The ability of an engineer to visualize and reason about geometric aspects
of physical objects and processes is crucial to the success of engineering
activities. The article describes the development of geometric operations f
or a visual reasoning instructional software system using so-called missing
view problem. The missing view problem requires construction of a valid so
lid given two orthographic projections. Sweeping operations, which are the
reverse procedure of orthographic projection, are used to solve missing vie
w problems by forming the boundary faces of a solid from the loops of ortho
graphic views. Specifically, this geometric operation which forms a primary
user interface of the system is described in detail in the article. (C) 19
99 Elsevier Science Ltd. All rights reserved.