Patent enquiry - mesa floating point buffer support

[Colin Watson]

On Fri, Jul 08, 2011 at 05:28:18PM +1000, Christopher James Halse Rogers wrote:
> I'd like to enable mesa's floating point buffer support in the Ubuntu
> packages (accomplished with the --enable-texture-float configure
> option).  This allows mesa to provide additional functionality in the
> form of the GL_ARB_texture_float¹ and ARB_color_buffer_float² GL
> extensions.
> 
> These are obviously not widely used in Ubuntu currently.  As far as I'm
> aware, the most common user would be Wine, as DirectX provides
> equivalent functionality.
> 
> The patent in question is linked to from the GL extension
> specifications, or can be found at ³.  It's not clear to me whether or
> not enabling this code would actually infringe, as it seems that a
> hardware rasterisation circuit is integral to the claims.  Mesa upstream
> has been cautious with implementing this support due to this patent,
> however.
> 
> [1]: http://www.opengl.org/registry/specs/ARB/texture_float.txt
> [2]: http://www.opengl.org/registry/specs/ARB/color_buffer_float.txt
> [3]:
> http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=6,650,327.PN.&OS=PN/6,650,327&RS=PN/6,650,327

Hmm.

I can confirm that we have received no other communication about this
(but we wouldn't expect to have done, since it isn't currently enabled
in Ubuntu).

It is true that many claims of this patent are specific to hardware
circuits.  However, claims 9 to 24 do not specify the presence of any
particular circuitry, and my reading of them is that they would cover
software implementations.  I am not sufficiently fluent in the language
of OpenGL specifications to be able to tell whether those claims cover
the two extensions in question, but they seem quite extensive.
Unfortunately, in jurisdictions permitting software patents, I don't
think that we can rely on the defence that these claims only cover
hardware, unless you or a relevant expert can confirm that Mesa is only
affected by the hardware-specific claims.

The language in the "IP Status" sections of the OpenGL specifications is
quite aggressive and explicit: "SGI will not grant the ARB royalty-free
use of this IP for use in OpenGL, but will discuss licensing on RAND
terms, on an individual basis with companies wishing to use this IP in
the context of conformant OpenGL implementations. SGI does not plan to
make any special exemption for open source implementations."

It would be interesting to know whether this patent is being actively
enforced.  However, given that it's referenced from the specifications,
and given Mesa upstream's reticence, we might have a hard time arguing
that we were unaware of it.

What practical functionality do we lose out on by not having these GL
extensions?

I am neither a lawyer nor an OpenGL expert.

Regards,

-- 
Colin Watson                                       [cjwatson at ubuntu.com]