Thanks Robert, This is an odd corner-case I guess, I want the LODs to be selected based upon global distance from the eye-point. For various reasons, onscreen size is inappropriate as a selector. I think I can put together a small example/patch and send it in for review.
cheers, sean _________________________________________________________ Sean Spicer Executive Vice President & Chief Technology Officer Aqumin (www.aqumin.com) Office....+1.713.781.2121 Mobile...+1.713.447.2706 Fax.......+1.713.781.2123 On Fri, Oct 9, 2009 at 2:06 AM, Robert Osfield <[email protected]> wrote: > Hi Sean, > > You are correct the range distance of LOD's are in the LOD's own local > co-coordinate system. This is appropriate as you almost aways want > LOD's to scale relative to a screen size, and doing the calc in local > coordinate allows you to decorate subgraphs with LOD's with transforms > that scale up or down the subgraph and still have the LOD ranges > computed appropriate for that new scaling. This behavior is key to > get a scene graph to be well encapsulated. > > It sounds like in your case you have transforms above your LOD's that > scale your objects, but you still want their ranges to set in world > coords, that ignore any transforms. This would present the problem > that is the transforms scale change then the LOD would choose > different children - choosing an in-apprioriate level of detail for > the on screen size. > > Robert. > > On Fri, Oct 9, 2009 at 5:21 AM, Sean Spicer <[email protected]> wrote: >> Studying the source a bit harder, I think the range-distance is >> definitely in Object (local) coordinate. The distance calculation >> (osg::LOD.cpp) is: >> >> required_range = nv.getDistanceToViewPoint(getCenter(),true); >> >> where getDistanceToViewPoint is (osgUtil::CullVisitor.cpp) >> >> (pos-getViewPointLocal()).length()*getLODScale(); >> >> So, this raises the question: is there a good reason why there is no >> option to specify the LOD range distance in World Coordinates? This >> would make complex LOD graphs like the one I'm working on much, much >> simpler. Perhaps there is another method that I just do not see? >> >> cheers, >> >> sean >> >> On Thu, Oct 8, 2009 at 10:50 PM, Sean Spicer <[email protected]> wrote: >>> >>> This may be a simple question - is the LOD range distance specified in >>> object or world coordinates? I seems as if it should be in world >>> coordinates, but I've got an example with numerous LOD nodes in sub-graphs, >>> and if I sent a constant distance range in each of them (0.0, 30.0f) so >>> that each LOD node has the same range - the LOD switch only behaves as >>> expected if the transforms above each LOD node are identical. The moment I >>> have a scale matrix above the LOD the switch becomes dependent on the >>> scaling...e.g. larger LODs switch before smaller ones. This leads me to >>> think that the LOD range distance is in object coordinates, and needs to be >>> scaled by the localToWorld transform. >>> I've had a look at the source, and it seems logical (not to mention that >>> I'd be shocked if someone hadn't had a problem before this if it were >>> incorrect) Comments? Thoughts? >>> cheers, >>> sean >> _______________________________________________ >> 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 > _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
