If I read an FLT created with Terrex (where geometry is attached directly to a LOD) and try to save it using the OpenFlight API the mgAttach command fails when trying to attach a LighPoint record (as it is in the original FLT) to a LOD record.

The displayed error message is:

E: Attempted attach to invalid parent level.

That is correct. Light points can be attached to groups and objects but not LODs. This behavior is similar to that in Creator where this kind of attachment is disallowed. Try creating a group or object between the LOD and the light point(s).

Also you can use mgValidAttach to learn other "attach" rules. You give this function a parent and a child level and it will tell you if the attachment of a node of the child level would be allowed to a node of the parent level.

I need to know “a priori” all rare cases (like the case of this topic) where the attachment could fail. Are there any other cases I should know?