ABSTRACT
Mathematically, a plane is defined in terms of three non-collinear points, assuming that the plane so defined is flat and has no boundaries. In CAD practice, planes as 3-D objects always have some thickness, however minimal this might be, and are also bounded objects. To construct such a plane, therefore, involves firstly generating a 2-D form such as a rectangle or polygon, and then extruding this form by some amount. The 2-D form will give the plane its shape, and the extrusion its thickness.
