Half : you can use the file OBJ from CAD program, (MOI) change Material, render but not edit the object else you lost the original Vertex normal! ;)

http://www.blenderartists.org/forum/showthread.php?299193-Modified-OBJ-Importer-for-Custom-Vertex-Normals Code By Zalamander

without code

with code

<img src="http://s6.postimg.cc/9wg34nya9/casque.jpg" />