Problem Offsetting Surface


I have been trying to execute a simple offset command but I facing a few issues. I am fairly new to rhino and just trying it out.The offset seems really distorted. As I keep increasing the offset distance, the offset surface get really distorted.

Thank you and the attachment is below.

Trial.igs (190.1 KB)

Offset appears to be working properly with your file.

Offset curved surfaces can sometimes result in surprising shapes. The curvature of an offset surface will be different than the original surface. Creases will develop if the offset distance is large enough. The shape of an offset surface will be different than a scaled version of the original surface. This behavior is how the geometry works, and is not due to any problems with Rhino.

If you still have questions about your results post a file with the offset surface and describe what the specific problem is.

Also, why did you upload an .igs file rather than a .3dm file?


Thank you and I think I understand. I was experimenting and I wanted an offset that has similar accuracy to the original surface. And as to why I have an .igs file, I have been working with scan data and used geomagic deisgn to produce this surface. I was experimenting with the offset and just wanted to learn.

So, these distortions when I offset are normal?


Hello - yes, I’d say that is expected - if the offset distance to the inside of a bend is greater than the surface radius there, the result will cross itself. You can use the Curvature command on the input to find at least a reasonably accurate minimum offset distance - check in the area of the tightest bend, MarkCurtvature=Yes and measure the radius of the smallest circle. Or use the command line output from this command to find the radius at that point:

"Maximum principal curvature: 0.0368056 "

Radius = 1/curvature = 21.4657


I see, this was really helpful. Thank you so much.