[osg-users] How do I access the Z-Buffer content from the last render pass

[Daniel Holz]

Hi osg-users,

is it possible to access the Z-Buffer content from a render pass 1 in 
the shaders during a second render pass 2 if I do not clear the Z-Buffer 
content in pass 1?

In my project I render my scene in pass 1 and set the clear mask for 
pass 2 to "0", hence not clearing neither the color nor the depth buffer:
   pCamPass2->setClearMask(0);

Now, how do I read out the Z-Buffer content of the gpu for a given pixel 
in the fragment shader of pass2?
Trying to read from gl_FragDepth did not work.

Any suggestions?

Cheers
Daniel

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