Hi PaQ, in some cases you may be seeing little teeny tiny micro bumps in the surface.

But in other cases you're probably seeing various kinds of polygon shading artifacts.

Keep in mind that shading a polygon in real time can take some shortcuts and result in various artifacts that are just basically part of the rendering process.

Mach banding is one fairly common problem: http://en.wikipedia.org/wiki/Mach_bands

I mean remember that if there were not tricks involved in rendering in general (not just for real time even) you would only see flat faceted objects all the time because polygons are not actually smooth, there are tricks involved to make them sort of appear as if they were smooth.

If you use more polygons, then the polygons will come closer and closer to the actual curved surface and those kinds of artifacts get reduced more and more.

- Michael