Hi Peer, it will be great if this will be useful for you!

re:
> Also attached is a pdf (5 pages) illustrating my application and showing some hatching
> I did using MoI. I eagerly await hearing whether your experiment might lead in that direction.

It sure seems like it will do that for you, automatically like magic!!! :) :) :)

In your PDF the main way to convey the shaping information currently would be to generate the shaded background image to go underneath the vector outlines.

But the cross hatching should help convey that information using vectors only. Or you can still use it in combination with a shaded background image too.



re:
> Do the hatch lines follow the local geometry of the parts (like uv), or are they partially determined
> by world (xyz) coordinates? For example, what would the results look like for a coil spring (attached)?

They follow surface curvature, going in the principal curvature directions:
https://en.wikipedia.org/wiki/Principal_curvature

It's basically tracing a "Line of curvature" as described in above wikipedia page. Spacing is done in 2D projected page or screen space.

Here's what it looks like on your helix, it seems to be the right thing to do, yes? :



- Michael