Back in the early to mid '90s I cut my 3D teeth on Ray Dream Designer's Freeform modeler. It's nearly identical to this modeler. In Ray Dream you had a three-sided box. You'd draw shapes on the two walls and floor and the program would create the 3D shape. It was pretty powerful for being such an inexpensive app.
Ray Dream went on to become Carrara, and I think it still uses the same type of modeler.

Steve S