[cairo] anti-aliasing quality in glitz/OpenGL vs. Cairo native rasterization?

Leon Woestenberg leonw at mailcan.com
Thu Jun 10 15:43:30 PDT 2004


David wrote,
On Fri, 2004-04-30 at 21:04 +0200, claude M wrote:
 >> i've tested Cairo+Glitz. Glitz selects the Multisample extension to
 >> perform antialiasing if it finds it. What i can say is that it worked

 > Yes thats right, glitz uses the multi-sample extension. Glitz's format
 > system allows you control anti-aliasing. You can select if you like to
 > use AA or not and number of samples used for multi-sampling.

I am just dropping in this mailing list (and sorry for not being able to
reply properly, I copied the above from the archive).

How does the OpenGL output compare against the Cairo software rasterizer?

 From what I understand Cairo estimates pixel coverage very accurately, 
allowing to exploit the full range of (pixel color) quantization levels.

Contrary to this, a hardware video card will do super- then subsampling
to have 4 quantization levels for anti-aliasing in 2x2 supersampling,
or 16 in 4x4 mode. (I know of no higher level supersampling in currently
available cards).

Is my assumption true that the typical OpenGL backend output is worse
than native rasterization in the Cairo software quality-wise?

I may start a thesis project exploiting offloading parts of a rasterizer
into logic (as GPL VHDL code) and Cairo may be an interesting candidate


Leon Woestenberg.

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