Why do my traced sketches come in as a bunch of broken lines instead of closed shapes?

When lines are open, it almost always means the tracing engine couldn't detect a full path between two endpoints. It's not ussually a major failure of the tool, but rather a problem with the source image itself. Thin strokes tracing worse than thick ones is a weird artifact, but it often indicates high contrast lines that are too faint or slightly fuzzy at the edge, making the automated detection messy. Try increasing the contrast and sharpening the edges of the original drawing in an image editor before feeding it in. That usually helps the algorithm distinguish the desired line from the background noise. For lines that cross, that's normal behavior for a tracer, and yes, it can absolutely confuse it. It sees an intersection and treats it as two paths meeting, which can lead to those little stray fragments floating around. Don't just delete them, though. It's better to fix the input first. If the crossing points are messy, the tracer creates jagged, unreliable nodes. If you can simplify the original drawing—maybe just using dots to indicate where lines should cross rather than actual thick lines—it gives the tracing engine a cleaner, more logical input.

As for how clean the drawing needs to be, there's no absolute rule, but if you're using a trace function on a general photograph, you need high-fidelity line work. The cleaner the lines, the less the AI has to guess where the path starts and stops. If the drawing is done in pencil, scan it at the highest DPI possible, and then run it through an image editor's 'threshold' filter to turn everything into pure black and white before putting it into the tracing system. This eliminates gray tones and fuzziness. If you are getting too many stray fragments, those are just the tracer's attempt to close every minuscule gap it finds. If they are tiny and unrelated to your main shapes, you can usually delete them in the review step before the import. But if they are fragments of a larger shape that failed to close, then fixing the input source is the only reliable fix. Think of it as guiding the computer, not just letting it guess.

I've run into this when I'm trying to trace complex gear teeth instead of just a simple logo. When the geometry gets really intricate, even if the lines look perfect, the tracing software starts choking on the sheer amount of path data. It's like it gets overwhelmed by the nodes. I found that if I simplify the initial image drastically and run it through a vectorizer multiple times, the resulting sketch is usually much more robust, even if it loses a tiny bit of visual fidelity. You gotta strip it down to the absolute basics before you try to add detail back in later. It's just gotta be manageable for the algorithm.

This thread is helping me figure out my own mess. I took a picture of a stencil on my kitchen table under the ceiling light and the tracer kept missing chunks on one side of the drawing. Turned out the shadow from my hand and the slightly wavy paper were making parts of the line look gray instead of black. I redid the photo outside in flat daylight on a hard flat board and it came out way better. Does it matter what angle you take the picture from, or is straight above the only way that works?

Not sold on the dots-at-crossings idea from earlier. If you swap the actual line crossings for dots, the tracer just sees a gap in each path, so you end up with more open loops, not fewer. I tried something like that on a stencil pattern and it made the mess worse. What actually worked for me was accepting the import won't be perfect, then fixing the worst offenders in the sketch editor itself, dragging endpoints togather til the loop closes. Doing that on a dozen shapes takes maybe ten minutes, way less than fussing over the photo forever. At some point the cleanup in CAD is faster than chasing a perfect source image.

Quick update—reading the comments about the software choking on intricate path data was really helpful. I took the messy input file and ran it thru a simple filter to strip away all the tiny, unnecessary pixel detail. It was a drastic change, but the tracer handled the simplified geometry much better, producing fewer fragmented pieces than before!