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I'm working on a geology surface model, and I'm trying to find an automated way to identify cracks, rifts or crevasses. One way I thought of is to identify faces with normals crossing at a certain opposed angle (+- 180°). Of course the value of this angle is important, as is the distance threshold (ultimately, most normals are probably crossing each other).

Does anyone have an idea how to do that? I suppose it would need some scripting as it's a quite specific problem...

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You could try hooking up a Pointiness node to a ColorRamp. If you're working in the experimental 2.8, the Ambient Occlusion node does exactly what you're after, and you can ramp it, as well. In addition, if you check the 'inside' box, you'll see where are your strongest ridges and outcrops are.

Since it is an experimental version, I'd suggest saving a copy of your model when you're finished modeling it, and uploading the copy into 2.8 just to bake out the AO shader as a map to use in your original.

You can also bake out the AO directly in 2.79, but this requires world setting and futzing around with lights, plus your results are usually very noisy under 2k resolution. The shader in 2.8 is both simpler and faster, plus it looks much cleaner. If you want to go for the 2.79 option, the wiki actually has a good tutorial on it, and you can find it all over YouTube.

Please Take Notice: Currently, the Ambient Occlusion node 2.8 only works in Cycles, not Eevee. As you start in Eevee by default, you'll need to switch your render engine, now located under the render settings tab.

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  • $\begingroup$ In 2.79, I found an Ambient Occlusion checker in the Shadow Properties tab (only in Cycles, as you said). Changing the strength, it really does identify the cracks. I'll try the node solution too. $\endgroup$ – gvanhavre Oct 16 '18 at 22:48

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