Curved ribs on curved surface with draft angles

Hello and thank you for your help in advanced.

I’m creating an insole and I’m trying to add ribs on the bottom of the insole. It’s a non symetrical curved surface. If I have some lines drawn that are offsetted from that curved surface and then using those lines with the command Rib and then the option Offset=NormalToCurvePlane it will let me do the curved ribs but it doesn’t give me a draft angle option for these ribs. If I choose Offset=InCurvePlane option inside Rib command it gives me the option to add a draft angle but the ribs can’t be curved (it will intersect the curved surface of the insole but the top of the rib has to be planar).

Is there a curved rib with draft angles option or do I have to take a different aproach?


Seems like ExtrudeSrfTapered could be the key to making curved ribs in Rhino.


You could try a few things. You could flatten your insole surface, make the drafted ribs, and flow them back. Depends if the draft angle is needed specifically relative the world or to the surface.

If you have a file, I’m sure someone could help take a look at your design.

Jonathan, flattening the surface is a good idea. The direction of the ribs has to be in relation to the C plane and not the curved surface of the insole.

I’m attaching a file of the insole. The ribs go on the bottom obviously and with a height of about 2mm and a thicknes of 1.2mm with a draft angle that tapers up to that 2mm height. It’ll be some kind of grid pattern and they’ll be cut off so the ribs are about 4mm off the C plane to allow the insole to still bend.

Thank you

Surface for Ribs.3dm (302.9 KB)

Hello - can you post a file with some indication of the rib, the height and angle in there?


I had a quick look. I would take your bottom surface and use ‘SetPt’ on the surface. This will flatten it. Then draw the stuff you need in 2D, ExtrudeSrfTapered.


draftAngleMaybe.3dm (3.5 MB)

I did it with a 10 degree draft angle just to illustrate. Then you could do all your filleting afterwards too… or even better, do stuff like corners prior to flowing. I just stuck some fillets on another layer for show.

The best thing here is to ConstrainNormal=Yes when using FlowAlongSurface. You might have to flip the CPlane Z direction for that to work. That’s why the short edges angle up very severely.

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Jonathan, that is great! thank you for taking the time, I will use that technique.