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3.1 Software Architecture

In this section we are going to discuss the principle components of the software architecture as shown in figure 4, on which the MMVL is based. For one-column wide figures use

Fig. 4. Software Architecture of MMVL

User Interaction. The first module of this model/architecture is the user interaction module. This provides an interface between the user and MMVL enabling the user to navigate and select/manipulate virtual objects. In order to make the interaction more realistic and give more freedom to users, we use wiimote controller as an input device.

Wiimote's Interface. Wiimotes Interface. There are many devices for 3D interaction like kinect, leap, wiimote, ?ystick, joystick etc. In our MMVL we have used wiimote for 3D interaction because it is a cost e?ective device than other 3D interaction devices, it can also provide haptic sensation in the form of vibration. Wiimote is a video game controller that contains on two accelerometers, multiple buttons, a small speaker and a vibrator. For connection with the system it uses Bluetooth technology (see in figure 5). Its workspace is quite large and allows the interaction from a distance of 18 meters. The user in MMVL is represented by a virtual hand which is controlled via wiimote.

Navigation. The virtual hand representing the user can move (navigate) freely in all directions in the MMVL. The position of the wiimote is mapped onto the virtual hand and whenever the user moves the wiimote in the real world environment, the virtual hand follows its motion in the MMVL. The navigation of virtual hand along X-axis is achieved through the rotation of wiimote along its Y-axis as shown in figure 6(c). Similarly the movement of virtual hand along Y-axis is controlled through the rotation of wiimote along its X-axis as shown in figure 6(a). The Z-axis movement of virtual hand is controlled through the up and down buttons of wiimote. Figure 6 shows the 3D coordinates of MMVL.

Selection & manipulation. Selection and manipulation are the important activities in any virtual environment. For the manipulation of an object it needs to

Fig. 5. Wiimote Motion Sensing [13]

Fig. 6. 3D Coordinates of MMVL

be selected first. In MMVL an object becomes selectable when the virtual hand collides with it. After collision if the user presses the button ”A” of the wiimote, the object is selected. After selection the user is able to manipulate it i.e. to change its position or orientation and other attributes. For example he/she can bring the selected chemical or glassware to the table and can place it anywhere by just pressing the wiimote ”A” button again.

Collision Detection. It is a natural matter that one solid object cannot inhabit the space of another solid object. In a simulated virtual environment an object needs realistic responding collision with other objects to show solidity [14]. In MMVL the collision detection module is responsible to check the collision of the virtual hand with all other objects such as chemical and apparatuses. The system performs different actions when the collision occurs. If the virtual hand collides with an object, the audio/visual information related to the object is provided by the system or the object is selected. If a selected object collides with any other object in the environment, the former stops moving further.

Multimodality. The MMVL is a multimodal virtual environment when the virtual hand collides with an object (chemicals, apparatuses etc) its information (such as physical and chemical properties of chemicals and function of glassware etc) is given to the user in the form of multimodal feedback. The multimodal feedback works as cognitive aids for users while performing an experiment.

Simulation of an Experiment. After the successful performance of an experiment the user obtains the simulated reaction and the equation of the resultant products is also displayed on the virtual board in the MMVL.

 
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