Why cannot I offset this shape 1.0 mm towards outside?

[junehe]

Why cannot I offset this shape 1.0 mm towards outside? I have attached the original dwg file here. Thank you very much! cannot offset.dwg

[MSasu]

Is quite strange, at least for me, that the otside offseting seems to be somehow disabled. There were not self-intersections on your entity. However, if you explode the spline it will be possible to offset it as desired, although I'm not sure if this is feasible for you.

[Dana W]

In AutoCad 2015, one can see that it is a "control vertices" spline, not sure if that exists in 2013. The vertices alternate inside and outside of the "line" in a number of very tight places, indicating opposing arcs, so the calculations in the drawing database might be showing AutoCad places where the "real line" does recurve drastically in some very tiny places and will create a self intersecting path if offset. You can see these places if you click the edit handle and change it to a FIT Spline.

 

One way to get it to offset is to change it via pedit, to a polyline. This, of course results in about 600 waddzillion vertices in the pline, but it will offset then, and retain its smooth shape. This massive count of vertices will remain, if changed back to a spline via pedit.

[lrm]

junehe, I tried using splinedit on the spline several times and AutoCAD crashed. I was successful in creating the final spline you want by first creating an offset spline 1mm inside the spline and then creating an offset spline 2mm offset to the outside of that spline. It was necessary to create the final desired spline with 5 pieces, each with many CVs but not as bad as a polyline approximation. BTW, Offset will create self-intersecting splines in some cases but not always.

 

P.S. MSasu, I like your Fibonacci icon!

[junehe]

Thanks Irm! I tried your method and it worked! I just need to connect these 5 pieces together then. Better than trace all over again! Thank you!

[lrm]

junehe, You are welcome. I find that a good problem solving strategy to use when you are stuck it to do the opposite of what you are trying. For example, if you are using the top for a solution with no luck try using the bottom, if you are combining components and cannot find a solution try using individual components. Sometimes it is helpful to move a problem to a different domain. If an analytic solution does't work try a trial and error approach which may yield a satisfactory solution.