Computer-Aided Structural Engineering (CASE) Project. Reference Manual: Computer Graphics Program for Generation of Engineering Geometry (SKETCH)

摘要

The primary objective of program SKETCH is to assist the user in creation of precise mathematical models of engineering geometry from roughly drawn pictures. A picture or sketch is constructed in an on-line fashion using interactive graphics techniques. The data base which results consists of three-dimensional (3-D) coordinates, lines, polygonal faces, curves, and surfaces. Curved surfaces, however, are not supported in version 3, modification 1, of SKETCH. A user of SKETCH first interactively creates a schematic representation of the intended geometry. The schematic can be a two-dimensional (2-D) cross section or a 3-D pictorial. Straight lines alone are used in the initial sketch. Polygons or polyhedra defined by the lines are dimensioned by the user and automatically converted to a 3-D mathematical model by SKETCH. Arcs, circles, ellipses, and splines can be added after the 3-D conversion takes place. The original straight lines therefore serve as control information and boundary conditions for the curve forms. SKETCH is designed to allow the definition of any engineering geometry, but is particularly advantageous when creating asymmetric geometry. The results of a sketching session is an output file consisting of coordinates, lines, faces, isolated curve segments, and splines. The files can be created or modified with the system editor, if desired.