Is it possible to ʼunrollʼ a 3D surface into a flat 2D pattern in Rhino?

Short Answer

Yes — in Rhino 3D, you can unroll certain 3D surfaces into a flat 2D pattern using UnrollSrf, which is the standard professional method for developable geometry like cones, cylinders, and ruled surfaces. It works best when the surface has no double curvature. Complex freeform surfaces usually need approximation instead.

What You Need to Know Before

Warning: UnrollSrf only works reliably on developable or nearly developable surfaces. If your surface has compound curvature, Rhino may fail, distort the result, or force you to use a different workflow such as Smash or Squish with acceptable deformation.

How to Do It

• Command: UnrollSrf

• Shortcut: UnrollSrf

• Quick Steps:

  1. In the Command line, type UnrollSrf, or go to Surface > Flatten Developable Surface > Unroll Developable Surface.
  2. Select the surface or polysurface you want to flatten, then press Enter.
  3. In the command options, set Explode=No if you want joined output, optionally use Labels=Yes, then place the flat result in the 2d view.

Variables & Settings

• Key Setting: Explode

  Controls whether Rhino outputs the unrolled result as separate faces or keeps it joined when possible. For fabrication layouts, keeping Explode=No is usually cleaner unless you need individual panels.

Why it Fails

• Cause 1 (Geometry): The surface is not developable and contains double curvature, so UnrollSrf cannot flatten it accurately.
• Cause 2 (layers/Locks): The source object or related geometry is on a locked layer, preventing selection or output placement as expected.
• Cause 3 (Command/Logic): You are using UnrollSrf on freeform shapes that should be processed with Squish or Smash instead.

Quick Fix & Best Practice

• Quick Fix: Run CurvatureAnalysis or inspect the shape first; if the surface is doubly curved, switch from UnrollSrf to Squish for an approximate flat pattern.
• Manager’s Verdict: Use UnrollSrf for sheet metal, plate work, cones, and other developable fabrication surfaces. Avoid it for organic or heavily sculpted forms unless distortion is acceptable.

FAQ

Can Rhino unroll a polysurface?
Yes, if the polysurface is made of developable faces.

What if UnrollSrf does not work?
Use Squish or Smash for approximate flattening.

Does unrolling keep hole and edge geometry?
Yes, Rhino can unroll associated trims and boundaries with the surface.

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