How can I create veins on skin I have this character's arm.




I want to have some veins in this pattern with a shape-key, meaning that the basis would be without the veins and when the shape-key is on, the veins would appear. I also don't want to have too many vertices, my computer isn't the best, and I have many other meshes in scene.



Any ideas on how to do this?
I'd do it in the material via a normal map / bump map.