Re: Clipgen and alpha channel in clip textures

From: Simon C Mills (simon++at++wgs.estec.esa.nl)
Date: 12/13/2001 06:52:46

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Eric Sokolowsky wrote:
>
> On Thu, 13 Dec 2001, Simon C Mills wrote:
>
> > Hi Performers,
> >
> > this is not strictly a Performer question but I wouldn't know where else
> > to ask.
> >
> > I'm using Clipgen (version 1.1) to generate clip textures to be used in
> > a performer application. I wanted to use an alpha channel in my clip
> > texture just like in a normal texture. However, it appears clipgen masks
> > the RGB values in the produced clip texture tiles with the alpha channel
> > ie. where alpha is 0, RGB values are set to 0,0,0 and are not left at
> > their original values as I want. I tried on the Inset tab to set Alpha
> > Mask to Feather Edge with 0 pixels and also to give an Alpha Mask image
> > that was pure white. Neither of these helped. How can I tell clipgen not
> > to do this?
>
> You are probably creating the cliptexture as RGBA 5551, which means 5 bits
> for each of R,G,B and one bit for A. With one bit, all you get is on or
> off. You can change this on the first screen (the "Define" tab) of clipgen
> with the "Int Tex Format" parameter. I'm not sure if you need to change
> the "Ext Tex Format" parameter as well. Just select "RGBA 8_8_8_8" instead
> of "RGBA 5_5_5_1". Of course, this takes more texture memory to store.

Thanks eric. I didn't mention it but I was already doing this although
all I need from my alpha channel is on or off. I was using internal and
external format of RGBA 8_8_8_8 i.e 32 bit and not 16 bit. Needless to
say but it doesn't seem work.

Regards, Simon
_______________________________________________________________________

Simon Mills
Modelling & Simulation Section (TOS-EMM) Tel: +31 (0)71 565 3725
European Space Agency (ESA/ESTEC) Fax: +31 (0)71 565 5420
Postbus 299, 2200AG Noordwijk e-mail: Simon.Mills++at++esa.int
The Netherlands http://www.estec.esa.nl/wmwww/EMM
_______________________________________________________________________

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