Hi all, have been using Sketchup for the past 8 years. Have always been curious if there’s a plugin that supports like true curves, not segmented curves. When I import from Rhino I always get annoyed when my curves are turned into low number segments and I have to redraw this.
I also CNC and am annoyed when my curves from SKP are just a bunch of segments.
SketchUp represents all curves as segments. Although circle and arc metadata may be present, the curve is still segmented.
I figured. I was just curious if there was a plugin or way around it?
Great question. I experience the same thing with my 3D prints. I try to increase the fidelity of my models by increasing segments whenever I am modeling or generating lofts in SU. Still, I think the segmentation is inherent with how the program operates and part of the reason it makes it so easy for beginners to grasp the concept of push/pull, extrude, intersect. Most people struggle with the idea of manipulating true curvilinear NURB based geometry.
Most 3D printers use a slicer application that converts a STL version of the model into instructions for the printer. STL is a triangulated mesh file format so whatever modelling method your 3D application uses your model will get segmented and facetted.
Someone posted a method to calculate your ideal arc segment count depending on the size of the model and the resolution of the 3D printer.
For 2D toolpaths (CNC router,plasma,laser,water jet…) SketchUp can output true arcs in the .dwg and.dxf formats. Although as a surface modeler SketchUp represents all geometry as lines or collections of lines, for arcs and circles it does store the underlying radius info in the metadata and that can be accessed to export mathematically correct arcs.
Basics: Make a 2D shape with either arcs or circles. Place it flat on the XY plane. Set the Camera to Parallel Projection and choose the Top standard view so the camera is looking directly down on the piece. Choose File>Export>3D Model. At the bottom of the export window set the file type to .dwg or .dxf. In the options uncheck all export entity except edges, only export edges. Then push export.
I once did an informal experiment where I 3D printed a cylinder in with different segment numbers to see how it affected print time and fidelity. Granted, this will vary depending on the overall size of the cylinder (this was about the diameter of a soda can), but I found that anything above 36 segments made no real difference to the finished product. There may have been a slight difference between 36 and 48, but 72 was indistinguishable.
I understand. The point is, if the geometry is not as smooth as possible to begin with in your SU model, then obviously you can not recover or produce interpolated geometry with any slicer for 3D printing. Here’s an example of a low segment model that was printed with a high fidelity for printing. No matter how fine you set the slicer/printer, the geometry is absent.
As a comparison, this model was created with a high poly mesh count in SU and hence the smooth refined print:
I have done something very similar. I think it’s extremely important to note this for those looking to 3D print with a fine fidelity to the model. Especially since SU starts all arcs at only 12 segments, and circles at 24 segments.
I typically try to double it, making all arcs 24, and all circular geometry 48.
The only time I will reduce this number is if the model is at very small scale, where the beading of the print is not physically able to distinguish between 6, 12, or 24 segments.