Line Interval controls scan spacing
For Fill and Image operations, LightBurn moves the laser across the design in scan lines. Line Interval is the distance between those lines. DPI/LPI expresses the same idea as line density, so the two values are mathematically linked.
Smaller interval means more lines
Reducing Line Interval packs more scan lines into the same physical area. That increases processing time and energy overlap. It can improve coverage up to a point, but after the laser's effective spot size is already covering the surface, adding even more lines may only make the engraving darker, muddier and slower.
Larger interval means fewer lines
Increasing the interval reduces overlap and shortens the job. Go too far and visible gaps can appear between lines, curved edges may look stepped, and more energy per line may be required to achieve the same darkness or depth.
The goal is not maximum DPI
The practical target is a spacing appropriate for the real laser spot, material and focus. LightBurn's official Interval Test is designed to compare several intervals under controlled Speed and Power settings.