Integrating constraints and direct manipulation

In this paper, we present techniques for integrating constraint and direct manipulation approaches to geometric modeling. Direct manipulation positioning techniques are augmented to provide the option of making the relationships they establish persistent. Differential constraint techniques are used to maintain these relationships during subsequent editing. Issues in displaying and editing constraints are also addressed. By integrating constraints with direct manipulation, it is possible to build systems that provide the power of explicitrepresentation of geometric relationships and the properties which make direct manipulation so attractive.