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

https://www.mipiwiki.com/index.php/Line_Set_Insulation_Options_for_Mini_Split_Applications

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.