This paper presents a design approach to create gestural user interfaces for 3D modelling software tools. Our approach consists of a set of design methods and tools, which: 1) support understanding the user needs; 2) provide means for exploring affordances of 3D modelling systems, tracking technologies, and natural user interfaces; 3) facilitate generation and evaluation of interface ideas; 4) support implementation and validation of gestural UI concepts. The proposed approach has been tested in a case study, in which a hand gesture interface for Autodesk Maya has been build and tested with novice users. The results of the experiment showed that the gestural interface can be as efficient as the conventional mouse and keyboard in terms of tasks performed; and it can result in efficient learning curve while it provides access to all features of Maya.@en