Split a Revolved Surface

I'm trying to split a revolved surface so I am left with the part that is protruding from the box in the image below.

I don't understand why this is so hard! I must be missing something!

Is there a better way to create this surface?

Attachments:

3_1.gh, 17 KB

Replies to This Discussion

Permalink Reply by Ethan Gross on August 30, 2017 at 3:01pm

Hi Martyn,

It might have something to do with the seam orientation so I instead swung a half-ellipse around 2 Pi, so the seam is totally within the box. Also, I and others on this forum have had problems with splitting conics and surfaces based on conics. Too few control points???

Attachments:

3_1 b.gh, 13 KB

Permalink Reply by martyn hogg on August 30, 2017 at 3:17pm

Thanks Ethan!

Good reminder of the Shatter component too!

Permalink Reply by Joseph Oster on August 30, 2017 at 5:58pm

Good call Ethan. That revolved ellipse was a nasty surface!! NOTHING would intersect with it. Even with Ethan's fix, it's still not a "Closed Brep" so I'm surprised that 'SDiff' works. Here is a 'SrfSplit' approach, one of several intersection methods that all failed with the original 'RevSrf'. It has a test sphere in addition to the ellipse.

Attachments:

ellipse_2017Aug30a.gh, 30 KB

Permalink Reply by Joseph Oster on August 30, 2017 at 7:28pm

Simplified:

Attachments:

ellipse_2017Aug30b.gh, 23 KB

Permalink Reply by martyn hogg on August 31, 2017 at 4:11pm

thanks Joseph,

I always have issues with revolved surfaces!

Permalink Reply by Michael Pryor on August 31, 2017 at 4:13pm

Its the seams, happens often with spheres also. Even just in rhino things get weird if you say.. try and draw a curve on surface across the seam - it usually wants to go the opposite direction.

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