Thank you for this information, Matt!
Hm, i know what i want but as it seems i'm pretty bad in explaining it.
The clouds were only an example of how this 'effect' looks like.
Quote:
can you try to find a better picture, one that looks more like what you want?
Ok, this one is better, i think: (click to enlarge)
Probably this one is an good example too:
Imagine this tree was a model with leaves made out of many meshes. With gouraud shading every mesh would have a light and a dark side but in this picture the hole tree (model) has only one light and only one dark side!
I hope this was clear! 
