Default UI Menu: Modify/Modify 3D Objects/Surface Mesh/Split Face by Isoline
Ribbon UI Menu:
This tool splits all normal faces along a common isoline (a plane cutting through the object). To Split Faces:
Select the tool.
Hover over an edge of a face, the isoline will be drawn perpendicular to the edge.
- Click to split the faces along the isoline.
Note: Isolines do not cross merged faces.