Hi,

I ran into something weird, or something that I don't know how it works exactly.

What I want to do when rendering to multiple targets is that I selectively 
write to certain color buffers in my shader, but leave others alone. 
for example 


Code:
gl_FragData[3] = vec4(0,1,0,1);



without setting the fragment data for the first 3 buffers...

This doesn't seem to go well. for example, if I don't explicity set a value in 
the color buffer 4, it seems to copy the color value from the first color 
buffer for some reason instead of leaving it alone.

So I though: ok I HAVE to explicitly set all a value on all used color buffers, 
so then if I don't want to touch one of the buffers, I just use blending and I 
write a value with an alpha of 0, so it doesn't effect the buffer. This doesn't 
work as expected.

It seems that the blending only looks at the color buffer 0 ? if I write a some 
color-value with an alpha of 0 to the color buffer 0, it doesn't seem to matter 
what I write to the other buffers, it doesn't write anything.

So not sure if you can follow what I'm explaining, but bottom line is: I would 
like to selectively write to certain color buffers in my shaders, and leave the 
other alone. Any ideas on how to do that properly? Or am I trying something 
impossible and do I need another solution?


Thank you!

Cheers,
Bram

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Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=57121#57121





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