Rounded top surface. C

Working on a spare part to a toilet flush knob. Aiming to make the top surface rounded constrained by the elipse like shaped top surface and the spline curve. The slab is 3mm and the mid point of the spline curve is 3mm above the elipse like shaped slab.

I can’t figure out how to proceed. Hints are welcome.

— Magnus

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Here you go.


That is a neat trick. Thanks. It is almost as I would like it but unfortunately this will result in the slab to not be equally sized along the edge of the elipse like boundary. Would like to loft/lift the surface at the midpoint but constrained at the edges

All roads lead to shapr 3d

All roads performed by shapr 3d


I would suggest using loft with guides.
Here is what you could get, with nice surface tension and no visible artefact.

First, add a small radius on the sharp vertical edges. I used 0.1mm radius, but ensure the circle arc is tangent to the shape.

Then, loft separately:

  • half of the small rounded portion at the edge, with 2 perpendicular cross sections and 2 guides
  • half of the main body with 3 parallels cross sections and 3 guides

and complete the shape by mirroring as needed.
This is the best way I know to get artefact free shapes like yours.

If you try to loft only 1/4 of the shape and mirror, you will end with shape artefact, as in the picture below : left shape is as explained, right shape is 1/4 of the shape and mirror.

I included the .shapr project used in the video.
rounded shape.shapr (42.4 KB)


Thank you - This was exactly what i wanted to do. The video was key for me understanding the steps.

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