Sketch Input of Engineering Solid Models

Abstract

In this tutorial, we describe the state of the art of sketch input of engineering solid models. The tutorial is in four parts. In the first part, we show how sketching has historically been an important aspect of engineering culture,and remains a useful tool in the early design phase as it has been demonstrated that sketching enhances creativity.We discuss and classify various current approaches to computer interpretation of sketches.We introduce the problem of deducing design intent, which we understand as a mix of geometry, psychology and engineering, and note how no existing approach to interpretation of sketches has considered the explicit capture of design intent from the input sketch. In the second and third parts, we present our selection of the most important algorithms currently used for interpreting wireframe drawings (part two) and natural line drawings (part three) of engineering objects. In part two, the algorithms we look at are: for finding faces in wireframes; for inflating wireframes to 3D; and for processing rounds and fillets. In part three, we look at: line labelling; inflation to 2.5D; and deducing hidden topology. In part four, we discuss some of the most interesting open problems: making virtual paper and pencil more usable than actual paper and pencil; interpreting annotated engineering sketches; and creating assemblies from sketches.