Hi to everybody!
I have a question.
I use 3ds max as software for modelling my projects.
As I saw in a lot of tutorials, at every object in the scene must be applied an Unwrap map, before exporting and importing in U.E.
Is this action NECESSARY?
In a project with many elements and meshes this operation could request so much time, so i was wondering if I can skip this step.
Thanks for the answers!
short answer: yes.
Longer answer: yes, yes it is.
Cant make it any better.
Just keep practicing, trying, learning, and eventually it will get easier and faster 
As I know there must be UV mapping on an object. It’s necessary for texturing. But unwrap is just one of texturing techs.
I can be wrong, cause I’m programmer but not 3D artist.
There is some strange things when using several texture channels and precomputing lightmaps in UE, but I can’t explain details.
So, no, it is not necessary. But it’s necessary to have UV coords on the model.
And, besides, using unwrap is a good practise.
I suggest you read the question again.
Because saying no, its not necessary is wrong on so many levels.
Essentially, yes, you need to unwrap everything before bringing it into Unreal, but there are some exceptions to this rule.
1 - You can bring in the meshes without them being unwrapped if your artist is finished with them but not with the unwraps/textures, in order to start working with the meshes right away. You will have to “Reimport” them later, which can be a hassle, but it is possible to bring the meshes in first and then get the updated version at a later point in time. Especially as it pertains to UV unwraps, this is NOT good practice and should be avoided unless you’re working on a project with a REALLY condensed development cycle.
2 - If your object only needs things like base material attributes, then I suppose the unwraps don’t have to be very good. But if there is any sort of textural detail, yeah, you’re going to need to unwrap your object and do it right.
That said, unwrapping objects is not as hard as it probably seems right now. Max is… okay… for unwrapping. I personally prefer Maya’s tools for it, and Zbrush has a really nice unwrapping workflow too.
Thanks for the answers and for the tips, I will use the unwrap tool!