Cross-section of a cuboid through three points

Mathematics3D GeometryAges 16–17

The cuboid ABCD.A'B'C'D' can be rotated by mouse or touch. Three points M on AB, N on AD, and P on CC' can be dragged along their edges; the simulation constructs the cross-section of the box cut by plane (MNP), shades the cross-section polygon, and highlights the pairs of parallel intersection lines on opposite faces.