Pascal and Chuck: Many thanks for the feedback. (You do know it’s a weekend, right!?!?!) 
Yes, Pascal’s method works. Thanks!!! Chuck, did you find the tiny edge using the TestRemoveNakedMicroLoops command, or some other way? (btw: WinRhino sr7 does not support this test command, nor does the current version of MacRhino. Downloading sr8 now for WinRhino and will try it and get back to you if it does not work as described).
Unfortunately, I can’t recreate the problem that caused this problem using Sweep2 methods, but here are a few recalled details of how I originally constructed this: The piece shown is a segment of a larger piece constructed in MacRhino. The Sweep2 curves were extracted from larger surfaces (using DuplicateEdge and InterpcrvOnSrf with snaps used). Curiously, one of the three curved rails shows up as six curve segments (which you may have noticed). Huh? Something in the process caused this to happen, since the curve definitely was not created as six segments. Not sure if this matters, but thought I would mention it.
Some questions:
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Curve Segments: In situations where a continuous curve is desired from segments, I’ve noticed that Join does not create one curve, but rather a polycurve with multiple segments (and one has to “What” the Joined curves to determine this). While I understand this behavior it is not desired, since generally one wants one curve; not segments. The only method I know of in Rhino to “fuse” all the segments together is to Join them, then Rebuild the curve. Is there a better way?
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(On a philosophical note, some might reasonably conclude that the term “Join” is misleading in Rhino. Intuitively, Join implies a type of “fusion” into a larger whole, which exploding alone can not undo—one must cut apart the result since the physical state has changed (as in welding or gluing in the real world). In Rhino, if the result of any action creates a “Poly-Anything”, the words “Combine” or “Assemble” seem more appropriate and less confusing).
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Curve vs Surface Edge: When building mating surfaces (using Sweep2, and other methods) one gets the choice after the first surface is built to either use the Curve or the Surface edge. (Intuitively, the surface edge seems a better option to ensure watertight conditions, but inquiring minds, and all that…) Does it matter which is picked?
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Micro-Edges?: Possibly related to the mysterious generation of micro-edges, a long-standing frustration (perhaps due to my ignorance) is that it seems very difficult (impossible?) to determine if curve segments “actually” have coincident control points, even though they may appear continuous. And if I hazard a guess, I “think” these segments can even be joined if not coincident (but within tolerances), and even rebuilt into one curve. Either of which may generate micro-edges? Just a guess here…
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What is very much desired is the ability to select only one curve for any conditions where segments appear continuous. Then issue a command (something like “Select Adjoining” or “Select Continuous”)—this would then only select curves with genuine coincident control points. By visually seeing a break in the selected curves, this would allow one to correct any conditions where a curve appeared continuous, but the control points were actually not. (This problem seems to happen more often than you might think while working in Rhino, for reasons, I don’t fully understand. Then again, I work with some pretty odd geometry and might be all thumbs!).
Consider this a kind of “Naked Edge” test, not for surfaces, but for curves. I’ve seen this function in PowerCADD and it’s a life-saver. Is there such a thing in Rhino? If not, I submit this as a very strongly desired Feature Request since it might help with this micro-edge problem and a number of other related errors, such as filleting issues.
Thanks again for the help!
~Dave
