Update functions

The update functions include rotation, zoom and representation change.

Before describing these update functions, it is important to know that the Paraview application has a module called servermanager, which can be used externally with other platforms. servermanager is designed to easily build distributed client-server applications. In this thesis, all the update functions are developed based on this module. In order to manipulate the Paraview visualisation, any interaction between the server and the gateway needs to communicate with this servermanager

module. In servergateway.py script, this module is imported as follows:

To establish a connection between the gateway and the Paraview server, the gateway needs to run the following command in servergateway.py:

connection=servermanager.Connect("localhost")

On the other hand, for the update functions mentioned above, we need to be aware that depending on the bandwidth network connection, there will be time gaps when transmitting visualisations from the Paraview server to the mobile client.

 Zoom function

Users can apply the zoom function to the current visualisation on the mobile client to zoom in or out. The zoom function requires users to input a zoom value. For example, if a user wishes to resize an object to be 50% larger, the user must input a zoom value as shown in Figure 4-7:

Figure 4-7 Zoom function input

The zoom function is implemented based on the Paraview python class through the servermanager

module. servermanager allows the mobile client to interact with the Paraview server remotely through the gateway python script clientgateway.py. While the actual zoom is executed on the Paraview server side by running servergateway.py, as mentioned earlier, any visualisation change will need tocommunicate with the servermanager module.

Therefore, we use one of the servermanager module’s function called camera.Zoom(ndata) _{to zoom} the visualisation in the Paraview server. “(ndata)” represents the zoom value entered on the smart phone.

 Rotation function

Paraview allows users to view the object in a 2D or 3D environment. For the purpose of rotating the object to allow different views, the rotation function is essential to implement in the mobile client application.

To rotate the object displayed on the mobile client, the mobile client needs to send rotation requests first to the Paraview server through the gateway. Once the rotation requests are read and processed by the Paraview server, the gateway will then notify the mobile client and send the image through the network.

The rotation function is designed to have four text fields that allow users to move the camera vertically or horizontally, see Figure 4-8.

The four directions represent camera rotation directions. The mobile client users need to input the number of degrees to rotate the object. The rotation directions are divided into two groups:

a) Vertically

The text fields in Figure 4-8 (a) that are labelled “Rotate Up” and “Rotate Down” mean that the camera position will move vertically for the rotation.

Similar to the zoom function in the servermanager module, Paraview has a rotation function called camera.Elevation(fl1)_{. “}(fl1)_{” represents the vertical rotation value that is input by the user on the} smart phone and recorded subsequently in the gateway’s cmd.txt file.

Figure 4-8 (a) Rotation function

Figure 4-8 (b) Rotation direction for 3D object Figure 4-8 Rotation diagram

b) Horizontally

In Figure 4-8 (a), the text fields labelled “Rotate Left” and “Rotate Right” mean that the camera position will move horizontally for the rotation. In relation to the servermanager module, Paraview has the horizontal rotation function called camera.Azimuth(fl2). “(fl2)” represents the horizontal rotation value that user is input by the user on the smart phone and recorded on the gateway’s

cmd.txt file.

Figure 4-9 shows an example of a teapot rotation and a teapot zoom implemented from the mobile client application:

Figure 4-9 (a) Initial view

Figure 4-9 (b) Input parameters Figure 4-9 (c) Updated visualisations Figure 4-9 Rotation & Zoom visualisations

Figure 4-9 shows how the original teapot (Figure 4-9 (a)) can rotate and update to the larger one in the mobile client application. Figure 4-9 (b) shows that the mobile client is about to zoom in 1.5 times, move the camera up 45 degrees and then shift the camera to the right by 30 degrees. Figure 4-9 (c) displays the updated visualisation that is transmitted by the server.

In the mobile client rotation implementation process, and as mentioned in the zoom function, the rotation function is implemented based on the servermanager module. The rotation degree parameters that are input by the user are delivered in order to the gateway. Once the gateway receives the commands, it writes to a new file named “cmd.txt” stored on the gateway. As mentioned in Figure 4-3, the example of the format in cmd.txt file corresponding to the user interface.

 Representation function

The representation function uses the same text file implementation described above to allow users to change representation types for the objects being displayed. In the servermanager module, Paraview function SetDisplayProperties(vtkreader, Representation=rep) _{allows users to change the} visualisation representation. “rep” is the representation value that a user chooses from the smart phone. Users only select one type of representation at a time. The following diagram shows an example of the “Wireframe” representation of the teapot object: