Well.. VBO can be used with display lists together, i think, yes?
No, VBOs are meant as a replacement for DisplayLists. Though my experience tells me, that display lists are still faster.
Using display lists together with VBOs would mean a lot of wasted memory, since the VBOs would not be used instead for the first frame, where the display lists are recorded.
4913 is max vertices count for 16x16x16 chunk using indexed geometry.
1446 for solid chunk; 578 for one side exposed.
Thanks, good to know the exact numbers.
OpenGL picking is not very good probably... (I tried it, even rendering custom scene for it, without materials) but talking about geometry groups i found that i can check picking against chunks at first then choosing concrete block. Am i able to use xith's software picking in a custom way? probably 1) setup chunk's boxes, 2) run picking 3) setup boxes from picked chunk 3) run picking... Or some faster direct way...
Check the PickingLibrary's methods. Some of them take interface implementations for pick testing. Hopefully this helps you to customize the behavior.
But early group testing is done in both picking strategies (OpenGL- and software picking). So I don't expect, that you can optimize the code except of you use more complex group nodes like tree implementations. But if you can optimize the code, please share your improvements.
So now the primary question: Can I use xith's picking and frustrum culling (some methods) directly for a some custom "box" (group of chunks->chunk->box->etc.. slowly narrowing choice)?
The picking system is not designed to be used standalone. But all the frustum culling test methods come from OpenMaLi. So you can use them even without Xith.
How to disable sorting (all boxes are opaque)?[/b]
Have a look at the render options. They should allow you to change the sorting strategy or disable it.
And no, I'm still not aware of direct access options.
The BranchGraph should provide a callback to render directly. If you can't find it, I can look it up when I am at home.