3D Graphics and Virtual Reality (Example answers 1)
Section A ( 6 marks )
Pick any three of the following :
- Video mapping.
This form of VR monitors the user with a camera and provides feedback by displaying the user's image on screen. The virtual environment is overlaid onto the user's image no screen and interaction is provided by interpreting gestures.
- Immersive VR.
This form of VR attempts to completely submerge a user within the virtual environment. A head mounted display is normally used to completely enclose the user's field of vision. Head tracking devices monitor the orientation of the user's head and update the display accordingly.
Telepresence links remote sensors and cameras in the real world with an interface to a human operator. Such systems are used widely in hostile environments or life threatening situations.
- Augmented reality.
Augmented reality overlays a virtual environment or information onto a user's normal field of vision. The user is not fully submerged within the environment and is aware of their real world surroundings. An example of such a system is the Head Up Display (HUD) in many modern aircraft.
- Fish Tank VR.
Fish tank VR is a hybrid system which uses a standard desktop monitor as the display, but incorporates LCD shutter glasses to provide a stereoscopic view. A head tracking device is also used to monitor the user's head movements and update the viewpoint accordingly. This provides a heightened sense of 3D viewing due to the effects of motion parallax providing depth cues.
Section B ( 3 marks )
A typical flight simulation system would use a model cockpit mounted on hydraulic jacks. These jacks can induce movement in the cockpit to provide a sense of motion within the virtual environment. The windows of the cockpit view the computer generated virtual environment that reacts accurately to flight control input and any scenarios programmed into it. The advantage of using such a system means that emergency procedures and potentially life threatening situations can be safely reproduced and used as a training exercise.
Section C ( 6 marks )
The three conventions which you must consider when working with a new 3D co-ordinate system are:
- The orientation of the axes.
You must first establish which axes are pointing in which direction. The X axis is almost always lying from left to right, but the Y and Z axes are often interchanged. Effectively you must determine which axes is "up".
- The sign of the axes.
Once we have established which axes go where, we need to determine which part of each axis is positive and which is negative. We use the right or left handed rules to determine this.
- The sign of rotations.
Finally, we need to determine which direction is a positive rotation about any given axis. Convention uses either the left or right handed grip rule to determine this.
The following example shows a convention using the Y axis as up and the Z axis to represent depth. A right handed co-ordinate system is used, and the direction of positive rotation is shown using the right hand grip rule.
Section D ( 2 marks )
- Roll describes rotations about the Z-axis
- Pitch describes rotations about the X-axis
- Yaw describes rotations about the Y-axis
Section E ( 3 marks )
One sequence you could use is as follows (note: there may be another equally correct answer).
[Roll -90° ][Pitch 90° ][Yaw 0° ]
( Total 20 )