Hi,

  i read that VirtualPlanetBuilder will support Layers. I'm developing a
GIS component with OSG and i also have to incorporate layers. Unfortunately
i can't wait for the release of VPB with this feature, so i need to use OSG
and develop it myself.

  How can i control the rendering order of the layers or how can i control
the render order of the nodes? I know OSG does it automatically, rendering
first the opaque bins and then the transparent, and also ordering by z.

  My first approach was having the layer be a Group node, and add all the
contents of that layers like children. This approach failed when i did have
a lot of children, because of the culling, that dropped the framerate. So it
is a must to optimize how the children are added to the group, using an
structure like the quadtree for culling. So, another question is:

   How can i control the culling process? How can i avoid the cull visitor
to traverse the children of a node? I tried to disable culling by setting
CullingActive to false, but the children were visited also. I tried that
because a had only a single instance of Geometry shared with all the
children. The difference was that each child had an AutoTransform node to
control the position of the geometry (and the screen alignment). The cull
was more than ten times slower than the draw (stats) even if all the
children were visible and not culled.

 Any comments or suggestions about the design of incorporating layers to
OSG will be also very helpful and appreciated. :)

Thanks in advance.
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