Section: Scientific Foundations
3D interaction
- Interaction:
the location of two people in the same place, if they are conscious of this, induces an interaction between them. An interaction consists in the opening of a loop of data flow transmission channels between them making sense on each of them and modifying their own cognitive state.
3D interaction is an important factor to improve the feeling of immersion and presence in virtual reality. However, the introduction of a third dimension when interacting with a virtual environment makes inappropriate most of the classical techniques used successfully in the field of 2D interaction with desktop computers up to now. Thus, it becomes necessary to design and evaluate new paradigms specifically oriented towards interaction within 3D virtual environments.
Two components are classically isolated when considering 3D user interfaces and 3D interaction:
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the interaction device, which sends the intentions of the user to the virtual environment (input device) and/or feeds back some information to him/her (output device);
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the interaction technique, which corresponds to the “interpretation” of the information received or sent to the user by the system, i.e. the scenario of use of the interaction device when considering a specific task to be achieved in the virtual environment.
The design of 3D interaction techniques is conceived as an iterative process of design-evaluation-redesign which ends when the technique reaches its criteria of use. Another objective of the evaluation of the 3D interaction technique is to determine the model of performance, i.e. the prediction of the performance of the user given a certain task and a certain 3D interaction technique. The most famous example is probably the Fitt's law (Equation 4 ) which predicts the time (T) spent to reach a target with a given width (W) and located at a given distance (D). In this equation, the constant a and b are determined empirically according to the pointing task and the interaction device used.
The methods used to evaluate the 3D interfaces correspond to the standards defined in the field of 2D Human-Computer Interaction. We can distinguish the comparative evaluation which compares the performances of several techniques on the same task. Then the heuristic evaluation relies on the knowledge of a group of experts, who assess the efficiency of the technique, taking into account the standards and the design rules of their area. Other techniques like questionnaire and interviews are often used as a complement of the previous methods. Several questionnaires have been set up for instance to address the subjective feeling of presence in virtual environments.
