[osg-users] Scaling down a subgraph including frustum clipping: ClipNodes?

Alexander Löffler alexloeffler at gmx.net
Tue Sep 2 03:25:27 PDT 2008


Hi all,

I want to scale down a subgraph of my scene (everything below the Transform that 
scales it) to a smaller size inside the view frustum. The tricky part is that 
only those parts that are currently visible in the original full-size scene 
should also be visible in the scaled-down version. This means, the clipping that 
is applied at the clipping planes of the view frustum should also be applied to 
the smaller version. The whole process should be done multiple times on a 
different subgraph each, i.e. the result would be my regular view containing 
several scaled-down scenes, each clipped to its own clip planes.

I looked at the osgclip example, which already looks quite promising, so the 
ClipNode is probably what I want. (I didn't really understand why culling is 
disabled in the example, though. Switching it on again didn't change anything 
visibly.)

Are there some kind of limitations to the ClipNode, imposed by the underlying 
glClipPlane? Like a maximum number of clip planes in the entire scene, or does 
the performance drop hugely for each additional clipping defined like that?

Thanks a lot for your help,
Alex.



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