This image, (not done in POV!!) is close to what I am trying to learn how 
to achieve in POV, or even in a POVMan shader.

The top grid is spherical mapped (2x4) onto a sphere as a displacement.
The grime is derived from the disp map combined with a high-pass filtered 
image of the surface's normals post displacement.
i.e. it is 2 pass. The grime map is used to blend between 2 maps, a clean 
copper and an oxidized one.

Would anyone like to take the displacement map and try to do one of these 
standard grime balls, using POV or MPOV?

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