Converting unfilled, unclosed paths from Cut to Engrave fills them

In this image of my render, the top and bottom layers are unclosed, unfilled lines/paths (like circuit traces). I converted one of these path sets to ProofGrade engrave to see how it looks, and it has changed it to the equivalent filled, closed path.

When I printed it, it did engrave the inside of path (so it’s not just a UI issue).

Curiously, it didn’t fill it where even numbers of these shapes overlapped (there might be some fun to be had there)

Expected: unfilled unclosed paths should not be filled when converted to engrave - the engrave should just rasterise the path itself.


I guess the obvious workaround is: don’t do that. Or, convert to outlines first.

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You have experienced a basic feature of how Glowforge treats vectors. There have been some lively discussions about how the GFUI handles these cases:

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Thanks @marmak3261. I understand what’s going on now, and I have updated my expectations to align with reality again.

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A few folks with laser experience had to unlearn some things about this. I was starting from scratch so I was able to learn the basics. Even after a year of forum activity and lots of file dissection, I still had a few cases where I didn’t quite get if figured out. Your example is superb though and something that folks can learn from. Thanks for posting.

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Neat! So, the overlapping fills that resulted in alternating fills of burn are demonstrative of the even/odd fill rule oft used in graphics algorithms, it seems! Or, in this case, the GFUI is filling based on the # of closed paths that are stacked. Which is a bit weird, but reasonable.

Tangentially related:

Potentially more directly related. May be fallout from the way the SVG rendering engine is implemented. Interesting.

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Also note that at this time Glowforge only understands fill-rule:nonzero, not fill-rule:evenodd

Well that’s kind of odd, because the result I got looks very much like the effect of evenodd.

I have replaced the result in my post with a better version so it can be seen more clearly.

This doesn’t appear to be a continuous path, though, but overlapping paths?

I don’t know how the SVG fill rules apply across multiple paths.

I’m so sorry for the late reply. Thanks everyone for the great help! @alexbbrown, I’ve passed your report on to the team.

Were you able to get the print you wanted after following the suggestions in this thread?

It’s been a little while since I’ve seen any replies on this thread so I’m going to close it. If you still need help with this please either start a new thread or email support@glowforge.com.