Fixed point matrix representation considered harmful

Keith Whitwell keith at
Thu Mar 20 13:23:27 PDT 2008

> > > > Exception values (NaN, +/-inf) should be invalid, but denorms shouldn't
> > > > cause any issues for us.
> > > 
> > > Except that it complicates decoding for non-IEEE platforms. Think VAX.
> > 
> > Are we actually designing for VAX these days? There aren't many other
> > non-IEEE platforms that I know of: even lame embedded/consumer chips are
> > pretty much all IEEE now, TTBOMK.
> Well, at least some of the RISC platforms have IEEE-like floating point,
> but don't do the magic values. Think about Alpha. My point is to just
> specify a simple binary format and leave out all the special magic
> values.

Maybe the thing to do is to figure out what rules there are for encoding floats in GLX and apply the same rules to render.  Then at least you get the same problems & solutions for this as have existed all along with GLX & if there is code to handle it, you can reuse it.

After all indirect GL apps have been sending floating point matrices to X servers for the last... 15 years?  


More information about the xorg mailing list