I exported a circle as DXF, and imported the DXF into CorelDRAW. Got the polygon.
The perfect circle you display is actually segmented, but its display has been visually arranged by algorithms that work for 2d vector drawing. So, it’s an illusion. In 3d, it is a little more complicated.
On the other hand, in SketchUp, there is no vertices lists internally. Circles and arcs are not described by vertices, but by a list of edges. Vertices are stored in edges which are the basic entities instead of vertices. This was an originality of the SketchUp patent (now expired) compared to other 3D software that used lists of vertices . This has qualities (flexibility, simplicity to manage) and disadvantages like those you describe.
Sound advice. I’m always looking at instructional videos. I’ve only been using SketchUp since 2019, so I consider myself a student. But as you point out, the day you stop learning is a very bad day. I lend a hand, every now and then, to a very experienced builder. He’s in his 60s and has decided to stop learning. He’s reached his limit. He knows an awful lot, but not everything.
I am 71 and still learning.
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Yes, I know the work around. Just asking a question about the 2D export.
The 2D DWG output is the same as the PDF or EPS output. It renders the image exactly as seen on screen as a vector image then wraps them inside the autodesk DWG container.
The 3D output retains more metadata about the entities and scenes - such as whether a circle is a circle. And DWG readers can render that as they wish.
I’m not sure what the rationale behind the 2 modes is - personally I think it is responsible for many many bad practices and problems for users when it comes to trying to grapple with what an Autodesk DWG or Adobe PDF file IS.
I’m replying to this post only because it iterates a misconception prevalent in this discussion.
The MS Word circle, the CorelDRAW! circle, the AutoCAD circle, and the SketchUp circle as displayed on your computer monitor is neither a vector or a nurbs or bezier. It is a raster representation of the math that defines the circle. The same thing occurs in your printer, and other places where circles are needed. (This is also true of all other curves in computer modeling, by whichever program produces them.) Mr. Clark may indeed be correct in one very narrow aspect of the problem about which he complains but which is not a problem at all: The image of the circle on the computer monitor is a series of pixels arranged in approximately the region defined by the circle formula, i.e. a series of points equidistant from another point on a plane. AutoCAD’s ViewRes setting is almost identical to SketchUp’s “number of segments” setting in that they both make the circle LOOK smoothly round.
It’s interesting to note that when using a model created by SketchUp, AutoCAD, FormZ or 3DS Max (all of which I’ve used) to MAKE A THING, as opposed to just MAKING A PICTURE OF THAT THING, the computer converts all that amazing math inside the software to a series of planes. Which are converted back into math by the 3D Printer slicer, the CNC machine, the milling machine and then produce apparently smooth surfaces by moving the print head, laser, cutting tool ins super tiny, but still DIGITAL STEPS
For years, I produced drawings of three dimensional structures (buildings, machines, furniture) using a sharp pencil, the best compass I could buy and a straight edge. Had to fudge lots and lots of stuff, but by some miracle (to which I credit the craftsmen who did the real work) those objects were produced, occupied, looked at, sat in, and enjoyed. Truly, people, the small errors in finding tangents (the really only difficulty I find with SketchUp’s circle algorithm), never manifested in the real world objects I designed.
Not perfect.
But good enough.
And probably the best advice I’ve received in this place is "it works. Maybe not with complete elegance, or precision (although that’s pretty amazing for what the softwre costs), but there is always a work around. Learn what that is and move forward.
And to everyone else here, I am amazed at the patience so many of you have exhibited with Mr. Clark’s refusal to accept things as they are. Kudos to the SketchUp team, to the learned ones, and to the Sages.
Now get back to work. 
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Thanks Adam
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If there ever was a chance for a clever plug-in developer to make a plug in for the circles and curves it’s now. It must be possible given the incredible stuff there already.
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Please re-read the thread. Especially the parts from the SketchUp team about the underlying way the program works.
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I agree with you.
You are absolutely uninformed.
But you still are one of the best Motorsport drivers of all times.
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Can you summarize your need regarding circles and arcs?
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I’m thinkin’ … the very best ever!
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I’m not necessarily opposed to using AI to help organize a response but leaving this in seemed like serving up the AI without really looking at and thinking about the response:
Would you like to explore an example application or a related concept?
Using the new Summarize feature may have helped with this?
But if you’re going to use AI @jamesclark why not use it to learn about 2D vs 3D software, surface modelers vs solid modelers, etc.?
I think your feature request is a good idea and not unreasonable to discuss. But the general AI response on circles? SketchUp uses polygons!
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What a |-:L
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That is wrong. SketchUp uses arcs and circles. But when pulling them into surfaces, it uses polygon approximations as it is a polygon modeller. Arcs and circles retain their properties when exported to an application that supports arcs and circles, like CAD. Well, I don’t think this thread is going anywhere.
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That response was generated by Copilot. I summarizes what I’ve always understood about CAD.
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Hi Anssi, I’m not sure what you mean. I can’t find “circle” in the SketchUp ruby API (not including Layout). As far as I know, ruby can be used to make true circles with add on libraries but I’m not sure about that being the case with the version used in Sketchup.
The API does have this entry for curve:
The Curve class is used by SketchUp to unite a series of Edge objects into one conceptual entity. Since SketchUp is a surface modeler, all circles, arcs, and arbitrary curves are really just edges that are bound together in sequence.
Class: Sketchup::Curve — SketchUp Ruby API Documentation
Here is an example from SketchUp that creates a sphere. It uses a polygon with 48 segments:
But even if SketchUp (ruby) can create circles, I’m not sure that OpenGL can draw circles? Can OpenGL be used to draw true circles?
If SketchUp can do this and I’m missing it please let me know what I’m missing.
As far as circles being created for exports, don’t the exporters draw the circles that other software can reproduce?
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I thought Thom gave a rather informed response earlier regarding how AutoCAD works. Not much different than SketchUp, except AutoCAD breaks things down to a far greater degree of detail. AutoCAD’s “circles” are not really different than SketchUp. In fact there are nothing but straight lines in NURBS. I personally regard SketchUp as a first rate CAD package. You don’t … why?
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