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Problems with exported arcs and circles in SVG/DXFs (by Zack)

This is probably caused by the enormously crappy laser cutter software that our FullSpectrum Laser uses, but the parts I've designed in SolveSpace have issues with arcs and circles.

So the process I've got is SS 3d part -> select face -> export 2d section (to SVG or DXF).

When I load the export into either Inkscape or Draftsight, I found that circles are exported as four connected arc segments, but the first and last segments don't connect to each other, and arcs/chamfers are only connected at one point. My understanding is that circles should export as smooth continuous curves in SVG, but maybe I've misinterpreted how the exports should behave.

Wed Mar 5 2014, 01:45:56, download attachment
(no subject) (by Jonathan Westhues)
What do you mean by "don't connect to each other"? The SVG output won't have much human-editor-friendly structure, but the loops should be closed to within a very small numerical tolerance (~1 nm). What problem are you having with the laser cutter software?

Independently of the root cause of your problem, if it affects arcs but not lines then you might be able to make it go away by checking "export curves as piecewise linear" in the config screen.
Thu Mar 6 2014, 04:34:33
(no subject) (by Zack)
In Inkscape, if you use the node selector tool, you'll see that export circles are composed of four connected arcs, of which the first and last arcs aren't connected to each other. The end point of the last arc and the start point of the first arc are co-terminal but aren't connected. Same for single arcs, the start point for the arc isn't connected (stay on a chamfer, to the corresponding line/etc.). At least in Inkscape this is easily fixed, if you select the node tool, and select all nodes in the SVG, you can use the merge node tool and it'll automatically merge the nodes correctly for the entire SVG. Another important option in Inkscape when working with the export SVGs is to select all nodes and use the break apart option. This will allow you to modify individual paths in the SVG, since the exported SVG is exported as a single path. In my case, I needed to do this to change the line color for certain features so I could tell the laser cutter to use different cutting parameters for them.

The problem with the laser cutter driver is that it interpreted the circles and arcs as open surfaces (? not sure what the correct term is), so when using the cutter vector mode, it wouldn't recognize them. As I said above, I figured out how to fix it in Inkscape by merging nodes, but it turns out that the cutter driver is buggy anyhow, so printing from Inkscape to an XPS file allowed the cutter to read the file just fine.

So TL;DR: The problem was really with the cutter driver, but I'm still curious if the first and last arcs in an exported circle should be connected.
Thu Mar 6 2014, 14:04:22
(no subject) (by Jonathan Westhues)
Upon inspection, I'm not generating the close path ("z") commands in my SVG output. I should probably fix that; it doesn't matter in most cases, but I'd guess that's what does in yours.
Mon Mar 10 2014, 02:08:04
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