It has been a while (some years ago) since I asked this same question: what is the purpose of having 3D polylines in SketchUp? Why where they ever implemented? Any news “yet” ?
(Other than for tracing some shape and then exploding of course)
I have been giving this some thought recently since I did a mud hut roof example on another thread (tracing an irregular shape).
SketchUp is probably a bit light on organic modelling examples - this particular example gets a lot harder if you try to do it without a poly line.
Ate you guys talking about polylines or just the freehand tool.
3d polylines are those odd things that are difficult to manipulate.
I assumed it was the freehand tool, maybe it’s something else?..but please don’t eat us, it was a simple error!
Draw an edge with the freehand tool but hold shift while doing it.
Then try to use that edge.
I haven’t found any explanation for them in SketchUp help online, apart from this -
A polyline entity doesn’t generate inference snaps, create faces, or affect geometry in any way. You create a polyline entity only if you hold down the Shift key as you draw with the Freehand tool. Polyline entities are thinner than curve entities.
Could they have been created for 2D maps / terrain?
I think it would be a useful tool if you could select a bunch of geometry and convert it to this style of polyline. The fact that you can only select them by a left to right fence around their end vertex means you have linework that is effectively locked and non inferencing. Using Fredo’s convert to Polyline doesn’t have the same basically inert properties that these have.
As the title says, it’s about that mysterious entity that you get when also holding down [Shift] when applying the ‘Freehand’ tool.
Yes, I should have explained the use of [Shift] to get a 3D Polyline, not just a series of edges in a curve.
I didn’t mean you @g.h.hubers I knew what you were talking about.
Hi everybody,
I’m resuscitating this thread as we are investigating some improvements to the Freehand tool and are considering removing the [Shift] Polyline modifier altogether. Is anybody using the 3D Polylines created in their workflow: if so what for?
Thanks for indulging our curiosity!
Mark
When I’m just explaining to someone how to use the Freehand tool…I always tell them to stay away from the Shift key.
Demonstrating what it is, and how amazingly very rarely it is needed. 
Agree!
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What is actually the difference between a “curve” and a “3D Polyline”?
To me the latter looks smoother and I can select it only by enclosing it wholly in a selection window…
I don’t see the modifier listed on the status line when the tool is active so i wouldn’t have known about the feature without reading this thread.
- A curve entity contains multiple line segments but can define and divide a face like a single line. Although you select all the segments in a curve entity at once, the SketchUp inference engine displays point and edge inferences for each segment in the entity.
- A polyline entity doesn’t generate inference snaps, create faces, or affect geometry in any way. You create a polyline entity only if you hold down the Shift key as you draw with the Freehand tool. Polyline entities are thinner than curve entities.
Huh, who knew? 
Thinner in what sense, I wonder?
Then what is it for?
I quoted from official “help.” As far as I can remember from the very beginning it is described this way.
Of course, depending on what style you use, the appearance of “lines” can vary.
Also I quoted from the official help.:
“decorate your model.”
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Now, that is an interesting notion: I can’t say ‘officially’ that we feel this entity is a good way to decorate the model. I’m still hopeful this thread will catch the eye of someone who has figured out a reason for this polyline.
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To me it seems that the polyline doesn’t register as a “profile” while the “curve” does.
I don’t find a way to use the polyline to create faces or anything so, perhaps, it is only good for “decoration”. In that case I don’t see a reason for it.
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