> I was hoping for something better. Even just a BSP tree or something.

My previous post outlined one way that this could be implemented. Go ahead
and try it out; if it dramatically boosts performance, then please submit it
back for inclusion in OSG. This is how open source works. Complaining about
the lack of a feature won't get Robert to drop everything and implement it
for you.

If your ideas for improving culling in OSG are really worthwhile, then it
should be fairly easy for you to drum up a couple of clients willing to fund
its development. If no one wants to fund your idea, then maybe most users
are satisfied with the performance obtained from the existing code, and your
idea is not worth the implementation expense.

> The reply about OpenGL occlusion query was hopeful, but 
> that's on someone's todo list apparently. That approach 
> doesn't impress me a whole lot either ...

It's on my todo list. It's a funded development effort, so apparently it
impressed someone. It has already passed early beta tests with
model-dependent speed improvements in the 2x-10x range.

> ... unless you're going to 
> implement HZB or something really worthwhile - I'm not sure 
> if anyone has ever really made progress with that either.

?? I think you've answered your own question here. If the hardware supports
a fast z rejection, OSG implicitly uses it, not just for my occlusion query
work, but in all OSG rendering. However, in my experience, this is a
model-specific issue. Some models render faster sorted by state, others
sorted front-to-back. OSG lets you select either.

As for the rest of your email, can I share an abbreviated version of my
experience with scene graphs?

As an experienced OpenGL developer, I was strongly opposed to my previous
employers' usage of scene graph technology. I wanted more control in the
software we were developing; the scene graph just seemed to insulate me from
what I wanted to do. I did see one benefit though -- built-in support for
loading models in many different types, something raw OpenGL has always
lacked. As I used scene graphs more and more, I found they offered a lot of
flexibility and features to developers that would've otherwise required
coding by hand. Currently I do most all 3D development using scene graphs
exclusively. I'm a convert.

I hope you will take the time to see the benefits as well.
   -Paul

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