Around 19 o'clock on Sep 16, Allen Akin wrote:

> Render's gradually duplicating OpenGL functionality in ways that are
> slightly incompatible (viz the treatment of alpha-capable visuals that
> Keith and Thomas have been discussing, and the projective texturing that
> Keith and I have been discussing).

The alpha incompatibility leads from the separation of alpha values from 
the core X pixel values in OpenGL; OpenGL uses separate visuals which mark 
support for per-pixel data which is invisible through the X protocol.  I'm 
not sure how I can resolve this; perhaps OpenGL could advertise depth-32 
windows and mark them with alpha channel support so that we could draw to 
the alpha channel either through the X/Render protocols or OpenGL.

The one thing I'd like to retain is the unification of color and alpha
value that Render provides within the existing core protocol pixel values.
That may (eventually) lead us to supporting 64-bit pixels, but I think we
can do that in a compatible fashion.  Certainly increasing color depth will
be easier than increasing window coordinate space.

I also thought we'd moved Render's image transformation architecture closer
to (a subset of )that provided by OpenGL; I'm still thinking whether
mipmapping might make some kind of sense in this environment, but at least
for now I think I'll leave it out.  If there are particular filters which 
should be included in the base protocol beyond nearest and bi-linear, 
please let me know so that I can provide a spec and sample implementation.

Keith Packard        XFree86 Core Team        HP Cambridge Research Lab


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