I’m a little taken aback by the apparent loosening of the tolerance.
First to quote the Help file on UnrollSrf
Flattens ( develops) a surface or polysurface with curvature in one direction to a planar surface.
Yet if I understand your wording correct the above statement is not true. It should read something in the line of “Flattens a surface that is about 90% flat in one direction”.
What strikes me as odd is that a tool with the purpose of flattening developable surfaces had a relative tolerance of 10%. It renders the tool useless for production purposes. I wonder what sort of requests were made to justify the loosening to such high tolerances. Those might have been for users modeling kit bags, not ship hulls. @heath Could you shed some light on this, you are an expert in (un)rolling sheet-metal and wonder if you use UnrollSrf for this and if a tolerance of 10% is acceptable.
I understand there is a need of some tolerance to allow for (nearly) 0 curvature in one direction to be met, but this needs to be an in command option. The way UnrollSrf is currently setup makes it no longer reliable to me. I will see what squish can do and otherwise I need to install V4 again just to have a (more) reliable way to unroll surfaces.
Note that many times I use UnrollSrf as a means to check the validity of a design that is to be made in sheet-metal. In some cases I script UnrollSrf so I need now to add extra double checks to validate the surface has actual 0 curvature in one direction.
Forgive my ignorance, but how is the 10% determined? The example surface clearly has a bump that is absolutely not developable, regardless of the rest of the surface being flat or not. If UnrollSrf is not able to catch such local 2-way curvature spots it fails at being a tool to unroll nearly flat surfaces.
Finally the question that is most important for now:
- How can Rhino V5 reliably only flatten surfaces that have no curvature in one direction?
- How can I check that a surface has no curvature in one direction?