In 3D modeling, a line set defines which edges are rendered as strokes in a non-photorealistic style

https://web-wiki.win/index.php/Line_Set_Protection_Strategies_for_Coastal_Environments

In 3D modeling, a line set defines which edges are rendered as strokes in a non-photorealistic style, controlling visibility, crease emphasis, silhouette extraction, and intersection highlights for stylized visuals.