Dimension variable radii

Hello everyone, I’m new here. If I draw a compound curve with the poly line tool the end result is a smooth undulating snaking line. The radii of each undulation is inconsistent. For lack of a better term I call it a variable radii. My problem is I don’t know how to quantify or describe these shapes with numbers. These shapes need to be described in a 2D drawing accompanied by some kind of dimension or numerical designation.
Thanks in advance for any clues or direction.

Hi Geoff,
This can be a challenge.
One option is to convert the curve to arc and dimension the arc like typically do, with center location & include angle.

See the attached model.
I am sure there are other ways, but this idea may lead you to others.

Mary Fugier
McNeel Technical Support

Dimensioning a NURBS Curve
0. Copy curve and hide.

  1. Use CONVERT to convert NURBS curve to arcs
  2. EXPLODE into Arc
  3. Make ends with CRVEND
  4. Mark center at with Points
  5. Angular dimension arcs
  6. WHAT command on Centers for x,y,z coordinate
  7. Mark centers with Leaders

dimensioning NURBS curve.3dm (145.8 KB)

If you are creating drawings from which something will be built, one thing that’s often done is to simply print the curve on a grid, similar to the Rhino grid visible in Mary’s post. the person then recreates the grid and can break the curve down to a square by square sketch. Not perfectly accurate but as good as any analog method.

Nick, Thanks. Yes, This is a drawing for a metal spinning. This is a technique my industrial designer friend said the old school engineers used. It makes sense and is simple enough. I wanted to make sure there wasn’t some Rhino command that made it quick and easy. Cheers.

Thanks for the reply Mary. I’ll try it and show it to the machinist.