RE: [Algorithms] DXTC encoder?

[Tom F. <tom...@ee...>]

Agreed - those green/purple lightmaps look somewhere the opposite of
wonderful. One thing you can do is not use the extra bit of green, so =
you do
get 555 encoding - all you need to do is make the shader multiply by =
(1,2,1)
(or (0.5,1,0.5) with a mod2x for PS1.x).

Of course, being lightmaps, they are magnified, so on NV25 that =
"somewhere
close to 787" really isn't - it's very very obviously stippled 555, and =
the
stipples are about a metre across in places (depends on lightmap
resolution). We ended up just using DXT3 - you can often pack a =
greyscale
texture in the alpha channel (e.g. specular) and then you don't even =
lose
the memory.

TomF.


> -----Original Message-----
> From: gda...@li...=20
> [mailto:gda...@li...] On=20
> Behalf Of Jon Watte
> Sent: 16 February 2005 18:02
> To: gda...@li...
> Subject: RE: [Algorithms] DXTC encoder?
>=20
>=20
>=20
> > Really?  The extra green bit is just dropped?  Or randomly=20
> rounded up or=20
> > down?  Arg!
>=20
> That doesn't matter -- or could even be good. With 565, there is no=20
> way to represent pure gray; you get that wonderful green/purple=20
> banding on lightmaps and other washes :-(
>=20
> I would have been happier if DXT/S3TC had been defined as a 555=20
> format, for this very reason. Maybe those extra two bits out of the=20
> palette could have been used for something else, too...
>=20
> Cheers,
>=20
> 			/ h+
>=20
>=20
>=20
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