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 [cjwat...@ubuntu.com] -- technical-board mailing list technical-board@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/technical-board
