# A Novel Method Using 3D Interest Points to Place Markers on a Large Object in Augmented Reality
## 3 Experiment and Discussion
### Experimental Environment and Methodology
#### 3.1.1 Experimental Environment  
Both experiments were conducted using Microsoft HoloLens 2, which is capable of spatial awareness of surroundings [25]. This device provides a more reliable camera pose estimation than popular AR devices, such as ARKit and ARCore [26]. In addition, this device is capable of robust pose estimation (for example, in [27], the mean error between a real and captured space when moving about 287 m in an indoor environment was 2.4 cm).  
The experiments were conducted in an indoor parking lot, as shown in Figure 11, to ensure stable illumination. Because the illumination of this environment is determined by indoor lighting, it is relatively more stable than outdoor environments, which change in real time due to the sun, clouds, etc.  
The experiments were conducted after sunset and before sunrise to maintain constant lighting. The civil twilight period was also excluded to minimize the influence of sunlight. The illuminance of the experimental location was measured between 100 and 200 lx during these times, and HoloLens's ability to augment virtual objects does not degrade at these illuminations according to a previous study [28].  
Figure 10: Example of MPS score calculation according to \(k\) and \(w\): (**a**) \(k=4\); (**b**) \(k=6\); (**c**) \(k=8\).  
Real objects  
In the experiments, cars, which are commonly seen in everyday life, were used as large objects. Two types of cars with different sizes were used as large objects, as shown in Figure 12: Kia-Morning (=Picanto) 3 rd generation 1 st facelift (hereafter DM) and Hyundai-Avante 6 th generation early model (hereafter DA). The specifications for each real object are listed in Table 3.  
2 Virtual objects  
We used models created by measuring actual cars, from the 3D model providers CGTrader [29] and Hum3D [30], as virtual objects for each real object. CGTrader is the world's largest supplier of 3D models, and it has been used in many studies. In particular, Ref. [31] studied autonomous driving using a real car and a corresponding virtual object in  
Figure 11: Indoor parking lot of the Future-Learning Center, Korea University of Technology and Education, where the experiments were conducted.  
Figure 12: Real objects used in the experiments: (**a**) DM\({}_{\text{R}}\); (**b**) DA\({}_{\text{R}}\). where an object with the subscript R denotes a real object.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Type** & **DM\({}_{\text{R}}\)** & **DA\({}_{\text{R}}\)** \\ \hline Overall length & 3595 & 4570 \\ Overall width & 1595 & 1800 \\ Overall height & 1485 & 1440 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Specifications of real objects (unit: mm).  
the CGTrader. Hum3D is a company that aims to create realistic modeling for applications such as AR and visualization, and 3D experts examine whether the modeling results match actual objects. This company is primarily used in research on cars [32; 33; 34].  
As virtual objects, 3D models identical to the car models (e.g., Kia-Picanto 3 rd generation 1 st facelift) of the real objects were used [35; 36]. To verify the equivalence of the virtual models to the real objects, it was checked whether they met the tolerances in Article 115 \"Tolerance of Specifications\" of the \"MOLIT Ordinance: Regulations for Performance and Safety Standards of Motor Vehicle and Vehicle Parts\".  
The results showed that they all met the tolerances, as listed in Tables 4 and 5 (note that Ref. [36] was created at a 1/2 scale, so the comparison was performed after scaling up to 2\(\times\)). Except for the overall height, all the error rates were less than 1%. This is likely due to the influence of consumable components such as fires on this value.  
Because they are virtual models, they may differ from real objects owing to options and consumables, as well as the geometric discrepancy problem. For this reason, consumable wippers, tires, and license plates were removed from the virtual models, and the issue of options is considered as the geometric discrepancy problem in this paper.