This is one of my favorite bits of incredibly clever fuckery that goes on behind the scenes of 3D modeling, and I have an intense compulsion to talk about it right now.
If you've never seen the true geometry of the merc models, you're probably wondering what the hell is going on with the one on the left. Minecraft Steve 3D-printed looking motherfucker.
Believe it or not, it's the exact same model as the one on the right. The light is just being instructed to interact differently with its polygons! The one on the left is being given flat shading, while the one on the right is being given smooth shading.
The mercs have far fewer polygons than you probably think they do. And that's not just because the game was made in 2007! Most stylized faces probably aren't going to have many more polygons than this, especially faces designed for video games. Thanks to the magic of smooth shading, they don't need more than that.
So how the hell is this possible?
I'M GLAD YOU ASKED! Class is now in session!