Contemporary methods of interaction in 3D space have
Some of the possible enhancements of the interaction
Scene visualisation is mostly 2D (on the monitor), but displayed objects
are three-dimensional. Usage of projection helmets and glasses
is not common practice because of low resolution and high price. Usage
of lasers or volumetric displays for displaying 3D images is in development
and is not suitable for general usage yet.
Input devices are mostly constructed for using in plane only. Mouse
and tablet can be used for interaction in 3D space, but there is a need
for some additional support from software and abstraction of the user.
Typical is employment of three views to the scene - one top-view, one front-view
and one from the side (3D Studio from Autodesk). Another approach is one
perspective view combined with one additional view defined by the user
(TrueSpace from Caligari). Both this systems employ various constraints
to cursor movement, such as snap-modes or movement in one or two axes only.
These are needed to simplify the interaction with objects in the scene
for the user.
Enhancing existing input devices. For example "SpaceBall", joysticks
with spinning handles, force-feedback devices etc.
Using devices, which were constructed for 3D interaction from start.
Examples are data-gloves and 3D mice.
Motion--capture systems. These are used mostly for animations and
are too expensive for the common use.
1.1 Types of 3D locators
Optical and opto--mechanical systems. Optical systems use markers,
which are placed on the moving object and tracked with cameras. They are
used mostly in motion-capture systems. Opto-mechanical systems employ glass
or plastic fibers, acting as waveguides. When the fiber is deformed, light
evades from it and this can be detected as change in the intensity of the
light on fibre's end. Typical usage is in data-gloves and data-suits.
Mechanical systems. These use complicated system of arms and ankles
with several degrees of freedom. Each ankle has sensor for detecting angular
movement, some systems are equipped with force-feedback. They are accurate
and relatively cheap, but rather unwieldy. They are used mostly in robotics
Locators employing acoustic waves. Usually work with ultrasonic
signal, idea is very simple - they measure Time Of Flight
(TOF) of the emitted signal from transmitter to several receivers. Using
at least three non-collinear receivers enables calculation of the position
in the working volume. This principle was used in the design of the 3D
Magnetic trackers. Magnetic sensors are widely used because they
are cheap, but they have several disadvantages - low accuracy, sensitivity
to interference caused by large metallic objects and small range.
GPS based systems. These are used mostly in robotics and navigation,
have only limited usage in VR, because they don't work inside of buildings,
have low resolution (several meters) and are very expensive.