Hi James,
On 14 January 2014 22:37, James Turner <[email protected]> wrote: > What is the mechanism by which the compile step happens for a Geometry (or > any Drawable) added to the scene after setSceneData and the > CompileOnNextDraw mechanism? Because I’m not seeing it from a static > reading of the code (but of course I can have missed it), and the runtime > result I observe suggests it’s not occurring either. > A compile traversal doesn't happen every frame, it happens by default on the first frame of rendering and when the pager uses the osgDB::IncrementalCompileOperator. It's the compile traversal that calls the compileGLObjects() method. > (Of course, if the compile step isn’t necessary for VBOs to work, this is > a red-herring anyway) > If compile traversal isn't called for an object it'll just compile what is required when the geometry is rendered, so there is no functional need to force a compile traversal. One uses a compile traversal for performance and load balancing reasons, something that is usually only critical for real-time visualization applications such as games and simulators. > > The meta-point is that I don’t see any performance change when enabling > VBOs, and the profiler results on Mac suggest that the Geometry in question > is still on the traditional (non-VBO) glDrawArrays path. In my specific > case VBOs may or may not help a particular performance problem, but most of > the ways I can imagine to fix my user-level issue will work much better if > VBOs are actually working as expected. > glDrawArrays can be used when using VBO's without any problems, they are completely compatible in OpenGL and the OSG. Robert.
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