[osg-users] unrendered objects creating performance problems?

Joseanibal Colon Ramos jcolon at email.arc.nasa.gov
Tue Sep 9 19:07:19 PDT 2008


Hi Gordon,

Those are great questions, thank you. I do not think my terrain tiles have
their own geode or node, and maybe that can be a reason why the unneeded
tiles are not being efficiently culled. I my terrain is maintained as a
single geometry (which would be as you say: I am keeping the whole tri'
under one node), but it IS a Paged LOD terrain in '*.ive' format and it is
clearly divided into tiles for every level of detail. I thought that OSG's
database pager would take care of culling unneeded tiles for me... How
would you advise I break up the terrain as a distributed node-graph? Can I
load it that way at run-time, or do I have to re-create the terrain
differently? Thanks for your insight, I think, this is the right track!

-Jose


On Tue, September 9, 2008 6:19 pm, Gordon Tomlinson wrote:
> Have you broken your terrain in to tiled regions such that each tile has
> its
> one geode/node and uses an distributed node graph so that nodes that are
> not
> need can efficiently be culled, or do you have all the tri' under one node
> ?
>
> ( is your scene graph more like the top one in this basic diagram
> http://www.vis-sim.com/imgdp/vp_db_partion_01.jpg )
>
> Have you considered using LOD's, Paged LOD's OSV VPB ( aka osgDem )
>
>
> __________________________________________________________
> Gordon Tomlinson
>
> gordon at GordonTomlinson.com
> IM: gordon3dBrit at 3dscenegraph.com
> www.vis-sim.com www.gordontomlinson.com
> __________________________________________________________
>
> -----Original Message-----
> From: osg-users-bounces at lists.openscenegraph.org
> [mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of
> Joseanibal
> Colon Ramos
> Sent: Tuesday, September 09, 2008 8:08 PM
> To: OpenSceneGraph Users
> Subject: [osg-users] unrendered objects creating performance problems?
>
> Hi all,
>
> I was hoping someone has an idea about why I am encountering the following
> problem: I have a big terrain and on certain viewing angles it contains a
> huge amount of triangles to draw and puts a big strain on OSG's
> performance. I tried playing around with near/far clipping planes to
> improve performance, by cutting out a lot of the rendering, to the point
> only a very small fraction (and even none at all) of the terrain is seen
> through my camera. OSG's framerate, however, behaves just as if I was
> looking at the whole thing and drawing all the triangles.
>
> At certain angles, the framerate increases (where small number of
> triangles would normally be - even thought I don't see anything),
>
> and at other angles, it decreases (the same angles at which the viewer
> normally tries to draw a large number of triangles - even though I can't
> see anything). What is going on here?!? help!
>
> -J
>
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