Solving applied geometric design problems with the use of 3D-CAD

Abstract

With the wide spread use of 3D-CAD in industrial fields, some people say that traditional descriptive geometry is no longer any use. In fact, typical descriptive geometry problems such as finding the true length of a straight line and the intersection lines between two solid objects can be solved much more precisely and much more quickly with the use of 3D-CAD than with hand drawings based upon traditional descriptive geometry. Is the traditional descriptive geometry really no longer any practical use? In order to get some insight into this question, we solve some applied geometric design problems with the use of 3D-CAD, and compare the solution processes with those in traditional descriptive geometry. The results of comparison show the followings: (1) Solution strategies in 3D-CAD are basically similar to those in traditional descriptive geometry. Even in 3D-CAD solutions, the use of graphics representations (i.e., 2-dimensional representations) such as projection from a specified direction, development and sectioning are quite useful. (2) It is, however, not necessary to use traditional rules and compasses to get such graphics representations. Projection function and sectioning function in 3D-CAD are useful in getting graphic representations. (3) Much easier solution strategies are sometimes available in 3D-CAD by applying rich 3D-CAD geometric processing functions such as assembly function. (4) Knowledge on spatial geometry just behind traditional descriptive geometry is, needless to say, still important in 3D-CAD solutions.