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Problem with ellipses


I drew two concentric ellipses on two different plans and made a surface with multi-sections along with a guide but as you see three irregular lines are created on the face. I did repeat the operation a few times but the result was the same, though the distances between the lines are changed. What is the reason and how I can correct it?

Thank you
Hi Mans,

Have you tried with Blend feature? Remove the line you created between the 2 ellipses. and just connect them with a blend, I think that should work. ** Also the "lines" you see on the screen are just showing how the surface is divided in patches.


No, I didn't use blend and tried to create the shape with multi-sections.

You are right. I think blending is a proper option I will use it after some other exercises.

However, the patches show that the operation had been imperfect

Thank you very much :)


Super Moderator
I just used a guide line
I don't think using the Line as a Guide will help with only 2 sections. But it won't hurt either.

I would use the two end points of the lines as Closing Points to try to improve the patchwork of the swept surface. I would also make sure the Coupling type is set to RATIO (but that's probably the default).

Since this is a learning exercise, I suggest you try different options and see what happens.

Multi-Section Surface is the most obvious solution to this exercise. I'm not that familiar with Blend, but I guess that's another solution. You could also try a Sweep surface by sweeping the line through the two ellipses (guides).


I will use your good recommendations as well. I think sweep is another option for this shaping but I wanted to understand how I can create the shape with multi-sections intact and without any fault. As you guided, in the next time I will transfer the closing points of the ellipses to the points of the line. Probably, it will resolve the problem.

Thank you :)


New member
Guys... the problem is that you have vertex points on your curves. Every vertex creates a line which divides your surface to patches. So you can either set your position tolerance to a minimum (doesn't matter if it's a Blend, MSS or Sweep) so the surface will have a small deviation from the curve but it will be smoother - OR you can use Curve Smooth on your guide to smooth it with an operation. Instead of using the Ratio option you can also use one of the profiles as a Spine - this will cause that the surface will be perpendicular to that Spine in it's every point.