Re: trouble with transparent textures

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Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Tue, 25 Feb 1997 03:39:15 +0000

On Feb 24, 1:57pm, Edward Peters wrote:
> Subject: trouble with transparent textures
>
> Howdy,
>
> I'm using Performer 2.1 on an IR Onyx running IRIX 6.2
>
> I'd like to map an rgba texture onto a piece of geometry, so I've added
> the following calls when I build my geoset and its corresponding
> geostate:
>
> gState->setVal(PFSTATE_ALPHAREF, 0.0);
> gState->setMode(PFSTATE_ALPHAFUNC, PFAF_EQUAL);
> gState->setMode(PFSTATE_TRANSPARENCY, PFTR_ON);
>
> From the Performer Programmer's guide, I'd expect areas of my texture
> with alpha=0 to be transparent, but instead nothing is drawn (the whole
> thing is transparent!) If I remove the above calls I get normal texture
> mapping (but no transparency).

It sounds like you have alpha information elsewhere, for example in the
COLOR4 attibute information or the material. Make sure the material and
each COLOR4 geoset attribute has alpha == 1. This should do the trick.

>
> Can anyone offer suggestions? Texturing is awfully complicated, and as
> verbose and readable as all the gl and performer man pages are :) I'm
> coming to the end of my ability to comprehend.
>

Hang in there, you'll find it easy in the end.

Cheers,
Angus.
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