Xgl server

[Martijn Sipkema]

From: "David Reveman" <c99drn at cs.umu.se>
>Quoting Jon Smirl <jonsmirl at gmail.com>:
>
>> On Mon,  8 Nov 2004 21:43:55 +0100, c99drn at cs.umu.se <c99drn at cs.umu.se>
>> wrote:
>> > Cairo's glitz backend can't provide the same quality as the xlib/xcb
>> backends
>> > right now, but that should be made possible in the future, and it's of
>> course
>> > required if we'd like applications to switch to glitz when DRI is
>> available.
>> 
>> As you talking about glitz in general or glitz on opensource DRI? ATI
>> and NVidia proprietary drviers have most of OpenGL implemented while
>> DRI doesn't.
>> 
>> Why does Cairo->glitz->OpenGL have quality issues and
>> Cairo->xlib->XGL-OpenGL not have them?
>> 
>
> Glitz doesn't have any quality issues. Glitz can do trapezoids or any other type
> of geometric primitives in different ways. Cairo's glitz backend is using the
> fastest way and this doesn't produce trapezoids with anti-aliasing quality
> matching the requirements of RENDER. XGL is currently rasterizing trapezoids in
> software and then sending masks to hardware for compositing. This produces
> trapezoids with anti-aliasing quality that match RENDER. Glitz can possibly
> produce trapezoids with RENDER quality without using software rasterizing (ADD
> traps to pbuffer, pbuffer as mask to composite). This is how XGL will do
> trapezoids in the future but I'm not sure it will be much more efficient than
> software rasterizing until we get a good render-to-texture extension in OpenGL.
> Nevertheless, it will never be as fast as the way cairo's glitz backend is
> currently doing trapezoids.

Instead of using pbuffers or render-to-texture it might be an option to render
to an aux buffer using OpenGL polygon smoothing and saturate blending and then
copying to the color buffer.

Since front-to-back rendering is not always an option and is not what the
PostScript model does, using aux buffers more often seems to me the best way
to provide hardware accelerated smoothed drawing when not using multisampling.


--ms