UnrollSrf UnrollUV UnrolSrfOld Smash SmashOld (FlowAlongSrf)


Can someone enlighten us on the various unroll / smash commands and what to expect?

UnrollSrf = best option for unrolling (near to) developable surfaces?

UnrollSrfOld = ?

UnrollSrfUV = depricated? but no replacement…

How do Smash and SmashOld relate to this?

And what about Squish?

My take is that all these commands attempt to create a flat version of a Brep, best to be used depending on the input and intended use. Is there a comprehensive list of the use of these various commands?

Alarming to me is the fact that there is (apparently) no longer a command comparable to UnrollSrfUV where the parameterization of the input surface is preserved. This breaks a powerful workflow to unroll a surface with UV’s preserved as a means to create a flat canvas to model on the 3D surface. The UnrollSrfUV command in combination with FlowAlongSrf seems no longer possible in V6. Also see the help on UnrollSrfUV for V5

V5 Flatten curves and surfaces

V6 Flatten curves and surfaces

It seems Squish and SquickBack are intended to mimic the unrollSrfUv -> FlowAlongSrf workflow yet a single first test revealed it to lack crucial functionality the previous workflow had:

  • SquickBack is limited to curves and points and even only on a 2-D pattern
  • SquickBack is not linked to the input geometry so moving/editing the input will break usability
  • SquickBack cannot be applied to other 3D surfaces but is limited to the single input only.
  • SquickBack does not allow for tweaks in the parameterization (eg moving controlpoints in 2D slightly to position the flowed geometry on the 3D surface)

Please bring back UnrollSrfUV or parameterize the Squish result

Side note: FlattenSrf Command does not flatten a surface! it creates outline curves, what is it’s intended use and why is it named FlattenSrf?

To summarize:
Please provide a comprehensive list of flattening tools
please make sure such valuable workflow as unrollSrfUv -> FlowAlongSrf is not depricated.


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Hi Willem -

I think:

Yes - fairly strict about developability.

I believe this is offciially UnrollSrfUV now

This is an older (V4) and generally less accurate in some cases, I guess, UnrollSrf that had the advantage of maintaining the UVs of the input on the output - this makes it useful for creating base surfaces for FlowAlondSrf - some users were left hanging when this ability was removed in UnrollSrf so the older one was resuscitated as UnrollSrfUV.

Smash is the liberal version of UnrollSrf - it does not care if the surface is developable, it will make something regardless.

Different thing - it is designed to unroll somewhat double curved surfaces - like steel plates for a ship hull for example. It has some settings for taking into account stretch and compression. It works off of the render mesh of the object (and works on meshes).


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Hi Pascal,

But it’s not in V6…or did I miss something.

You’re right… @lowell do you know if UnrollSrfUV is still meant to be in the mix for V6?


UnrollSrfUV used to be named SmashOld, and was renamed in V5.
It looks to me like that renaming happened after code was split to V6, and the renaming never happened in V6 so that command is still named SmashOld in V6 and should be renamed to UnrollSrfUV there too.
I’m reconstructing that explanation from what I see in the code and comments, not from memory of having done or not done it (which I undoubtedly did or didn’t).
Well, Something like that anyway. See RH-17530 and RH-35526.


Great, thanks. & Thanks Willem, for pointing it out.


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Hi I need to draw the top and bottom boundaries of a balustrade
I tried unrolling the surface and the curve (Intersection between steps and vertical surface containing the balustrade), to draw in 2d the shape I’d like the balustrade to have.
There’s no a “Rerollsrf”… I read about the option UnrollSrfUV + Flowalongsrf,
but it isn’t working:
I can UnrollUV a Polysurface
The FlowalongSrf selects just one surface of the Polysurface…
How can I do?