Usability Guidelines for 3D user interfaces

Good 3D user interfaces are difficult to design and build. They may be also difficult to evaluate properly. Unless your implementation is very good you risk the possibility of measuring results that are due to particular issues of the implementation rather then technique limitations. Since building them takes a long time and effort, it would be good if we could predict how a specific technique would fare before investing too much time in the implementation.

In usability engineering we can use different levels of prototype fidelity to communicate ideas and evaluate concepts before a full-fledge prototype is built. They can range from simple textual descriptions and sketches to fake interfaces and wizard of oz approaches. If we are evaluating interaction techniques and in particular 3D user interfaces the lack of fidelity in the prototypes make it difficult to trust any evaluation result. However we must agree that at least *some* characteristics exists and can be evaluated without experiencing the actual real interface.

During this semester I have researched the literature trying to find methods that could be used to evaluate early stage low fidelity prototypes of 3D user interfaces. Most of the methods of evaluation of 3DUI involve mixed methods and at least a empirical evaluation (either formal or informal). Usability guidelines are useful but most were created as aid in the exploration of the design space, rather than in evaluation.

Despite that, I could find three good sources that discuss important things in 3DUI that could be melded into a set of guidelines for analytical evaluation of  low fidelity 3D interfaces prototypes:

• Daniel Wigdor and Dennis Wixon. Brave NUI World: Designing Natural User Interfaces for Touch and Gesture (1st ed.), 2011
  

• Kalawsky, R S. VRUSE - a computerised diagnostic tool: for usability evaluation of virtual/synthetic environment systems. Applied ergonomics, 1990
  

• Doug A. Bowman, Ernst Kruijff, Joseph J. LaViola, and Ivan Poupyrev. 2004. 3D User Interfaces: Theory and Practice.

Based on that I've come up with 4 categories that I consider essential for such a guideline:

1-Metaphor use: The system should be based on a known metaphor so that the user can leverage his understanding of the real world to operate.

2-Gesture design: The gestures should be easy to perform and support the user by using constraints and limited degrees of freedom.

3-Gesture feedback: The interface should respond to every gesture and the interface should provide means to guide the execution and understand the results of the actions .

4-Visual design: The visual layout should support the metaphor and fulfill the user’s expectation in terms of meaning and consistency.