composite manager thoughts

[Jon Smirl]

You don't really want a pixel or vertex shader to do this. What you need is a
texture program. Some hardware allows compressed textures, I wonder if that is
done in microcode? If so it might be possible to write a texture program. A
glyph would just a be represented by as a very special compression algorithm.

Maybe an expert on shaders will read this tomorrow and answer all our questions.


--- Allen Akin <akin@pobox.com> wrote:
> On Sun, Dec 28, 2003 at 07:53:12PM -0800, Jon Smirl wrote:
> 
> | This is why I've been sending some proposals around to people about drawing
> | text with pixel shaders. The basic idea is to have one shader per glyph.
> 
> I'm told that context switching the shaders is very expensive on current
> hardware, so that would be important to test.  (You might be forced to
> optimize by drawing all the "a" characters on a page, then all the "b"
> characters, etc.)
> 
> | TrueType glyphs would be preprocessed into curve segments and each pixel
> would
> | be tested if it is inside or outside the segments. ...
> 
> What's the advantage over using vertex programs to generate triangles that the
> rasterizers then handle?
> 
> Also, since the curve segments change under geometric transforms like
> projective mapping, would one fragment program be enough, or would you need
> different programs to handle different sorts of transformations?
> 
> |                                             ...  It is possible to
> antialias,
> | subpixel render, hint at small sizes, etc in the shader program.
> 
> I don't know enough about hinting, but as far as I can tell several of the
> algorithms require knowledge about adjacent structures at higher levels of
> abstraction than individual pixels -- particularly edge widths, angles,
> dropouts, etc.  It seems to me that it would be hard to give a fragment
> program
> enough context to handle that sort of thing.  What are your thoughts on
> that?
> 
> | So far as I know no one has actually tried writing a shader that draws text.
> 
> Not that I know of, either.  But I suspect it's been done, and we just
> haven't heard.
> 
> Allen
> 
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=====
Jon Smirl
jonsmirl@yahoo.com

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