Game Development Reference
As we have indicated in chapter 2, in the first category (observation), the subject is
almost always “technically'' passive in the virtual environment, though we know that
human perception is not a passive activity but is often connected to a motor activity,
like the ocular movement of the eyes observing a scene. The subject is “technically''
passive in the sense that he does not use the hardware device to search for the sensory
information in the virtual environment: very few applications use, for example, an eye
tracker to determine the motor activity during eye movements. Tactile observation of
a virtual object is rarely done using a touch-sensitive interface and an interface that
detects the movement of the user's hand.
In the other three categories, the subject is always active in the virtual environment:
he interacts with the environment. To enable the subject to perform these three VBPs of
interaction, it is necessary to use different hardware and software solutions which are
commonly known as “the interaction techniques''. From an academic approach, we
separate the presentation on the basis of these different categories, even if the categories
clash and are incompatible with each other. The reader must understand that they are
cognitively linked for the subject in the “perception, cognition, action'' loop.
Despite its major importance, 3D 1 interaction in virtual reality is currently far from
providing satisfactory solutions. Indeed, the processes of interaction with virtual
worlds are still often very poor. The interface is frequently inspired by the 2D prob-
lem. For example, operations as simple as navigation within virtual 3D scenes, where
handling (movement) of entities in the scene are problems that still initiate a lot of
research. This relative insufficiency of interaction with virtual worlds is all the more
wrongly perceived by the user since the real world, in which we are used to interacting,
is elaborate. Any “machine'', a bit complex (car, cycle, television, telephone, musical
instrument, ... ), has its own mode of interaction, adapted to the task to be completed.
The objective of this chapter is to introduce the domain of 3D interaction in immer-
sive or semi-immersive virtual environments 2 (Coquillart et al., 2000). Unlike some
other chapters, this chapter adopts a more technocentric vision of the interface and
associates itself more particularly with the study of the software layer of the inter-
face. 3D interaction is characterized by three basic components: the motor hardware
interface (input devices), the sensory hardware interface (sensory feedbacks to the user,
output devices) and the interaction techniques that form the software layer. Interaction
technique refers to a method, a scenario of using the hardware interface, facilitating
the user to accomplish an accurate task in the virtual universe. The body of the chap-
ter is devoted to a presentation and an analysis of the main interaction techniques in
virtual environments. The following are considered as the three most representative
generic tasks (Hand, 1997; Bowman & Hodges, 1999): movement and way finding,
1 Interaction with 3D virtual worlds is called 3D interaction as opposed to 2D interaction, which
is an interaction, for which, handled entities are in 2D (2D design, ... ).
2 According to authors, the definition of “immersive'' and “semi-immersive'' notions can vary.
We are using the two terms here to satisfy all definitions. We are including projection-based head-
mounted displays and configurations on big screens with stereo, recording head movements, ...