LOD node for VRML/X3D >= 2.0. This is not for VRML <= 1.0 LOD node.
It's a common ancestor for VRML 2.0 LOD (TLODNode_2) and X3D LOD (TLODNode). Unfortunately, we cannot have a simple common class for both VRML 97 and X3D because there would be a name clash for "level_changed" event:
For VRML 2.0, main MFNode field was named "level" and so "level_changed" is an event reporting when MFNode changed.
For X3D, main MFNode field is named "children", and so "children_changed" reports MFNode changes. "level_changed" is a new field, SFInt32, indicating which child is chosen.
So level_changed has completely different meanings for VRML 97 and X3D. As an extension we'll add "levelIndex_changed", SFInt32, to be analogous to X3D "level_changed". This way both VRML 2.0 and X3D LOD nodes have the same capabilities, and common interface for programmer (programmer should use X3D event/fields names for Pascal property names), but for parser they will use different names.