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

https://future-wiki.win/index.php/Copper_Line_Set_Benefits_for_Residential_Cooling_Systems_54416

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.