14. Underscanning

In a volumetric rendering system like PresenZ, the amount of data collected for a surface depends on the surface’s distance from the ZOV. The closer a surface is to the ZOV, the more points are needed to represent it accurately in the rendered image, because it occupies more space in the ZOV. Therefore, the point density will be higher for closer surfaces compared to surfaces further away. This is why the underscanning system is designed to reduce the amount of data collected for surfaces close to the ZOV, while still maintaining an acceptable level of accuracy.

Underscanning is a system used to reduce the amount of data collected while rendering surfaces close to the ZOV. Its aim is to keep the collected data above a minimum point size for optimal display in a VR headset. The default setting for the minimum point size is 1mm, which is suitable for a resolution of 3024x2018. The system has four compression levels available, which are automatically selected based on the resolution and surface distance.

The compression levels and factors are as follows:

Compression levels	0	1	2	3
Compression factors	1x	2x	6x	24x

Note

It should be noted that if a scene has objects very close to the ZOV and the rendering times and file sizes are too high, increasing the minimum point size might be beneficial. Additionally, the compression level can be manually influenced using the “minimum point size” parameter in the PresenZ user interface. The larger the point size, the greater the compression factor will be.