Introduction
Suposse you want to "sketch" your ideas about some project involving 3D shapes. Using a pencil and a piece of paper its the natural choice. Suposse you finish your sketch and you want to visualize it from other point of view, so you have to do another sketch. In fact the more points of view you want, the more sketchs needed. Now suposse you have a system that imitates the pencil and paper method on a computer, such that it can communicate 3D geometry ideas. Here after the first sketch the system quickly convert this rough, two-dimensional image into a crisp, straight-lined 3D virtual model for you to manipulate and view from anywhere!
CSG Sketch Based System
This is just one of the advantages that sketch based systems have. Like Robert C. Zeleznik pointed out in his work "SKETCH" (check the references section), sketch based interfaces are designed to link hand sketches with computer-based modeling programs, and to help designers during the early conceptual design stage.
For the details about a basic Generative Sketch Based 3D system, see the implementation section.