Hi TwinSnakes,

> and we need to be able to constrain by a 3D distance.

This one is the tricky part - on a wavy surface the constraint won't be just by a direct 3D distance between points, it would be by the distance traveled while hugging the surface, kind of like the length traveled by an ant walking along the surface...

On a cube with planar surfaces, everything is a lot easier... For working with just any surface at all things get way more complicated.

On top of this I see a lot of other difficulties - there would be cases where the rigid curve would actually not completely follow along a surface to maintain its same length. Like imagine a pocketed surface like a golf ball - if you try to apply a bumper sticker to a golf ball, the sticker is not going to completely hug along the entire surface of the golf ball, it won't touch the surface when it goes over one of the dimples. So just walking along the surface directly won't really give the proper result.

Also imagine taking the bumper sticker and trying to wrap it around the eraser end of a pencil - the sticker will kind of gather up and bunch together...

It seems like a pretty difficult problem.

- Michael