[cairo] glitz-glx

Bill Spitzak spitzak at d2.com
Mon May 24 18:29:07 PDT 2004

On Monday 24 May 2004 01:34 pm, David Reveman wrote:
> I can't see why glDrawPixels would be slower than the glTexSubImage2D.
> We can of course use glTexSubImage2D to transfer the image data to a
> temporary texture and then just draw that texture to the drawable, but
> if that's faster than using glDrawPixels, then it seems to me that the
> used OpenGL implementation is doing something kind of stupid.

I know from experience that on modern hardware glDrawPixels is usually much 
slower than anything manipulating texture maps, especially if the zoom factor 
is not 1:1.

The reason is that when they optimize these things to play Quake fast, they 
really don't care about glDrawPixels. But they do want to load textures fast.

End result is that we are changing our own software to use textures for 
everything, even for a 2D image viewing program, because it is faster.

                   ,~,~,~,~ ~ ~ ~ ~
     /\_       _|_========___         Bill Spitzak
 ~~~/\/\\~~~~~~\____________/~~~~~~~~ spitzak at d2.com

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