[osg-users] Can't write to ALPHA component with custom fragment shader in RTT pass

Guy guy at dvp.co.il
Mon Mar 9 23:29:13 PDT 2009


Hi,
 We write to all the channels and there doesn't seem to be any trouble.
But be carefull, if u write to the alpha channel and blending is on, it
will use these values. Can't you write your data into other channel or
to a separate image (another attachment like COLOR_BUFFER1. in the
shader it becomes gl_FragData[i] where 'i' is the index of the color
buffer you want to set).

Guy.


>OK, but I'm talking about a pre-render pass to an FBO though. The FBO
is
>attached to an RGBA texture, and we want to be able to store some data
>in the alpha channel... So we want what we write to gl_FragColor.a to
>make it into the texture directly. Is there a way to do that?

Never used FBO, but guessing it simply switches the destination address,
and the pipeline still operates the same way  (??).
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