Re: The big divide - graphics contexts and window servers

[Philippe C.D. Robert]

On Tue, 19 Mar 2002, Jeff Teunissen wrote:
> > What do you mean by 2D stuff exactly? Could you give an example maybe?
> > 
> > My guess is that 2D does not exist at all, there is no special path for
> > 2D rendering in commodity drivers. Thus 2D is as slow or fast as 3D. But
> > of course this is just a guess, I did not looked at sources to proof it.
> 
> I'll give a simple example.
> 
> Say I have two quads on the screen, one taking up the whole screen (the
> background) and another in front of it (the window). The background has alpha
> 1.0, the window has alpha 0.7. Both are textured; the background has a typical
> desktop image on it, and the window has a texture containing text on it.
> In some systems, the window will look like it has 1.0 alpha and will keep
> doing that unless alpha goes below 0.5, at which point it disappears. In
> others, it will actually work, but it'll be very slow. If I add some
> transformation to the window so that it is no longer billboarded, the speed
> comes back.

Uhm, do you call that 2D path? I'd rather call it a bug...:-) I say so 
because to me this seems to be a normal blending operation. Since this is 
fragment processing and is done at the very end of the GL pipeline it cannot
depend on the dimension of the geometry...  I probably miss sth here, though.

BTW what GL implementations and cards did you use for testing? I am just 
curious...:-)

> "Commodity drivers" includes a LOT of stuff, including the old 3Dfx Voodoo
> cards, which eventually did get a passable GL (as opposed to their MiniGL). It
> was never good, though.

Yup, but for GNUstep we could say that we only support NVidia and Mesa which 
seem to be working more or less as expected. MiniGL isn't used in these days 
anyway, I guess. It is still worth a try. We could even use xgps as fallback
option.

-Phil
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