Sweep 2 rail issue

rudder.3dm (2.8 MB)
Creating a surface from this should be simple: sweep the ellipses along the orange curves. However, if I do that one end (maybe both) come out wonky and I can’t see why. If I include the blue curves and do a curve network, I get a usable though overly complex surface. Using Rhino 5 latest update.

Hi Tone - I think just give it fewer, and evenly spaced, shape/section curves:


It looks to me like the smallest curve in your set on the right in my image, by the pointy end, is maybe the culprit - it does not sit right in the progression - if you include it, use History with the sweep and scale that curve vertically -




Your curves make this really difficult. With an asymmetric form like this, I would handle it with two surfaces. Then point edited to best approximate your curves. Having a smooth attractive form is far more important than accuracy to the input curves.

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Indeed. He could just take a sphere and sculpt it via the CPs, like modeling a pebble.

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Yeah, I’m aware there are several ways of getting this shape (Lagom). I needed it to follow the blue lines reasonably close (Pascal and Stratosfear) and was surprised/annoyed when this simple approach made such a dogs dinner of it. Oh well, thanks for the input folks. Onward and upward.

@Stratosfear @Lagom

For sweep2, or actually other surface making tools,
Is there a tip on how to arrange the curves and also what to be careful of when point editing?

When rail curves are not in a plane, I find myself doing trimming and other ways to remove non tangent surfaces created…

making sure two points of each curve at the intersection doesn’t seem to make the surface created is tangent.

Not always true depending on the application.

I should have prefaced that with, curves that make surface creation difficult.

Easily done with sculpting a sphere ; )