Re: highlighting a texture

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Ran Yakir (rany++at++rtset.co.il)
Sat, 13 Feb 1999 10:18:21 +0200

Stephen,

Why don't you try the texture color scale and bias ? I think those are cheaper
than TLUT. You can then saturate your texture color, in order to highlight it,
or you can totaly remove one color component.
You control the scale and bias with glTexParameterfv, with the arguments
GL_POST_TEXTURE_FILTER_SCALE_SGIX and
GL_POST_TEXTURE_FILTER_BIAS_SGIX

Ran

Phil Keslin wrote:

> The OpenGL imaging operators will effect any pixel movement operations
> (ReadPixels, DrawPixels, CopyPixels, CopyTexSubImage, CopyTexImage,
> TexImage, etc.). They can be expensive though (depending upon the
> operation).
>
> Angus suggested the TLUT, but what about modulating the texture with a
> different color?
>
> - Phil
>
> Angus Dorbie wrote:
> >
> > It does affect your texture download path but you'd have to resend from
> > the host.
> >
> > You could use a TLUT, texture lookup table, or you could perhaps change
> > the texture environment.
> >
> > Cheers,Angus.
> >
> > Stephen Maher wrote:
> > >
> > > Hi,
> > >
> > > I'm trying to find a way to slightly change the appearance of a
> > > texture (including clip textures) on the fly to make it appear
> > > "highlighted" or "selected".
> > >
> > > I first tried modifying the GL_COLOR_MATRIX_SGI, but I guess the "imaging
> > > pipeline" that it effects, as described in the OpenGL on SGI doc, is the
> > > glDrawPixel, etc., path, not the texture mapping path.
> > >
> > > And clever ideas?
> > >
> > > Thanks,
> > > Steve
> > > --
> > > stephen.maher++at++gsfc.nasa.gov (301) 286-3368 fax:(301) 286-1776
> > > http://holodeck.gsfc.nasa.gov/vr/vr.html
> > > NASA Goddard Space Flight Center
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> >
> > --
> > "Only the mediocre are always at their best." -- Jean Giraudoux
> >
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> > http://www.dorbie.com/
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>
> --
> Phil Keslin <philk++at++engr.sgi.com>
> =======================================================================
> List Archives, FAQ, FTP: http://www.sgi.com/software/performer/
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