Let's say I already have a character model. Now I'd like to add something like this on his upper arm:

enter image description here

I don't know where to start. I guess I can use some sculping brush to make the surface bumps...? But I don't even know how to make the "base mesh" to start sculpting. How to make such irregular shape wrap around the upper arm? Or is it possible to use normal map to achieve this without modeling at all?

  • 2
    $\begingroup$ You could do this with shaders and normal maps. Blender even lets you have multiple UV maps so you could overlay this as a decal. $\endgroup$
    – Ron Jensen
    Commented Aug 23, 2021 at 2:24
  • $\begingroup$ Yes, as Ron Jensen says, the best, in order to keep your file as light as possible, is probably to sculpt then bake the normals and use the normal map to fake the 3D relief on your arm $\endgroup$
    – moonboots
    Commented Aug 23, 2021 at 6:15
  • $\begingroup$ @RonJensen Thank for your replies! But I'm still a little confused. As you can see that part has a different material than skin. Let's say it's metal. How can I do that? I know I can specify a new material to some faces, but the arm mesh doesn't have faces that form this irregular shape... $\endgroup$ Commented Aug 23, 2021 at 13:35

1 Answer 1


If you want, you can make a second UV, here you can see a UV that just covers the center of the cylinder. On this UV, the rest of the verts were mapped into a corner so they'd all be black. This technique is optional, but it lets you devote a full image to the overlay. Optionally make an extra UV

This screenshot shows texture painting the overlay onto the original object. Texture painting

Finally, the shader setup. You might want to do this first so you can see what you're doing. The non-interesting parts are collapsed, basically there is a mix shader being controlled by the mask I texture-painted above. I didn't take any time blending edges or perfecting the bump, this is just a basic voronoi texture, but I think it gets the point across. Shader setup


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