osg细节裁剪

一个Geode里面只有一个点的时候，默认情况下是看不见的，

1. osg::CullStack::CullingMode cullingMode = viewer.getCamera()->getCullingMode();  
2. cullingMode &= ~(osg::CullStack::SMALL_FEATURE_CULLING);  
3. viewer.getCamera()->setCullingMode( cullingMode ); 

http://blog.csdn.net/lainegates/article/details/7459161