Hi Robert,

> Invalid bounding sphere's disabling culling is deliberate design. It's for 
> cases where you can't determine the bounding volume and therefore can't 
> determine how to cull them as culling is predominantly based on a knowledge 
> of the bounding volume. 
> 


fair enough but as I demonstrated this design does not work correctly. Once you 
merge an invalid bounding sphere with a valid bounding sphere of a sibling, the 
overall bounding sphere becomes valid and thus setting an invalid bounding 
sphere to circumvent culling does not even work reliably.

For nodes you don't want culled you simply do "setCullingActive(false)", which 
works reliably, unlike the indeterminate bounding sphere way. I don't see why 
we need two features doing the same thing with one being slightly broken.


> Changing either behaviour will break existing OSG applications that rely upon 
> this.

Understood, but as I said we can add a new culling option that is off by 
default if the compatibility issue is too much of a concern.

Maybe another way to approach the issue would be marking bounding sphere's as a 
"null" bounding sphere as opposed to an invalid one. Unfortunately I can't 
think of a way to do so without adding overhead to each bounding sphere 
intersection test.

Cheers,
Jannik

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http://forum.openscenegraph.org/viewtopic.php?p=65707#65707





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