Hi Gep - if you could post a sample model of some small piece your model that does not work right, or even a screenshot of what you are seeing that would definitely help, because I can't really understand what you are seeing by just the description of a mess.

One thing to watch out for is if you do any transformations to the objects after you have imported them into Modo, make sure you are in "item" mode when doing the transforms.

Otherwise if you do something like transform all the vertices Modo does not transform the vertex normals in that case and you end up with a vertex normal map that doesn't match your geometry anymore and that will make for weird shading.

Also usually it is best to not separate your model on export - you usually want to keep things joined together because the mesher will do extra work on joined edges to make sure there is a unified mesh structure between the surfaces. If you have 2 surfaces that are just sitting right next to each other but not actually joined, then they will get meshed separately and they may have different vertex structures on curved edges, leaving little cracks between them. That won't happen if you have them joined though.

If you need things separated, it's better to separate them in Modo after you have imported them.

But if you can please provide a sample model or at least some kind of screenshot that helps to illustrate what you are seeing, that would be a big help to be able to give you some better tips.

- Michael