LightBurn shapes not closed or filling: a diagnostic checklist

Separate the visible symptom from the cause

An unfilled-looking shape may be an open path, a closed path shown with an outline-only style, a hidden or locked layer, or overlapping geometry that creates an unexpected fill. This checklist is version-agnostic and does not claim a LightBurn reproduction.

Use a small before-and-after geometry fixture

These editor-agnostic SVGs isolate the path question: the before file has an open three-segment path, while the after file closes the same rectangle and adds a fill. They demonstrate a geometry difference only; they are not LightBurn screenshots or machining evidence.

• Download the open-path fixture
• Download the closed-fill fixture

Diagnose in five passes

1. Select the exact object Select one suspect shape and isolate it from nearby objects. Confirm which layer and object are active before changing nodes.
2. Inspect endpoints Zoom to the apparent join and inspect whether the first and last nodes meet. A gap means the path is open even when the preview looks almost closed.
3. Check fill and line style Confirm that the object has a visible fill and that the current display mode is not hiding it. A closed path can still look empty when its style is outline-only.
4. Check layer state Verify the active layer is visible, editable and the intended output layer. Hidden, template or locked states can make a valid path appear missing.
5. Test overlaps separately Move nearby duplicates or overlapping paths aside in a copy. Overlap, winding and fill rules can change the visible result without changing whether one path is closed.

Separate duplicate lines from a normal outline

Two visible boundaries are expected when a thick filled stroke has been traced as an outline. Treat a line as a duplicate only after checking whether both paths occupy the same coordinates and whether the source intentionally has two edges.

• Same coordinates and same shape: inspect for a duplicate in a copy before deleting anything.
• Parallel inner and outer boundaries around a thick stroke: this is usually a normal outline; see the outline-versus-centerline guide.
• Crossing or stacked shapes: isolate layers and test fill direction before changing winding or deleting paths.
• A missing fill with one open endpoint: fix closure first; deleting a second-looking line can hide the real cause.

Separate outline from centerline needs

Apply the smallest justified correction

Record the original file first, then change one cause at a time and reopen or reselect the result.

• Close a verified endpoint gap only when the intended join is clear.
• Restore a fill or layer visibility setting when geometry is already correct.
• Separate or delete a confirmed duplicate in a copy; do not remove a legitimate double outline by appearance alone.
• Recheck dimensions, holes and direction after any topology edit.

Keep the evidence boundary explicit

This checklist does not verify a specific LightBurn release, arbitrary file, machine profile or machining result. Parser acceptance and a closed path do not prove that a target editor will fill or cut it as intended.