How to make perfect smooth arc or circle?

livemixer

You can change the number of segments in arcs in the same ways you do for circles; for instance by typing "20s" (or just 20) in the VCB & pressing return before drawing it. Or you can select an already drawn arc that has not been modified & change its number of segments in the "Segments:" field of the Entity Info window & pressing return (or selecting something else) to finish the change.

In SketchUp, there is no such thing as a perfectly smooth circle or arc. They are always constructed from straight line segments.

banan666

Ok, it works with arc too. But is there any program, plugin whitch I could use with drawings made in sketchup to convert ready *.dxf files to make simple lines, or as little as possible? Because in the Ucancam program it read my drawing like made of a thousand lines and the cnc machine have to work much, much longer and the shape its not perfect like it shuld be. I need to convert somehow lines or arcs made in sketchup to simple ones.. but how to do it?

livemixer

By "simple lines" I assume you mean smoothly curving, unsegmented ones, something like you would get by drawing a circle on paper with a compass, right? If so, I don't know of any way to convert SU files to ones that define circles & arcs that way; IOW strictly in terms of a center point & radius. Sorry.

bpl-rfe

Hello banan666.

Just my 2 cents ...

In my personal opinion you have four possibilities:

1.) try to live with situation given.

2.) export to dxf and then correct (that means delete and draw new ones) all arcs and
circles in your drawing/file
For that you have to use a 2D CAD-Program like for example LIBRECAD (http://librecad.org/cms/home.html) .

3.) since DOUBLECAD (http://doublecad.com/) works with Sketchup maybe you could give it a try
and export from Sketchup to DOUBLECAD and then to dxf.
Maybe that will give you perfect arcs ?
Since DoubleCAD XT is free for personal use you could give it a try.

4.) If you want to keep 3D abilities and want to have "real" arcs and circles,
maybe you should think about investing in a NURBS Modeller like
VIACAD (http://www.punchcad.com/p-9-viacad-2d3d-v8.aspx) or TurboCAD or something similar.

Roland

pegaze

to do that, i use solidworks,

in this way, the CAD machine recognize the arc or circle as a simple line.

i would be interrested by finding a plugin able to do that in sketchup.

TIG

A 2d dxf exported from SketchUp always has segmented arcs/circles [that's the way SketchUp makes them in the SKP Model]
However, a 3d dxf export should retain any Arcs as CAD-arcs and any Circles as CAD-circles - i.e. with NO segmentation at all...
If you have extruded a curve or exploded it, and by that it's lost it 'arc-ness' it will be individual segments.
The best you can do there is to make the original arc/circle with lots of segments [perhaps 360 v. 24 ?], before doing any changes to it in the Model...
You can set an arc/circles segmentation when it's made with the native tools [just type in a segment count before picking a point, or after it's made a number followed by an s - e.g. 360s], or later on [provided that its not been incorporated into a 3d form etc] in 'Entity Info' just enter a new number.

djh

Thank you, livemixer.

Garry K

I'm not impressed with Sketchup's DXF import and export and that is why I wrote my own import (my ruby code has very simple requirements) and I wrote my own DXF outside of Sketchup in C++.

Sketchup's DXF import

Creates circles with something like 92 segments. This is way too many segments for tiny circles and way too few for very large circles. I've adjusted the number of segments based on radius.
Puts geometry on layers without groups.
Very slow import

My CabMaker plugin exports information in a csv file about each part. The C++ program uses rules and then creates DXF file with real circles complete with radius and extrusion (pushpull).

Cabinet side panels can have hundreds of holes for shelf supports, dowels, minifix or rafix connectors and they have to be absolutely accurate. I saw no real way of having Sketchup do this kind of work.

bjnobre

Will sketchup support real arcs and circles in near future? There is a roadmap for it?

Dave R

@bjnobre said:

Will sketchup support real arcs and circles in near future? There is a roadmap for it?

Who knows? Anyone who might know would be prohibited by law from telling since Trimble is a publicly traded company.

Box

It could be argued that they are already supported because they can be exported as true arcs and circles.