Hi,
Jean-Sébastien Guay wrote:
Hi Jim,
Not necessarily. If the object-that-is-supposed-to-be-transparent
still has depth writing enabled, it will overwrite more distant objects.
Then there's which blend functions are enabled which
can alter the output of the fragment shader.
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?
>
> (in effect, we want to be able to write to 4 floats per fragment)
Yes, this is definitely possible, but why stop at 4 :).
Have a look at the osgstereomatch example and its shaders. Have a look
in the readme at the section "Multiple Pass", there we want to simply
store 16 values into 4 textures (MRT) during the subtract pass. In this
case the alpha channel behaves exactly as the RGB channels.
Also investigate the use of gl_FragData versus gl_FragColor for writing
unclipped values.
rgds
jp
Thanks,
J-S
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