Surface created from Project has naked edge

I am new to Rhino 3D & I am trying to design a pair of glasses. I have been following a tutorial on DigitalTutors & near the beginning they suggest that you project the curve to a sphere then trim. I can do this no problem but what I am finding is there are a couple of naked edges which if left cause me problems for the rest of the design; yep I have learned the hard way to check for naked edges from the beginning. The naked edges on my surface always seem to be around the lower part of the bridge which is the original diagram was not a separate curve. I have attached the file for information.

Naked Edge…2.3dm (381.8 KB)

I have run through a number of different tutorials online, including the posts here, but can’t find anything that covers this particular problem. I have tried the following:

  • Project/Pull to the Lens then Split, or Trim, the surface pretty much always ends up with the same naked edge.
  • ProjectToCPlan to make sure the curve is planar (hope that is the right term) to make sure it is flat before projecting
  • Redrew original curves (several times) to make sure I hadn’t done anything silly and joined
  • Untrim and then Trim the cut out surgace again, as per one of your posts
  • Untrim the original Sphere surface, Retrim and ShrinkTrimmedSrf just in case there was some dodge point action going on
  • Created a new Sphere template in case there was a problem with the one I had been given that was “cutting” up my surface when trimming. Ok this is probably not even possible but had to given everything I could think of a try. :smirk:
  • To fix the points using Join Edge but it tells me there is no overlapping intervals so doesn’t work.
  • Patch but this just ends up with some really odd shapes but this might just me

I have a feeling that I am going to kick myself when I find out what the problem is… Any help will be much appreciated. Hope I have posted this in correct format as followed Markdown tutorial but format doesn’t seem to be showing correctly.

Thanks Laura


It’s very simple problem to fix. You need to rotate the sphere so it’s seam is no longer on the trimmed lense.

@Stratosfear LOL, thanks that does resolve the naked edge that you highlighted in your picture. I do though have another silly question, The two naked edges/points at the end of the frame are still there, triple checked and curve was not anywhere near a seam on Sphere. Is this normal as I would have thought I would have ended with no naked edges fixing this problem? Or is this something I would fix later. Thanks


All single surfaces will have edges (naked). They are only a concern when dealing with closed solid polysurfaces. The naked edge at the bridge is the result of the break in the tangency continuity of the trim curve. It should not be a concern as once that surface is mirror and joined. That naked edge should disappear. Your trim curve could be simplified and checked for tangency across the bridge. To ensure all subsequent surfaces flow together (have tangency continuity) across the bridge.

Thank you so much. Now I best go & check the tangency. :slight_smile:

Thanks a lot stratos. I would have ran into this problem and never would have thought the seam affected a project.

So, I would imagine other commands that would affected by seam are unrollsfc, what about Boolean union operations such as booleaning the frames that were made with seam adjusted, and booleaning it in a place on the sphere where the seam is at.

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Happy to help. I use Adjust close surface seam, all the time. For all the reasons you listed and their ability to bomb fillets.

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Hmm, bombing fillets too. Cool. Is there anything else that you can recall that seams mess up or can cause problems down the line. Also, are there any situations that you can recall where instead of getting in the way, that the proper use or knowledge of seam placement can add additional functionality or features that can add to seams that were not payed attention too. So basically, if you didn’t move it, it wouldn’t really cause a problem, but in a certain command, a seam can add functionaility options previously not known, or rarily known.

I think I am going to have to do a little writeup or tutorial on them, with some flowcharts to be on my way to completely understanding seams and I thank you. Also, can you get a little more specific in what places a seam on a surface to filleted would affect a fillet or good search terms/threads/links if you had any in your bookmarks or something.

The kind of additional functionaility I am referring to is something similar to what I am working on for Rotating, Cplanes, and Views. Basically, to me cplanes were quite confusing before as was rotating and orienting. But using cplanes in rotation aids, and cplanes in rotation and orientation aids to view, and combinations of them can make getting your objects where you want in a easier to understand and see way to do it.
See what I mean? So instead of using rotate 3d, you can use a cplane, set to view to turn a complicated rotate 3d into a more easily navigated 2d rotation and adjust your cplane visually in perspective view.(well not that easy, but with macros you can create the cplanes grid using lines, set it to a layer with colors and arrows for coordinate axes, use a center point on the created cplane grid to move, rotate the cplane, etc… The options are endless and I am working on some buttons to help out.

The one macro which first got me into this is the rotate and orient by two points from perspective view. So, you have two objects. You turn object 1 roughly or exactly (can be slightly changed later) in perspective view how you want object to be, when you place object on or near it. Then set cplane to view, and make a short line for the orient points command, then go back to world top, and rotate your camera or view how you would like object to be orientated and rotated in relation to the position chosen in the first step. Then set cplane to view, and make the 2d line where you want the lines to match and line up. Then run orient points. So you essentially kinda save a lot of fussin with moving, rotating and orientating, or can at least get it pretty closely roughly where it will be permanent!

But learning cplanes, and rotating them, moving origins, and being able to see up to 5 cplanes, update their grid and origin where you want in perpective, then update the actual cplane, then continue on modeling etc will definitely help out in meausuring, building coordinates and lines in specific angles easier, give you good angles of construction plane to make more difficult angled offsets etc…

So that’s one of the tutorial, toolbar, ideas, understanding, and making things like awkward angles, awkward point picking, faster rotations, and faster object placement a little easier than 1 command has to offer.

So, I was just asking if you knew of any kind of tips or things like the above mentioned that seam knowedge can aid in additional functionality?