Create a normal maps for a character that already has diffuse map and UVs

Support Materials and Textures
1

Hi,

I looked online and on youtube for this but I didn’t found an answer.
I have a character that is UV unwrapped and has the a greate skin material. The situation is that the character has 4 materials ( legs, head, body and arms ), how can I create 4 normal maps for each part.

Thank you