What are the lines called when they're used to define geometry without changing the overall silhouette, like the lines on the knees of the green haired girl, the ankles on the blue haired girl, or the folds on the clothes in the spoiler in >>4964
I noticed it's not everywhere, like >>5280
hardly has any besides the clothes.
But then there's the third picture in >>5339
which has lines on the ribcage that aren't exactly outlining any anatomy.
I think another common example would be noses, though there seems to be a lot of stylistic freedom and variation in how people draw noses. Regardless, when you're not viewing a face from the side, I don't understand how someone draws in that part of the face.
Is this just anatomy and it's a stylistic choice if you add it? How would you approach drawing such details, especially when they don't change the underlying silhouette? Is it understanding lighting well or are their tricks / hacks to it. I have a feeling this might change completely when using color, cause you have more than lines to work with, and you can actually draw the geometry of these features better with a gradient of light. But I've only been using pencil (sometimes pen) and I don't quite understand this part.
might have partially answered my own question while trying to describe it