Extruding a curve perpendicular to a curved surface

I would like to trim the arms of this banquette similar to the sketches attached. I can’t seem to draw on the curved surface of the back despite selecting that option for the curve tool (it drops below the surface), and additionally I do not know how to begin the extrude process.

Perhaps there is a different workflow for this operation. I had considered cage editing the top surface of the banquette arm for instance, and trim the sides with that… but I am coming up short. Any advice appreciated!

banquette_test.3dm (3.1 MB)

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ou could use the _FlowAlongSrf command and flow a trim surface created on an unrolled representation of a part of your object…

banquette_test_flow.3dm (582.6 KB)

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thank you for your answer- would you be able to break this down a bit more? I am not able to get the command to execute this operation as you have shown. I have had some success with _WireCut, though not on curved surfaces.

These designs are really basic solid forms, if you forget the sitting part / cutout. Model the basic forms with the armrests first and cutout the sitting part second. For example, the corner sofa is just a simple Sweep1 job.

I accomplished this by drawing a _Curve with the ‘On Surface’ box ticked, offsetting on both sides, > _NetworkSrf > _Trim.

I’m sure there are multiple ways that are better.

Always curious about other work flows. Thanks!


SubD with reflect on…

subd_sofa.3dm (198.1 KB)


This is very cool and I’d be interested in seeing your process. this is actually a wood banquette and thus not as rounded as you’ve depicted. Also, you’ll notice that the arms are not symmetrical which is also per the designers request. Even so, I’m alway interested in learning more about the SubD workflow.

Yes, they are simple at this stage, however not symmetrical and thus not possible with Sweep1.