# A Personalised Emotion-Based Model for Relaxation in Virtual Reality
## 4 Use Case Implementation
### Emotional Model  
The emotional model is implemented for the presented VEs. Based on the adaptations found in Table 1 the formulas in Section 3.2 are completed. Table 3 shows the range of values for each adaptation as well as the weights they are given for each of the formulas. The adaptations are discussed in more detail. First, artificial light (\(al\)) corresponds to light artificially produced, e.g., a light bulb. The light intensity scales linearly between 0 and 1, where 0 is no light and 1 is maximum light. This artificial light will only be present for indoor environments. Second, natural light (\(nl\)) denotes naturally produced light, such as the sun. The light intensity scales linearly between 0 and 1, where 0 is late at night (low light) and 1 is around noon (maximum light). Light has a significant impact on arousal [35]. \begin{table}
\begin{tabular}{c l l} \hline
**No.** & **Question** & **Possible Answers** \\ \hline
1 & Would you prefer an indoor or outdoor environment to relax? & [indoor, outdoor] \\
2 & Could the presence of water help you to relax? & [yes, no] \\
3 & Are you afraid of heights? & [yes, no] \\
4 & What is you favourite season? & [summer, winter] \\
5 & How does having a calm campfire nearby make you feel? & \{relaxed, anxious] \\
6 & How do you feel when a dog is in your presence? & [relaxed, anxious] \\
7 & How does darkness make you feel? & [relaxed, anxious] \\
8 & How do you find classical relaxation music? & \{very relaxing, not relaxing at all] \\
9 & Blue light gives you a relaxed feeling, do you agree? & \{agree, disagree\} \\
10 & How afraid do you feel right now? & \{not at all, very much\} \\
11 & How stressed do you feel right now? & \{not at all, very much\} \\
12 & How aroused do you feel right now? & \{not at all, very much\} \\ \hline \end{tabular}
\end{table} 
Table 2: The amount of possible answers that can be given to every question from the questionnaire. Figure 6: Decision tree used by the environment selector. Therefore, the system has to control the parameters for light. Third, it has been shown that the colour of artificially created light has a strong influence on the relaxation of the user [37]. Therefore, we defined the adaptation light colour (\(lc\)). If artificial light is activated, the colour of the light can be set. The colour of the lights scales linearly between white and blue light, where 0 is with white light and 1 is blue light. The fourth adaptation is the fire (\(py\)). It has been shown that a source of fire, such as a fireplace or an outdoor campfire, can be relaxing for some users [38], while at the same time fire can distress people with pyrophobia. The intensity of the fire scales linearly between 0 and 1, where 0 is no fire and 1 is a large fire. The fire adaptation is only defined for the outdoor environment. Fifth, for both the indoor and outdoor environments, it is possible to add a dog. The dog adaptation (\(dg\)) activates a dog playing around unless the user prefers otherwise. Dogs have proven to provide comfort and reduce stress in patients [39]. The distance of the dog to the user can be controlled choosing from three values, where for 0 the dog is far away, for 1/2 the dog is closer and for 1 the dog is very close. Music has shown very good results to induce relaxation. Therefore, music is also set as a part of the adaptation set. When music (\(ms\)) is selected, relaxation music (indoor) or sounds (outdoor) are playing in the background, e.g., birds. The music can be turned on (1) or off (0). Finally, control breathing (\(cb\)) provides a visual aid for a controlled breathing exercise. This visualisation is either turned on (1) or off (0). Based on the adaptations, for this use case, we defined three sources of fear which are modelled with the \(f(a_{x})\) function defined in Equation (7). These are pyrophobia, cynophobia [40] and nytophobia [41]. Pyrophobia is the fear of fire. It is therefore induced by the fire adaptation (\(f(a_{py})\)). Cynophobia, or fear of dogs, is induced by the dog adaptation (\(f(a_{dg})\)).