Thank you Paul(s), Stefan and Gordon, yes now I am pretty sure that Robert by "quadtree" meant a node organization strategy (that's why I said "...or a particular parent/child layout for OSG nodes?" in my second email) and there isn't any "real" quadtree support in OSG but it seems that one can simulate quadtree-like (or octree-like) structures using the hierarchical bounding box mechanism of OSG's nodes.
The problem was that I expected OSG to be able to do a per-Drawable culling over the Billboard (and Geode), instead it seems that the culling is done only per-Node, and since I put all the drawables under the same billboard Node the culling is of course performed on the whole block which explains my results and Paul's results. So if I am not wrong the Billboard node and the Geode node are the smallest cullable entities, which can be annoying at times since one has to create a large number of extra nodes to achieve proper culling. I have also another important doubt though: is the hierarchical bounding box tree (HBBT) kept up to date frame by frame? I have this doubt because billboards by definition rotate following the camera and thus potentially modify the HBBT. If the HBBT is not kept up to date taking in consideration the billboards rotation the whole frustum culling mechanism could become inconsistent producing wrong results (object popping in and out). Dunno if I was clear enough, if anyone is interested I can send a simple picture explaining better what I mean. Thanks very much to every one, Michele On Fri, May 23, 2008 at 7:11 PM, Paul Martz <[EMAIL PROTECTED]> wrote: > Thanks for the example code. When I bring it up, I get cull ~5ms, and draw > ~15ms. I then use the middle mouse button to drag all the billboards off the > screen, and I get cull ~0.1ms, and draw ~0.3ms. So, obviously, frustum > culling is working. > > However, performance is a cliff that only drops off when all billboards are > offscreen. This tells me something is wrong in the organization of your > scene graph. There is already quite a bit of discussion regarding that on > this thread. > > When the data in your scene graph is spatially organized, you should see > cull/draw times ramp down as the amount of visible data decreases. > -Paul > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
