Game Development Reference
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some difficulties: loss of menu that is hidden by objects of the scene and unwanted
blanking of certain zones of the scene;
object-centred positioning is often used in case of widgets;
user-centered positioning, with a sub-division as per the different parts of the body
in relation to which the menu is positioned: body, head and hand. Centre aligning
the menu in relation to the body of the user gives a strong spatial reference that
considerably improves performances using the proprioceptive sense (awareness of
the position of his body) (Mine et al., 1997). Positioning the menu in relation to the
hand also lets the user be partially free from additional dimensions introduced by
3D. Wloka and his colleagues (1995) propose displaying the menu at the level of a
hand-held hardware interface: a 3D mouse (lets the user move closer to or further
away from the menu). Selection is done using the mouse buttons for moving up or
down in the menu. The selection task becomes a 1D task again, but the selection
is not quick;
hardware interface-centered positioning lets the user use the physical reference
point given by the configuration which is very significant in some cases. For exam-
ple, on a workbench, you can place the menu at a fixed position with respect to
the screens that form a strong reference point. On the other hand, this solution
unfortunately does not resolve the blanking problem mentioned in the case of
world-centred positioning.
3D menus or widgets may be more suitable but are still quite rare. Among the most
significant ones, we are mentioning:
the ring menu proposed byWesche and Droske (2000). This menu is hand-oriented
and activated using a stylus provided with localisation sensors. On pressing the
button of the stylus, a ring menu appears and selection is done using a ray from
the stylus. A simple rotational movement of the wrist makes it possible to direct
the ray towards the different commands that are selected by pressing the stylus
button. This menu is quite good to use but the selection is not quick and, more
importantly, the number of commands available is often limited;
more recently, Gerber and Bechmann (2004) picked up on the ring menu concept of
Liang again, but this time only the hemisphere of the ring facing the user was con-
sidered (Figure 12.25). The selection cursor remains fixed, while the Spin Menu,
as named by its designers, revolves according to the rotation of the user's wrist. An
ingenious system of screening considerably reduces the interferences of the user's
movements when he validates the desired input in the menu. It can be considered
that the menu is divided into sections of the same width. When the cursor is situated
Figure 12.25 The “Spin Menu''
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