Example for selection sub entitiy and more lower level:
var opt = new tlib.OdTvSelectionOptions();
opt.setLevel(tlib.SelectionLevel.kSubentity);
opt.setMode(tlib.SelectionMode.kCrossing);
var selectionSet = viewer.activeView.select([0, 0, 1920, 1080], opt, viewer.getActiveModel());
var itr = selectionSet.getIterator();
for (; ! itr.done(); itr.step()) { var subEntity = itr.getSubEntity(); console.log('sub entity'); }