Simulating Edge Wear using Inverse Ambient Occlusion.
WHAT IS INVERSE AMBIENT OCCLUSION
The Inverse Ambient Occlusion setting was introduced in Cinema 4D R18 as a way of quickly simulating SSS (Sub-Surface Scattering) and Edge Wear.
Standard Ambient Occlusion will cast rays outward, creating shallow shadows on contact surfaces.
Inverse AO will cast rays inward, resulting in fake, but fast-rendering, SSS.
Inverting the normals when calculating AO provides a mask of the bare surfaces; allowing the user to add layers of worn textures and create custom Edge Wear on any given object.