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In many 3D user interface designs, users are
presented with an array of items (pages, objects, and controls) that float, un-tethered
in the 3D space. Because the typical user is viewing these environments through
a non-stereoscopic display it becomes quite difficult for her to determine
where in depth each object lies -- the relationships between objects in the 3D
environment is perceived as ambiguous. In the real-world there are many cues
that make this easier such as shadows, parallax, atmospheric shading, binocular
disparity, and physical connection. The 3D user interface designer's job is to
gather take advantage of a set of cues in an attempt to overcome the
shortcomings of the virtual world. Within the constraints of the desktop
environment, we have added the following cues:
Interactive audio for the Task Gallery is functional, not decorative (every
attempt has been made to code useful information onto the audio events). Buttons
are spatialized according to left to right position and each button’s timbre
is subtly unique. There are rollover sounds that assist the user in locating
specific tools.
Objects are dragged on the pallet, objects are moved on the stage, and tasks
are moved in the room -- each with its own distinct dragging sound that is
spatially and gesturally dynamic. Volume, timbre and stereo positioning are
controlled in a way that simulates the sound of the type of object that is being
moved (as an object is moved farther away from the user's viewpoint its sound becomes more
distant). When the user moves a task there is a continuous sound proportional to the user’s gesture
and each surface is distinguishable; floor from ceiling, left wall from right.
When the user moves a task from a wall to the floor an additional sound confirms the discontinuity caused by that interaction. This increases the
user’s sense of efficacy and is specific audio confirmation of that exact
action. Run-time
synthesis of pre-rendered basis sounds binds user interaction to audio. Simply playing back audio clips
synchronized to user interaction does not have enough information to warrant the
user’s attention. We have tried to make each audio event convey useful
information. User interaction is coupled to
the audio, thus reducing the need
for users to visually focus on the detail of every gesture
Validation
The validation of these cues comes in two
forms:
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Feedback from our User
Studies has been quite positive and users have generally been able to
understand and navigate our 3D environment
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3D first and third person perspective games
are starting to take advantage of many of these cues. These cues let users
focus on the "fun" aspects of the game without having to worry
about navigation or disambiguating 3D object relationships.
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