendering looks different. Its the same
difference that used to be between nvidia and 3dfx when in windows. glx
looks the way 3dfx did, with its yellow-ish graphics and sdl looks like
nvidia did, with more orange/brown colors. I have always liked the
glx/3dfx colors better, too bad the mouse is better in SDL ... :/

[Brendan Burns]

This is probably a difference between either a) the bit depth of the
SDL renderer versus the GLX renderer or b) the alpha of the renderer.
Both of these are adjustable through cvars...

--brendan

Post by Anders Storsveen
I notice that SDL and glx rendering looks different. Its the same
difference that used to be between nvidia and 3dfx when in windows.
glx looks the way 3dfx did, with its yellow-ish graphics and sdl looks
like nvidia did, with more orange/brown colors. I have always liked
the glx/3dfx colors better, too bad the mouse is better in SDL ... :/
--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 2377 bytes
Desc: not available
URL: <http://icculus.org/pipermail/quake2/attachments/20050317/a7f683e8/attachment.bin>

[Anders Storsveen]

you see it too? where and how do I set cvars? would be cool to get sdl to
look like glx.

On Fri, 18 Mar 2005 03:51:51 +0100, Brendan Burns

Post by Brendan Burns
This is probably a difference between either a) the bit depth of the
SDL renderer versus the GLX renderer or b) the alpha of the renderer.
Both of these are adjustable through cvars...
--brendan

Post by Anders Storsveen
I notice that SDL and glx rendering looks different. Its the same
difference that used to be between nvidia and 3dfx when in windows.
glx looks the way 3dfx did, with its yellow-ish graphics and sdl looks
like nvidia did, with more orange/brown colors. I have always liked
the glx/3dfx colors better, too bad the mouse is better in SDL ... :/
--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

[Anders Storsveen]

well, strangest thing just happened!
I was testing around with this to check if it affected the mouse.

SubSection "extmod"
Option "omit xfree86-dga"
EndSubSection

what I found is that, when having it like this:

SubSection "extmod"
# Option "omit xfree86-dga"
EndSubSection

the colors of glx opengl was dark and un-pretty, but when I removed the
comment again and restarted X the colors where back to "normal" the yellow
bright hue I like! Apparently xfree86-dga somehow affects the
color-rendering... Anyone have any idea why?


On Fri, 18 Mar 2005 04:13:06 +0100, Anders Storsveen <wakko at generation.no>

Post by Anders Storsveen
you see it too? where and how do I set cvars? would be cool to get sdl
to look like glx.
On Fri, 18 Mar 2005 03:51:51 +0100, Brendan Burns

Post by Brendan Burns
This is probably a difference between either a) the bit depth of the
SDL renderer versus the GLX renderer or b) the alpha of the renderer.
Both of these are adjustable through cvars...
--brendan

Post by Anders Storsveen
I notice that SDL and glx rendering looks different. Its the same
difference that used to be between nvidia and 3dfx when in windows.
glx looks the way 3dfx did, with its yellow-ish graphics and sdl looks
like nvidia did, with more orange/brown colors. I have always liked
the glx/3dfx colors better, too bad the mouse is better in SDL ... :/
--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

[Julien Langer]

Post by Anders Storsveen
well, strangest thing just happened!
I was testing around with this to check if it affected the mouse.
SubSection "extmod"
Option "omit xfree86-dga"
EndSubSection
SubSection "extmod"
# Option "omit xfree86-dga"
EndSubSection
the colors of glx opengl was dark and un-pretty, but when I removed the
comment again and restarted X the colors where back to "normal" the yellow
bright hue I like! Apparently xfree86-dga somehow affects the
color-rendering... Anyone have any idea why?

Hmm...maybe you have changed some colour settings in your xserver?
With DGA enabled (DGA stands for Directs Graphic Access) the game also
accesses your graphic hardware directly, bypassing the xserver I think.

[Anders Storsveen]

from where does sdl/glx get this information, how do you set it, and what
is it set to?


On Fri, 18 Mar 2005 19:45:43 +0100, Julien Langer <jlanger at zigweb.de>

Post by Julien Langer

Post by Anders Storsveen
well, strangest thing just happened!
I was testing around with this to check if it affected the mouse.
SubSection "extmod"
Option "omit xfree86-dga"
EndSubSection
SubSection "extmod"
# Option "omit xfree86-dga"
EndSubSection
the colors of glx opengl was dark and un-pretty, but when I removed the
comment again and restarted X the colors where back to "normal" the yellow
bright hue I like! Apparently xfree86-dga somehow affects the
color-rendering... Anyone have any idea why?

Hmm...maybe you have changed some colour settings in your xserver?
With DGA enabled (DGA stands for Directs Graphic Access) the game also
accesses your graphic hardware directly, bypassing the xserver I think.

[Anders Storsveen]

ok, guys I was playing around with nvidia-settings and I found the root of
the problem.

GLX somehow gets access to hardware gamma, while sdl does not (and uses
some software hack to make it happen). This results in much poorer
quality, while hwgamma justs ups the gamma and keeps the contrasts and
stuff the software gamma (which i call it, I have no idea what it is)
justs makes colors brighter.

I tested this while using nvidia-settings and using the gamma-slider the
following way.
When using glx and sdl in fullscreen, both at the lowest gamma setting
under the video menu they look quite similiar, however when setting both
to max they look very different, glx far superior. but when going to
windowed mode, they both look just the same again. This seems to me that
when going to fullscreen, the desktop gives up its hold over hwgamma and
glx picks it up and uses it, while sdl does not. This could be that sdl
just doesn't do it at all, or that they use different fullscreen modes or
something, that in sdl's case doesn't free up hwgamma.

