Computer aided descriptive geometry

The main aim of this thesis is the creation of a software package for descriptive geometry. Why there is a need for such a descriptive geometry software? In descriptive geometry the ability of space perception is trained by solving spatial problems graphically with the use of a few constructions: Hence the solution of each problem consists of two parts: 1) 3D-part: After analyzing the spatial problem it is cleared how to proceed step by step in space. 2) 2D-part: Due to the basic rules of descriptive geometry for each step of the solving strategy the corresponding 2D-construction has to be carried out graphically. By use of CAD-DG the 2nd part can be replaced again by a 3D-part: Each step is solved using the basic routines offered in the menu. That means that each step is solved analytically but instead of any output of numbers the solution is immediately displayed in the main views on the screen. Therefore the user neither needs to apply formulas of analytic geometry nor has to take care of any coordinates. He still works directly with geometric objects in a graphic representation