I’ve noticed a behavior in the trim tool I’d like to confirm is working as-designed or if this is a bug. The trim tool doesn’t always seem to result in intersecting end-points. This isn’t a problem on straight lines at any angle but seems to be consistent with curved lines.
The setup is here:
“Problem” view:
I’ve noticed this can create a problem with unclosed or hard to close paths.
Is this expected behavior?
Thank you for reporting this. Please share, which OS and version of LightBurn you are using. 
This happened to me just a little while ago as well. I was trimming that dog paw and rectangle and the nodes wouldn’t join automatically, I had to drag one on to the other.
I’m using LB 1.0.04 and Windows 7
What zoom level was that circle intersection? What is the length of that segment?
I am able to duplicate the behavior you are seeing as well, and yes, this can be expected. LightBurn uses Bézier splines to represent circles, and the representation isn’t “perfect”, but it’s darn close. The approximation is very close, but not exact, and well within the accuracy requirements of a CO2 laser.
LightBurn version: 1.0.05
OS: Windows 11
The zoom level was literally as far in as I can go. It’s very tight.
Length doesn’t reach .00mm according to the pen tool. Measurement tool doesn’t work because the segment doesn’t end where the lines cross.
It’s not a problem for me in terms of approximate burning. But it’s a bother when it appears to break a design. If there’s any approximation going on I think it would be preferable to force snapping of the ends even if it nudges a line specifically as to not break design expectations rather than the current approximation where it can leave gaps or overshoot the intersection.
Would the team be open to a feature request on this?
We are always interested in hearing folks ideas, please.
Thanks @Rick. I’ve created a feature request for this:
Trim tool improvements to require intersecting end points · LightBurn (fider.io)
If you are wanting to trim that section, have the result be a closed shape, the Boolean Modifiers are the fastest and best choice.
Ironically I primarily use boolean modifiers but wanted to see how the trim utility could be used so that I’d have that available to me. My assumption had been that results from trim and boolean should be the same.
Adobe Illustrator uses an interesting but similar paradigm with their shape builder which is probably their most innovative tool. The results can all be achieved using boolean operations but the shape builder works from a user perspective similarly to the trim tool in that you can join adjacent portions of enclosed intersecting lines by “trimming” out lines.
Intuition suggests that trim should behave similarly from a user perspective. One pattern of intersection behavior shared between boolean operations and trim operations rather than two distinct patterns. I understand from an implementation perspective these can be different.
It’s not really a perspective - you If you remove a single line, like this:
The circle on the left is still closed, but the one on the right is now just an arc. The trim tool intentionally leaves it this way. It’s a tool used for shape editing, meant to be similar to scissors in other applications.
If what you truly wanted as a result was a closed shape with a cutout, then the Boolean difference tool would be the correct tool for that task.
The base issue for me isn’t whether or not the shape is closed, it’s that subsequent operations that depend on intersections cannot be performed reliably. From a pure utility perspective I rather like the idea of being able to trim away lines leaving an unclosed path. That’s useful.
I guess where this threw me off is that other scissor tools I’m familiar with do not trim to an intersection. They’re basically snipping out sections of a segment where you specify. CAD tools I’m familiar with that allow trimming to an intersection typically preserve the joint between end point and line.
Anyway, as long as I know this is what to expect I can use the tools accordingly.
Thanks for the insight.
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