Hi PP, yeah the easiest method will be to make those surfaces into solids by extruding them by a small distance as Steve mentioned above.

When your object is a solid that encloses a volume, MoI will automatically set the normals to point towards the outside of that solid.

When you only have open surfaces in MoI that do not enclose a volume, there isn't really a good way for MoI to automatically decide which side of the object is meant to be the "outside" part, so with open surfaces it is possible for the normals to be pointing in either direction. Which direction it is will depend on things like whether you initially drew the initial curve in either a clockwise or counter-clockwise orientation.

Often times there is an option in rendering programs to do a "2-sided" rendering where it will display both sides of an object instead of just only the positive normal side. I'm not sure if Messiah has an option to do that, but if it does you would probably want to just set that option and then you would not need to worry about this issue - that's why for example when you imported into Cinema4D the objects with reverse normals are showing up in C4D, because it does not only display one side of the object. It's kind of easier to set this option when it is available.

If there is no method in Messiah to do 2-sided rendering or display then that makes it even more likely that you'll want to extrude your objects into solids so that they won't just disappear when your camera rotates around them in an animation or stuff like that.

Re: Modo/Lightwave option for vertex normals on LWO export - that actually controls something slightly different - the "vertex normals" of a mesh are used for shading and are normals that are attached at every vertex of the mesh. Those are in addition to the face normals that indicate which direction the entire polygon mesh face is facing.

- Michael