Realistic Face Stickers for Spark AR

Hello everyone!
On Instagram you have so many filters with face stickers or tattoos. Some of them look really good like they are actually on the skin while others look like they are more floating on top and you can see the face mesh quite well.
What is the difference? Is there a way to make face stickers without using a face mesh?

Thanks a lot!

I don’t know about making them without a facemesh but I would imagine the ones that are better integrated to the face make use of normal and specular maps. The aim here would be to recreate some skin definition and lighting using those two texture slots respectively, so as to avoid the sticker looking flat or too perfect.