IntersectionVisitor set LOD selection mode as USE_HIGHEST_LEVEL_OF_DETAIL is not working

[ChenKe404]

I want use IntersectionVisitor to do intersection with highest level detail of LOD, so I call setLODSelectionMode(USE_HIGHEST_LEVEL_OF_DETAIL),but the results always the current rang LOD.
the code for setting the mode:

    osgUtil::IntersectionVisitor iv;
    osgUtil::PlaneIntersector pi;
    iv.setTraversalMode(osg::NodeVisitor::TRAVERSE_ACTIVE_CHILDREN);  // Neither will TRAVERSE_ALL_CHILDREN
    iv.setLODSelectionMode(osgUtil::IntersectionVisitor::USE_HIGHEST_LEVEL_OF_DETAIL);
    iv.setIntersector(pi);
    iv.apply(*modelnode);  // modelnode is the root node

somebody help?

[ChenKe404]

OSG version 3.6.5

[ChenKe404]

I see,I need to set a read callback to read high detail LOD files.