Another proof that hwgamma is used on glx and not on sdl is that if you
actually set hwgamma with the nvidia-settings gamma-slider to about 1.9
which i would believe is around the max of the gamma slider in q2, the
colours, contrast and texture looks just like glx does.

I tried to peek a little into the code, but I'm not experienced enough to
make anything useful out of it, i'm also not sure what files to look in.
This could be a very simple problem to fix, so it would be great if
someone could look into it because hwgamma is FAR better than software
gamma. Also, I personally can't use glx because of the buggy mouse
(acceleration and negative movment when moving slow).

On Sun, 20 Mar 2005 04:12:29 +0100, Anders Storsveen <wakko at generation.no>

Post by Anders Storsveen
from where does sdl/glx get this information, how do you set it, and
what is it set to?
On Fri, 18 Mar 2005 19:45:43 +0100, Julien Langer <jlanger at zigweb.de>

Post by Julien Langer

Post by Anders Storsveen
well, strangest thing just happened!
I was testing around with this to check if it affected the mouse.
SubSection "extmod"
Option "omit xfree86-dga"
EndSubSection
SubSection "extmod"
# Option "omit xfree86-dga"
EndSubSection
the colors of glx opengl was dark and un-pretty, but when I removed the
comment again and restarted X the colors where back to "normal" the yellow
bright hue I like! Apparently xfree86-dga somehow affects the
color-rendering... Anyone have any idea why?

Hmm...maybe you have changed some colour settings in your xserver?
With DGA enabled (DGA stands for Directs Graphic Access) the game also
accesses your graphic hardware directly, bypassing the xserver I think.

[Anders Storsveen]

I've been doing a little investigation and I have figured out that the glx
implementation uses some kind of hwgamma (the one I can set through
nvidia-settings), and sdl uses some sort of hack. The hwgamma version
changes instantly when chaning the slider in the video setting, and it
just changes the gamma (which results in a little more yellowish but still
crisp picture), the sdl implementation is some sort of hack like in
brightness so it washes out hte colors and contrasts. If you set an
insanly high brightness value in sdl you will have no texture at all, just
colors.

however I also did the same thing in windowed mode, and then both seemed
to use hwgamma, colors and texture of both sdl and glx were similiar. So
it seems that the SDL implementation has a problem getting the hwgamma
control in fullscreen. I've tried looking into the code, and I think I
found the code which handles it, but couldn't figure it out.

would be great with sdl with hwgamma, since I think glx looks best, but
has a broken mouse for me.

On Fri, 18 Mar 2005 03:51:51 +0100, Brendan Burns

Post by Brendan Burns
This is probably a difference between either a) the bit depth of the
SDL renderer versus the GLX renderer or b) the alpha of the renderer.
Both of these are adjustable through cvars...
--brendan

Post by Anders Storsveen
I notice that SDL and glx rendering looks different. Its the same
difference that used to be between nvidia and 3dfx when in windows.
glx looks the way 3dfx did, with its yellow-ish graphics and sdl looks
like nvidia did, with more orange/brown colors. I have always liked
the glx/3dfx colors better, too bad the mouse is better in SDL ... :/
--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

[Brendan Burns]

Yeah, I should look at how the gamma stuff is done in SDL. I suspect
that SDL makes it impossible for q2 to set the gamma directly, but I'll
see...

--brendan

Post by Anders Storsveen
I've been doing a little investigation and I have figured out that the
glx implementation uses some kind of hwgamma (the one I can set
through nvidia-settings), and sdl uses some sort of hack. The hwgamma
version changes instantly when chaning the slider in the video
setting, and it just changes the gamma (which results in a little more
yellowish but still crisp picture), the sdl implementation is some
sort of hack like in brightness so it washes out hte colors and
contrasts. If you set an insanly high brightness value in sdl you will
have no texture at all, just colors.
however I also did the same thing in windowed mode, and then both
seemed to use hwgamma, colors and texture of both sdl and glx were
similiar. So it seems that the SDL implementation has a problem
getting the hwgamma control in fullscreen. I've tried looking into the
code, and I think I found the code which handles it, but couldn't
figure it out.
would be great with sdl with hwgamma, since I think glx looks best,
but has a broken mouse for me.
On Fri, 18 Mar 2005 03:51:51 +0100, Brendan Burns

Post by Brendan Burns
This is probably a difference between either a) the bit depth of the
SDL renderer versus the GLX renderer or b) the alpha of the renderer.
Both of these are adjustable through cvars...
--brendan

Post by Anders Storsveen
I notice that SDL and glx rendering looks different. Its the same
difference that used to be between nvidia and 3dfx when in windows.
glx looks the way 3dfx did, with its yellow-ish graphics and sdl looks
like nvidia did, with more orange/brown colors. I have always liked
the glx/3dfx colors better, too bad the mouse is better in SDL ... :/
--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

--
Anders Storsveen
The Next Generation
http://www.generation.no

[Nick Warne]

Post by Anders Storsveen
I notice that SDL and glx rendering looks different. Its the same
difference that used to be between nvidia and 3dfx when in windows. glx
looks the way 3dfx did, with its yellow-ish graphics and sdl looks like
nvidia did, with more orange/brown colors. I have always liked the
glx/3dfx colors better, too bad the mouse is better in SDL ... :/

Yes. I remember around 1999 when I bought my first 3DFX card - I was terribly
disappointed how the graphics changed from looking 'gothic' like crispness to
sort of like browny-orange (and very, very dark).

But since then, I got used to it, but still need to adjust gamma using SDL to
be able to see a damn thing. Still, the best for Linux Quake2, I feel.

Nick