This tool plots curves in three dimensions by creating vertices and edges in the Working-Volume view windows.
The vertices are created at the position of the 3D cursor and the edge joins the new vertex to the last vertex created.
Move the 3D cursor near the place where you want to start the curve. The curve can be started by attaching it to a selected vertex. Place the 3D cursor near a selected vertex. Keep the left mouse button held down. Click the right button to attach the plot to a vertex, or to create a new vertex at that location if there are no other vertices nearby. Click and drag the rubber band edge with the 3D cursor to where you want the next vertex (this can be another edge). Keep the left button down and click the right button. A new vertex will be created and an edge will attach it to the last vertex. If you click on a selected vertex, the edge will join it to the last vertex. If a triangle is formed with any other edges, a face will be added as well. Use the CTRL key modifier to disable the automatic attachment to any existing vertex.
While plotting a 3D curve, you can move between the three Working-Volume views to place each vertex in three dimensions.