I'm trying to create a (Cycles) material that's based on geometry without doing any UV unwrapping or vertex painting:

enter image description here

I'd like to created a map based on depth into the brain folds to control the glowiness. Are there any nodes or workflows that could let me achieve this?



You are asking for an approach which avoids manually unwrapping/vertex painting, maybe the end result is more important than how you get there. For this spherical shape trigonometry offers a solution.

Nodes Approach

enter image description here

This approach uses the spherical property of the object. There's a relationship between the point's normal and it's normalized position: when the point normal faces outward it's closer to the normalized position of that point.

enter image description here

Replacing the Diffuse shader Node with a Translucent shader in this .blend also gives interesting results.

  • $\begingroup$ Very clever! I love it! $\endgroup$
    – ajwood
    Nov 22 '15 at 15:57

You can use the pointiness output of the Geometry node to get an approximate cavity map. You will need a ColorRamp node to adjust the range, so that it fits your model.

Then use that as a mix factor, or mask for the rest of your shader.

cycles material nodes

  • $\begingroup$ Good idea.. doesn't work for my model though (see my edit for my .blend). I can imagine something like "distance from convex hull?" $\endgroup$
    – ajwood
    Nov 21 '15 at 2:41
  • $\begingroup$ So dirty vertex colors is not an option? Is that because it is a bulk operation? $\endgroup$
    – VRM
    Nov 21 '15 at 3:02
  • $\begingroup$ Dirty vertex colours might be OK actually, as long as it can be completely procedural. I have a pile of different brain models, so I'd like to be able to script this effect. $\endgroup$
    – ajwood
    Nov 21 '15 at 19:53

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