Geneva Wheel Mechanism:
You check out the animated versions here:
The new(-ish) pointiness attribute in cycles opened up a world of possibilities for a variety of materials, but I’ve been focusing on using it for different types of processed metal.
When a hard metal (usually a steel alloy) is first machined, and its surface is chemically treated, it appears very uniform. What makes it different from most other materials is the way it wears out. Assuming it’s not a tool that is subjected to a hard work environment (like wrenches, pliers, cutters, shears, etc.), then geometrically, very little deformation occurs. I have a pair of 50-year-old calipers that barely have a dent on them. So you have to “express” the wear using almost solely the way the surface responds to light. This holds true even for scratches – the vast majority of them aren’t deep enough to warrant deforming the mesh.
So you’re left with (in broad strokes):
Variance in reflectivity – recently abraded areas will be shinier.
Oxidation – if a surface remains untouched for a long time it becomes more matte (we’re assuming this is a stainless alloy).
Surface scratches – very thin lines crisscrossing the surface in all directions. Steel is very vulnerable to visible scratches.
Anisotropic behavior – this is the result of the method of fabrication, and some of the time it’s very subtle.
(I’m omitting finderprints and dust since these will effect all materials.)
The pointiness attribute lets you automate edge effects, and this is especially useful here. Edges, on any object, will wear out faster when handled. However, when you’re dealing with steel, even a sharp edge almost doesn’t deform, so once again, only the way it responds to light changes.
This is far from being an example of a perfect machined metal shader, I’m always working on variations and trying different methods. But it’s gradually getting better.
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