Applying constraints to enforce users' intentions in free-hand 2-D sketches

Our system, Easel, is a smart CAD package which attempts to analyse and tidy up sketches as a designer draws them. In this paper, we present an overview of the system, details of its user interface and the curve-fitting approach. The main part of the paper is concerned with automatic methods to infer and enforce geometric relations intended by the user. We also discuss our conclusions as regards performance.