Game Development Reference
In-Depth Information
Figure 7.9 3D SpaceBall mouse. (Illustration: Immersion S.A., with permission)
Nevertheless, using software, we can command only object translations or rotations
(Figure 7.9).
The LogiCad 3D “Space mouse'' operates using a movement-measuring optoelec-
tronic system. The maximum force applicable is 4.5N and the maximum torque is
0.1Nm. The resolution is 600 increments.
Please note that a manufacturer offers a 3D mouse using the same principle as the
ultrasound location sensors. It consists of a fixed base with three emitters in a triangle
and a mobile handle with three receptors in the same position and of the same size
(a few centimetres). The operator can move his hand in the measurement space, even
if the latter is limited to an area close to the base (use on a desktop). In this case,
the boundary between the location sensor and 3D mouse is narrow. All of the 3D
mice evidently have several command buttons. For the 3D mouse, the operator cannot
completely ignore the handling of this type of interface during its use, which leads to a
lack of transparency which is detrimental to any natural immersion in a virtual world.
7.3.2 3D Mouse with force feedback
Under the INRIA ALCOVE project, the LIFL and L2EP laboratories, of the Université
des Sciences et Technologies of Lille, have developed an interface called “DigiHaptic'',
based on a decoupling of degrees of freedom (Casiez et al., 2003a).
Digi-Haptic has three force feedback joysticks that can be handled with fingertips
using the thumb, index finger and ring finger (Figure 7.10). The joysticks can be
used separately or simultaneously in twos or threes, irrespective of the mode of use:
isotonic, isometric or elastic. Each joystick includes a direct current motor with cable
drive. Their angular position is indicated by a potentiometer (Figure 7.11).
The characteristics of each degree of freedom are as follows:
work area: angular displacement of 120 degrees, i.e. 4 cm of distance covered by
a finger;
maximum force: 2N continuous.
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