Hi Rich,

> I know MoI wont do this natively but does anyone know how this could be done in Rhino?

Rhino does have a couple of different unwrapping commands - one called UnrollSrf and another one called Smash.

The entire process of exactly unrolling a curved surface is fairly complex though and whether you can do it can depend on the shape of what you've constructed.

For example say you draw a sphere and then want to unwrap that into a flat pattern - the problem is that the sphere is not a "developable surface" - there is no way to unwrap in in such a way that does not involve stretching or compressing in the 2D flattened result.

Rhino's UnrollSrf command is only set up to work with developable surfaces - these are surfaces that are straight in one direction like a cylinder, extrusion, or cone type shape and that flat direction is then possible to place exactly down onto a 2D outline.

Rhino's "Smash" command I believe is set up to allow a type of unwrap of a non-developable surface and will show you something about the amount of stretching involved in the result. If there is very much stretching and you don't have a stretchy material then it would not work though.

So there are some various caveats with those processes depending on the particular shape and way you have constructed your surface.

Another way that can be less complex is to convert your model into a triangle polygon mesh in OBJ format and then bring that into Lamina Design which works on unwrapping polygon geometry. Check out some of these other threads for some mentions of other software that might work for you too:
http://moi3d.com/forum/messages.php?webtag=MOI&msg=5550.1
http://moi3d.com/forum/messages.php?webtag=MOI&msg=5463.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=3042.8

- Michael