A graphics toolkit based on differential constraints

Abstract

This paper describes Bramble, a toolkit for constructing graphical editing applications. The primary focus of Bramble is improve support for graphical manipulation by employing differential constraint techniques. A constraint engine capable of managing non-linear equations maps interactive controls and constraints to object parameters. This allows objects to provide mathematical outputs that are easily composed, rather than exposing their internal structure or requiring special purpose interaction techniques. The model of interaction used with the differential approach has a continuous notion of time, which provides the continuous motion required for graphical manipulation, Bramble provides a LISP-like extension language and support for other application features such as windows and buttons, The paper concludes with examples of interaction techniques defined in Bramble and applications built with Bramble.