A method and system for making computer-aided drawings of an object directly in 3D. The object or its parts are bounded by m-dimensional enclosing subspaces whose boundaries are shrunk to intersect the topographical features of the enclosed object or its parts. The resulting boundary-boundary intersections define a set of key bounding dots which can be connected with mathematical entities such as lines, surfaces or solids to complete the drawing of the object or its parts. The entire drawing process is conducted directly in 3D on the display device with the user in control to view, freely rotate, move, pan, zoom, create, change or review the object anytime, akin to holding the object in hands in front, and looking over it while creating it. Drawings created by the invention can be grouped to represent assembled components, sub-assemblies, or entire systems. All or part of a drawing, if applicable, can also be grouped for structural modeling and analysis.