How optimize mesh (minimize tris and vertics)

I had a big model with 3,1M tris and 4,9M vertics. I want optimze mesh, short count tris and vertics. How do it?

 

what kind of model is that? hard surfaces -> modular way, anything else -> decimate + normal map.

 

I hava big model, all mesh have the same material with Standart Shader, all objects static.
http://prntscr.com/8k7t7c

 

Go for modular design imo.

 

May be exist some solution to short count of vertics of meshes.

 

Seems like a lot of polygons, show us the wireframe if you can.

 

Example http://prntscr.com/8kerlu

 

from closer if you can, just to tell if you are wasting polygons.

 

That's too big for Occlusion and LODs. You going to need to break it up into pieces in the first place.

 

How split mesh of the big model by the several parts using unity editor?

 

You can't unless you have some assets from Asset store I think. Better split them in your tool where you made them.

Also for modular design, take a look here:

http://wiki.polycount.com/wiki/Modular_environments