## 4 Results
### The Effect of Each Factor  
In this section, each factor (camera type, its FoV, rotation, contrast ratio, a display device, and whether shadows are turned on) was investigated with regression analysis. This means that each factor was compared to the basis of the variable, its coefficient is named Intercept in each case and the level itself Intercept Level. The results of every significant comparison are presented with 95% confidence intervals (CIs) in Figure 2. It should be noted that confidence intervals can be visualized well: it is possible to observe the effects of variables, but if the confidence interval belonging to a non-basis level variable reaches zero, then there is no significant effect of this level on the test completion related to the basis. First, the effect of the camera type was analyzed. It has to be noted that a virtual camera has two types: orthogonal and perspective. The former uses orthographic projection, while the latter is similar to the human eye. 1291 tests were conducted with the former and 1418 with the latter. The former also was the Intercept variable with an estimate of 201.081 s. According to the results, the camera type does not significantly affect the completion times (\(p\)-value = 0.78). Therefore, the camera type was omitted from further analysis. Next, the influence of camera FoVs was examined. This factor had 5 levels in this study: 45\({}^{\circ}\), 60\({}^{\circ}\), 75\({}^{\circ}\), 90\({}^{\circ}\) and undefined. The latter also means that an orthogonal camera was used since the FoV is undefined in that case. 1049, 120, 134, 115, and 1291 tests were done with all these levels, respectively. Here, the Intercept level was 45\({}^{\circ}\) with an estimate of 205.586 s. As shown by the results of the regression analysis, only the 60\({}^{\circ}\) FoV has a significant effect (\(p\)-value = 0.00788): the times are decreased in this case, on average. Out of the remaining levels, 90\({}^{\circ}\) FoV was the closest to being significant (\(p\)-value = 0.10340). These insignificant factors also decreased the completion times, albeit slightly. Afterward, the camera rotation was investigated. 7 levels existed in this case: \(-\)45\({}^{\circ}\), \(-\)30\({}^{\circ}\), \(-\)15\({}^{\circ}\), 0\({}^{\circ}\), 15\({}^{\circ}\), 30\({}^{\circ}\), and 45\({}^{\circ}\). 294, 294, 106, 1251, 312, 313, and 139 tests were done with these levels, respectively. The Intercept level was \(-\)15\({}^{\circ}\) with an estimate of 236.1102 s. As can be seen, two variables have significant effects which decrease completion times: 0\({}^{\circ}\) (\(p\)-value \(<\) 2 \(\times\) 10\({}^{-16}\)), and \(-\)45\({}^{\circ}\) (\(p\)-value = 0.044). This means that in most cases, significantly smaller test completion times can be reached without camera rotation. Figure 2: 95% CIs of each significant factor. The following variable to examine was the contrast ratio: there were 5 levels in this case: 1.5:1, 14:1, 21:1, 3:1, and 7:1. Respectively, the number of tests was 1066, 164, 191, 167, and 1121. 1.5:1 was the Intercept level with an estimate of 148.378 s. As can be seen, every level has a significant influence, and each increases the completion times. The significances are the following: 3:1 (\(p\)-value = 1.13 \(\times\) 10\({}^{-5}\)), 7:1 (\(p\)-value \(<\) 2 \(\times\) 10\({}^{-16}\)), 14:1 (\(p\)-value = 0.00391), and 21:1 (\(p\)-value = 4.45 \(\times\) 10\({}^{-7}\)). The best case is contrast ratio 7:1. It means, that the contrast should be increased to a certain level, but if it is too strong, its effect decreases. Next, the existence of shadows in the scene was assessed. Therefore, there were two levels: shadows are turned on (1414 tests), and shadows are turned off (1295 tests). The latter was the Intercept level with an estimate of 193.355 s. According to the results, when shadows are turned on, the completion times are significantly increased (\(p\)-value = 0.00447). It means, that the lack of shadow is better. Its existence could be confusing. Lastly, the used display device was assessed.