(for extra context: the points correspond to the orthogonal projection of the vertices of a floating cuboid, changing the angle of the plane changes the "shadow" of the cuboid on the plane. i want that shadow to be filled in.)
The orthogonal projection of a cuboid is convex, but some of the projected vertices of the cuboid will not in general be on the convex boundary of the projected region, so we need to exclude those. This is easily done with convhull
k=convhull(x,y);
patch(x(k),y(k))
