How to avoid Bezier curves fragmentation? (it happens randomly)

Why bezier curves end up fragmented after some time? Sometimes they do it after exploding a group they are in, but at least this is not consistent, and it is not the case for the one I show in pic below - the one in the white shape:

I just double click the group that contains the curve so that I can select only that curve, but when I click on the curve now, it only selects a tiny part of it. This morning I could select the entire curve with a click without problems. Now I have to select all these fragments individually until I select the whole curve.

Even more striking is that I haven’t done anything with that curve between this morning and now. In fact, I just created it for investigating the cause of the problem. Also, the one in the right, works right and only difference between the two is that the one on the right has been later. Indeed that one has been manipulated more than the left one.

What’s going on?

Attached is a file with those two curves. I have manipulated the right one even a little bit more, but it still works. Maybe in a couple of hours won’t…

example formas curvas - explosion fragmentation.skp (27.1 KB)

Keep in mind that, internally, SketchUp only keeps track of Edges and Faces (Yes, I’m ignoring things that aren’t actually geometry - like layout lines, dimensions and text.

Sketchup also tries to keep a little bit of metadata (like the radius of an arc) and - mas o meno - manages to preserve such until a basic geometrical action breaks up SUs internal representation of the the collection of edges that make up the entity.

Note I haven’t (yet) mentioned Bezier Curves. At the SU internal level, it’s a collection of connected edges. There might be a metadata reference to something that is handled by an extension (like Bezier Curves), but once something inside SU breaks the existence of the collection (and it’s metadata), the extension can no longer recognize it as something it created - and hence can no longer manipulate it as a Bezier Curve.

I’m guessing that, somewhere along the way, something you asked SU to do “broke” the collection of edges forming the Bezier Curve. What might it have been? No clue. Without a complete replay of the manipulations you’ve done, there’s little hope of identifying the step that broke the curve.

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One thing (of many possible things) that could break the Bezier curve (or a circle or an arc, in a simpler case) is drawing a line that starts or ends on one of the vertices of the curve, or crossing it with a line or other geometric construction like an arc, circle or rectangle. in the same context.

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I can confirm the curve must have been crossed at some point in order to break it,or exploded. Although, it can be fixed back to a Bezier Curve using the bz context menu if needed.

I don’t know if it helps but here’s an example:

EDIT- I used Fredo Bezier Spline set for my example, I find the Trimble one a bit clunky for my liking. @catamountain

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Which bezier curve plugin create the original curve?

The first, sample bezier curve plugin created by @last and now Trimble, is a basic sample plugin to use and learn from. While the developer of BezierSpline learn his lesson and developed his plugin to address many of the shortcomings of the original plugin. (Free to join SketchUcation and download.)

With BezierSpline, one can recreate a polycurve from selected bits and recreate one of the bezier curves his plugin creates by selecting the bits > r-click for context menu for options.

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@Thorleyian Thanks a lot for your demonstration. It clearly shows that crossing it with other lines breaks it, so I know one thing I don’t have to do…
The remaining problem is that, in my example, I just drew it and joined with others, without crossing it whatsoever. Moreover, that didn’t affect it at the beginning, it was just after some time… I’ll try again and I’ll test it further and try to find the extension you use here…

I use Bezier Tool, which fitted my needs. But I never tried BezierSpline and it looks great. I’ll try them both and see if the problem disappears… (will report back in a couple of days)

Thanks a lot…

Here is the spline set:

If you go to and install their toolbar for SU you can install the above from within sketchup itself, much like the extension warehouse. Find that here:
Plugin Store Download | SketchUcation

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