Creating interference

[buggs_moran]

So we have seen lots of ways to have things disappear when we don't want them to. What if I wanted to MAKE a part of a texture disappear. In other words, I have a rotating ring mesh, but I only want half of it to show. Can I cancel the rest by putting another mesh around it to "cancel" it out? I thought an Emissive true trick might work, but I wanted to pose the question first. I need the other half to be eliminated from view, essentially transparent.

[GlobeMaker]

When a mesh has normals pointing toward you it is visible.
When the normal points away, the mesh is transparent. Selden
used that on one version of his graticules.