# Influence of Material on the Density of a Point Cloud Created Using a Structured-Light 3D Scanner
## 4 Results
### Glossy Materials  
Materials that were slightly glossy have already been mentioned in the previous subsections. However, no negative effect on the resulting point cloud density was observed. To sufficiently assess the influence of this particular characteristic of the material on point cloud density, we selected some other samples which are only glossy, but meet other criteria of the ideal material, so they are not transparent or do not contain very fine elements. The samples that were selected were granite and sheet metal. The first of these materials is granite, which contains mica particles, which shine when light falls on them at different angles. As for the reflection, only vague outlines are visible in it. When scanned without any treatments, it achieved a surprisingly relatively high average point cloud density of 101,012 points per sample area; see Figure 9a. All scanning attempts had a resulting point cloud density below the 2200 points/cm\({}^{2}\) threshold. As a treatment, a dry shampoo was used for the test on the next attempt, which was supposed to cover the shiny surface. Due to this surface treatment, it was possible to cover the shiny parts. The average point cloud density increased by more than 220% in the measured area after application, and all acquired point clouds had a density above the 2200 points/cm\({}^{2}\) threshold; see Figure 9b. As can be seen in Table 3, the coefficient of variation has decreased. Figure 8: Meshes from point clouds of the first treatment surface—hairy substance (**a**), woven carpet (**b**), reed (**c**). Figure 9: Meshes of granite with a raw surface (**a**) and 1 st treatment (**b**) with dry shampoo. The second of these materials is sheet metal, which is very shiny, almost like a mirror. When scanned without any treatments, it achieved a very low average point cloud density of 14,674 points per sample area. A chalk spray was used as a treatment for the next test to cover the shiny surface. Two applications were made, first in a thin layer and then in a thick, opaque layer. Thanks to this surface treatment, it was possible to achieve its complete opacity, and the average point cloud density during the first and second applications increased by more than 770% in the measured area after the first surface treatment and by 1290% in the measured area after the second surface treatment. The meshes can be seen in Figure 10. Despite the increase in point cloud density, the threshold of 2200 points/cm\({}^{2}\) was reached only in one case of scanning activity of the material after the second surface treatment (the thick opaque layer). It is also worth noting that the application of the chalk spray also reduced unwanted noise, which was probably caused by the incorrect reflection of light from the reflective surface and could reduce the quality of the resulting model. The noise is visible when looking at the point cloud from the side and is located above but also below the surface of the cloud, which should represent the sample itself, which is only a flat surface. After the application of chalk spray, this phenomenon is largely eliminated, and on the resulting point cloud, there are more visible stripes with a higher concentration of points, which occurred especially on well-scannable smooth surfaces. The original and treated material (after the second spray application) and their meshes are shown in the following Figure 11.