Facial lighting in games

[progmars]

I enjoy playing games with high-quality textures, but what disappoints me is how weird sometimes human faces are lighted. It is especially weird because textures are good and generally lighting is pretty good on all other objects, but facial lighting makes me cry, it has so obvious problems. And I mean some high rated games like Mafia II, GTA 4, True Crime: New York City.

Look at this one:


It seems so completely wrong that his forehead is brighter when it should be darker because his hat has to create at least some minimal shadow.

And I have seen such weird situations with human faces so many times. Sometimes the light is coming out of someone's mouth like he is having a lightbulb somewhere deep in his throat
And many times the face is lit in a way that looks like if the lite is coming from the floor, but I see that all in-game ligths are on the ceiling!

I am really curious, what causes this? Is it because of lighting algorithms of modern graphics cards?
I know, it would be much to ask photorealistic quality in real-time, but such obvious lighting quirks somehow seem a bit too disappointing.
Or maybe it is game artist's fault? Or maybe programmer's?
And how can I avoid such lighting problems in my 3D projects?

[Shockeye]

They probably dont want the performance hit of calculating hat brim shadow

[jacmoe]

It's obvious:
The guy has a tan only in the areas not protected by his hat..

[Jabberwocky]

Self shadowing artifacts can be really ugly. You get this nasty flickering, pixelated, depth-fighting crap that looks horrible. The latest game I played that it was really noticeable in was Assassin's Creed (across the whole environment).

So in this screenshot, they've likely disabled shadow casting or shadow receiving on the face or person as a whole, in order to avoid the shadow artifacts. It's the lesser of two evils, if you ask me.

[progmars]

The guy has a tan only in the areas not protected by his hat..

Nice idea.

Actually, if thinking a lot about each bug, maybe every bug can be turned into some feature. Once I tried to generate a certain kind of audio signal and did some mistake in calculations. But when I opened the generated audio file and looked at its spectral view, I was amazed: the view looked like some really cool complex pattern. I could never create something like that without my buggy formula

Self shadowing artifacts can be really ugly.

I am still a bit new to the advanced 3D topics. Thanks, now I'll know that those problems are called "self shadowing artifacts", so now I can research how other developers deal with it.