Sweep rules and overcoming errors

Is there any clear, consolidated place that explains Sweep rules? How do I know if a spine is too curvy?

In practice, I’m trying to make this Daft Punk helmet model in a similar process as the bike helmet tutorial. But I want to sweep the front overhead shape of it, versus revolve.

I tried sweeping the full curve of the helmet, then I tried breaking the spine and only sweeping part of it and got different errors. Images follow. (Note that I copied and moved the full spine curve up to save it, but for simplicity took a screenshot in that state.)

And for search help, the errors are “Swept body has an invalid contact between two of its faces, edges, or vertices,” and “Swept body has self intersection in at least one of its geometries.”

How can I sweep this? And also, is there a better method to make this helmet model?

Edit: ugh, seriously? “New users can only put one image in a post.” Okay, one image isn’t included.

Same question.


I have the same problem with a rounded spine, though when I tried with two sharply intersecting spine it mostly worked.

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Unfortunately there is no way to tell without trying. This is a typical prblem in every CAD system, and it’s really hard to give any meaningful error feedback on this.

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Can you please help further?

Pretend I have no idea what causes these errors and therefore no idea how to move forward. Is Sweep just useless?

Also, please let me know if there’s another way you would try to construct the helmet in my question. It doesn’t have radial symmetry, so that’s why I tried to sweep versus revolve.



i would probably approach this with the loft tool instead of sweeping. In your case, the inner surfaces (the ones generated by the line) most likely causing the sef intersection, based on the screenshot you posted.

Okay I’ll give Loft a try but I don’t think it’s right here. Maybe I’ll see something else when I try again.

As before, as a beginner user it would be a great help—and make me interested in continuing to use/buy Shapr3D—if you could lay out the rules for Sweep.

I don’t know what angles work or don’t. I don’t know what those errors really mean. Explaining/documenting error messages and how to move past them seems more important than just a one-off forum answer. Please point me to any of your docs that fully explain this if I missed them.

Finally, if the problem is that something folds in on itself, and internally has problems, is there a tool that only cares about the surface?


Is there a way to distort an object by controlling Scale only on selected axes? Or another way?

While I’d like to learn about Sweep, I might have a work-around for this model by Revolving the side perspective (pictured) 90 degrees twice, and then crushing the sides in so the object is taller than it is wide.


I have done hundreds of sweeps without difficulty. Experimentation, starting simple, will give you the confidence you seem to lack. A better approach than reading some possibly limiting guidelines.