Newbie Sweep1/2 question

Original photo:

First attempt to model the same chair cushion

The next step is to introduce a groove on the seams (illustrated by the red Pipe)

The groove/fold/crease created by a Pipe with a BooleanDiff produces edges way too sharp, and I plan to Sweep1 or Sweep2 a smoother profile:

Question1: how do I position a custom Sweep profile (cross section curves) to run along the rail/edge and keep it somewhat tangent to both connecting surfaces?

Question 2: Is there another simpler way to make a smooth groove in a solid?

Thank you,


try with edge softening instead of modifying the geometry.

If you need to fillet, then Split away the fillet part with a pipe and put a “helper target surface” in the middle of the two fillets, then blend the fillets towards the helper surface…

// Rolf

RIL, thank you and please bear with a newbie here.

I would absolutely love to have an edge “in the middle of the two fillets” for the purpose of unwrapping the geometry later along the new seams.

How do I create a “helper target surface” in the middle after I split the surfaces with a Pipe? I can FilletEdge and BlendSrf parts later.

Thanks, Diego.

If you mean shutlining or any other rendering tricks for edge softening, I cannot use them - I use V-Ray plugin in Rhino for the final renders.


Try something like this:

Wider blend looks better (tangent, tangent in this picture)

// Rolf

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Rolf, this is the solution I was looking for - the crease/fold looks perfect. I understand the concept on the 2D plane, thank you for the illustration.

Now I just need to figure out in which direction to extrude and move the HelperSrf for the cushion as a whole in the 3D world. Should I do one side at a time? And then manually fix the geometry at the corners later?

Thanks again for your time and patience.


Hi Arsen - if you extrude the curve before making the pipe & trimming, i.e. while the curve still has the surface under it, you can use the Fin command (Extrude curve normal to surface) to set what will be a useful direction in many cases.


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Thank you, Pascal, this is a great hint - Fin is fantastic with creating a normal extrusion to a surface.

What would you recommend with the corners of my cube (cushion) after I complete the sides? Manual blending for all?

Hi Arsen - I think I’d trim those surfaces with a BlendCrv and then carry on with Fin


BTW, a cheap way out is to FilletSrf to a fin, then trim



Thank you, Pascal - I am working on it.

Hi Arsen,

Instead of actually modelling the creases, you can als try and see if the Shutlining feature works for you.


You can extract the resulting render mesh (ExtractRenderMesh) - V-Ray should probably be able to use that…