## 4 Experimental Setup and Procedures
### Experimental Procedure
The avatars on PC moved in the direction of the green arrows, repeatedly through the points P1, P2, P3, P4, P1, P5, P6 and P7. Random excursions were implemented to have some variety in the trajectories. How the scene looked with 20 moving users, represented by client apps on PC, can be seen in Figure 8b. For the smartphone and MS HoloLens, the movement was performed by one of the experimentalists, holding or wearing the device. The experimentalist followed a similar trajectory, but on a smaller area as the avatars of the PC client apps. The area is depicted as the white rectangle in Figure 8a, and the experimentalist walked repeatedly through the points P1, P2, P8, P4, P1, P5, P9 and P7 (the blue dashed line). To ensure that the recorded performance measures were not affected by the server machine (SRV) using all of its resources, its performance was observed during the experiments. The corresponding measurements included CPU and memory (RAM) usage and were performed on the operating system level at SRV. In all experiments, both the CPU and RAM usage was below 60%. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Experiment**} & \multirow{2}{*}{
\begin{tabular}{c} **Subject** \\ **(Component)** \\ \end{tabular} } & \multicolumn{4}{c}{**Number of Client Devices**} \\ \cline{3-5}  & & **PC** & **PH** & **HL** \\ \hline E.ECA.1 & ECA & 1 & 0 & 0 \\ E.ECA.5 & ECA & 5 & 0 & 0 \\ E.ECA.10 & ECA & 10 & 0 & 0 \\ E.ECA.15 & ECA & 15 & 0 & 0 \\ E.ECA.20 & ECA & 20 & 0 & 0 \\ E.6 DF.1 & 6-DoF SMC & 0 & 1 & 0 \\ E.6 DF.5 & 6-DoF SMC & 4 & 1 & 0 \\ E.6 DF.10 & 6-DoF SMC & 9 & 1 & 0 \\ E.6 DF.15 & 6-DoF SMC & 14 & 1 & 0 \\ E.6 DF.20 & 6-DoF SMC & 19 & 1 & 0 \\ E.HL.1 & HoloGOM & 0 & 0 & 1 \\ E.HL.5 & HoloGOM & 4 & 0 & 1 \\ E.HL.10 & HoloGOM & 9 & 0 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Subjects of individual experiments and devices used. The numerical values of the statistics in Figure 9 (minimum, average (mean) and maximum) can be found in Tables 3 and 4. Tables 3 and 4 also provide the sample standard deviation (std) for the collected data sets. Each set of statistics is given for the dataset collected with the corresponding component first, and then for the set collected without the component. By the corresponding component, we mean the component that was the subject of the experiment. The last row (FR.drop) tells us how the frame rate decreased after the corresponding component had been employed. It is computed as the percentage of the average frame rate without the component, according to (2). \[FR.drop\;(\%)=100\%*(avg_{fn}-avg_{fgy})/avg_{fn} \tag{2}\]  
In (2), \(avg_{fn}\) is the average frame rate without the proposed component and \(avg_{fgy}\) is the average frame rate with the component. The most significant frame rate drop was  
Figure 9: Min-max-average charts comparing the frame rate in frames per second with and without the ECA (**top**), 6-DoF SMC (**middle**) and HoloGOM (**bottom**) component under various loads. The complete data can be seen in [[http://lirkis.kpi.fei.tuke.sk/wp-content/collVREvalScPIFps.png](http://lirkis.kpi.fei.tuke.sk/wp-content/collVREvalScPIFps.png)]([http://lirkis.kpi.fei.tuke.sk/wp-content/collVREvalScPIFps.png](http://lirkis.kpi.fei.tuke.sk/wp-content/collVREvalScPIFps.png)) (accessed on 22 April 2021). observed with the 6-DoF SMC component (36.07% on average), followed by HoloGOM (29.1%). On the other hand, the ECA component had negligible influence (4.03%).