Zoom-in on the evolution of segmentation results as a function of the classification threshold showing the filamentary structures estimated by UNet++ 10^–3 in 160–171° (six top images) and 349–356° (six bottom images) regions of the Galactic plane. The original H₂ column density image (top left in each group), the ground-truth input filament mask, and the corresponding segmented image at different thresholds (0.8, 0.5, 0.2, and the optimal threshold) are shown from top left to bottom right. The regions are 2° × 2° wide.