Stupid question, I'm sorry...

[salt サルト]

So the question is :
Is it necessary to triangulate my mesh? ( from polygons to triangles )
If no, thats mean I can export my mesh to game with squares / polygons faces ?

[HellJumper]

It automatically triangulates your model when you export to .smd (or if you don't export to .smd, the game automatically triangulates your model). The reason for this is that 3 points can only ever make a flat surface whereas 4 can make 2 flat surfaces.

Example:
http://i.imgur.com/BSCQ9PB.png
http://i.imgur.com/lCLn9w2.png