Hi John, When the cull traversal encounters a Transform node it has to transform the view frustum (and associated culling properties wrapped up in the CullingSet class) it the new local coordinates of the subgraph before it can continue traversing the subgraph. Entering and leaving the subgraph will also require the new CullingSet to be pushed and popped off a stack of them.
The cost of actual concatenation of the matrices is relatively minor. There is another cost born by using lots of transforms though - the OSG has to record all the combinations of projection and modelview matrices that will be used by the draw traversal, and during the draw traversal that projection and modelview matrices have to be reset as the traversal walks through the rendering graph. Changing projection and modelview matrices also means passing more data to OpenGL and changing state down on the GPU so there will be a GPU cost as well. So expect a higher cull and draw dispatch and draw GPU cost. The biggest hit will typically be in the cull. This is the cost of having lots of dynamical subgraphs. We've striven to minimize this cost over the years by making handing of transforms as streamlined as possible, to get any more efficient you have to start thinking about replacing transforms with other nodes. For you own app the really big question has to be do you need all these transforms. Using a thousand transforms visible on screen at once is unlikely to affect performance too much, using hundreds of thousands of transforms will be a problem. You don't say anything about what you are doing and why with your scene graph or the performance you are getting so I really can't say anything more about what you should do with your app, you'll need to pass on more info so others can make suggestions based on this. Robert. On Fri, Aug 13, 2010 at 3:57 AM, John Water <[email protected]> wrote: > Hi everybody: > > > I found that the more transform node, the higher cull time ?? > > is that correct ?? in one whole scene graph, transform node'cull time occupy > 60~70% in total cull time ?? > > any solution, thanks in advance. > > Thank you! > > Cheers, > John > > ------------------ > Read this topic online here: > http://forum.openscenegraph.org/viewtopic.php?p=30729#30729 > > > > > > _______________________________________________ > 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
