Flatten double curved surface - command?

I wonder what makes the most accurate result when flattening a double curved surface.

If you look at the image you can see there is a big difference in the resulting panel.

Smash or squish or other?

It would be nice if the result could be used cutting the panel in a cnc machine.

Roy Berntsen

the results are closer than the image is showing… if the squished surface was rotated a little bit, they’d line up better.

i’ve used both commands for flattening then cutting then building and they’ve both been satisfactory… these days, i’d personally use Squish…

that said, the materials you’ll be cutting and bending have a lot to do with how well these sheets will bend into place and how accurate the cuts will be… it’s almost certainly going to require some experimentation with your materials/requirements in order to find which one is best for your situation… i don’t think there’s a concrete answer to your question, especially without knowing what the material is or how much bending is to occur.

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From the information page about Squish when it was introduced several years ago: http://wiki.mcneel.com/labs/advancedflattening

  • Smash - is a special version of UnRollSrf that does not check to see if the surface is developable. It is not recommended now that Squish is available.

  • Squish new - makes a flat pattern from a 3D non-developable (curved in two directions) surface or polygon mesh. In general, try UnRollSrf first.

Pascal commented in an earlier thread about the difference between Smash and Squish: UnrollSrf UnrollUV UnrolSrfOld Smash SmashOld (FlowAlongSrf)

In addition to the material properties which Jeff mentioned, the fabrication method used to introduce compound curvature into the metal will affect the physical “flattened” shape which corresponds to the finished item.

If metal will the metal be locally stretched by hammering or rolling on an English wheel? Or will the metal be locally shrunken? Or a combination of the two? Or will the metal be bent over a series of frames without any direct control of the deformation?


Thanks for the response. The material is a sandwich of grp and PVC core. I think I will use the squish as the result is single span surface.

Fibreglass foam sandwich panels are quite stiff and may not distort enough to produce a non-developable shape. I would highly recommend reviewing this surface and possibly re-creating it as a purely developable surface.

One way to review the surface is to create a similar purely developable surface and compare the deviation across it to the original.


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Thanks @Ncik. I wonder how I missed this plugin/command after being a yacht and boat designer for many years… I will definitely have a look at this.