It's a very old trick, I didn't invent it but maybe somebody will find it useful:
In the image above, there is one torus without anything special done to it with a white surface.
Then the torus is duplicated, it's normals inverted (Geometry -> Flip Normals), and in its (Unique) material all settings are zeroed out so it's full black.
Then in the Material -> General -> Two Sided is unticked (so you don't see the front, only the backside).
Then as a last step, you use Displacement, usually without, but optionally with additional subdivisions to give the inklines more detail, set the Center to 1 and apply some texture map that will give you the structure you want for your inklines - something smooth and with little detail for soft strokes or something with more detail like in the above image (I used some asphalt texture that I just stumbled across). If you want inklines without variation, just use a solid black image.
Then you adjust the height to taste, it defines the thickness of the stroke.
If you set Center to something more like 0.5, you can also get little strokes all over the surface, but that needs more defined textures and probably more subdivisions so it looks good.
If you wonder why I use a Center value of 1 and a black texture: Since the normals are inverted, the displacement also goes into the opposite direction, so you have to revert all the usual rules.
Note: This trick works best with rather roundish objects. With more rectangular stuff you may get strange effects.
And if you have a texture painting app: You can paint the thickness of your strokes as a greyscale texture for instance onto your character, so that in the face or on the hands the strokes are thin and on the general body they are wider.
Here is a very simple example file that uses a Perlin Noise so I don't have to worry about textures: One Problem ATM is, that it does not work in Presto and I just learned that the devs contemplate removing the Two-Sided option from all engines
http://thearender.com/forum/viewtopic.p ... 77#p148676
I hope they reconsider, since one of the best things about Thea is it's flexibility and if it ever wants to get into the production market, things like this make quite a difference.
Fingers crossed...
Cheers,
Tom
