Strange looking artefact in model

Hi all!

Kinda new to Rhino and to the forum here.
Currently trying out the evaluation version on Windows under Parallels Desktop 12 on a Macbook Pro. I know I know, … not ideal. I’m waiting for my Windows laptop laptop to arrive.

I’m mentioning all of this because I’m facing a strange artefact in my model and was wondering how that would come. Any ideas?
Hardware or rather a modelling issue?

Many thanks for your help guys.

CocktailRing.3dm (1.4 MB)

You have a lot of bad surfaces that have knots and control points that are stacked (or so close together that they behave as stacked)
The stacked knots in the surfaces lead to bad boundaries where the surfaces are trimmed against each.

Your best bet is to start over with the idea of making cleaner surfaces without stacked control points. Unfortunately Rhino doesn’t have any good tools for detecting and avoiding stacked or too close surface control structures. Sometimes the only way to tell is to window select what looks like one control point and discover there is more than one there.

Thanks for taking a look at this Jim.
As a roundup what does this mean in human newbie language? That where my points use to snap together, they aren’t snapped together? Correct?

Is there a way to avoid this when I start over? Because I’m just following along a tutorial from Plural creative (use to be digital tutors) to make a cocktail ring since I’m new to Rhino.

Many thanks again.

The problem is that because Rhino has no way of detecting these types of bad geometry there may be no easy way to determine how this bad geometry was created. I doubt Osnaps had anything to do with it, but it is possible.

My best guess is that the stacked knots first appeared in the main surfaces that make up most of the outside of the ring. Then you used some operation that created the inner surfaces by offsetting those outer surfaces. The offset operation transferred and magnified the error to the inner surfaces where you then noticed the problem.

So the question is how did you make those outer surfaces?

Hi Pieter - that one surface has stacked/coincident control points along the vertical edge there that does not shade correctly. Use RemoveMultiKnot to clean up, but it might be good to see the curves that generated the surface - I think this was a Sweep2, right?


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