Exploring the Valkenburg mines in virtual reality

Abstract

Bachelor students of Earth, Climate & Technology (EC&T) at the TUDelft have to do post-mining risk management assignments in the old mines in Valkenburg as part of second-year courses. They will do this by inspecting and assessing the stability of underground structures. To achieve this, a virtual reality application is created, which will be part of a larger project called VROCK. For this, 3D models have been obtained in the Valkenburggroeve and the Plankertgroeve. Selected points of interest are scanned, which are often large pillars. The points of interest are scanned using two LiDAR scanners on iPhones. An app called Scaniverse is used for scanning, which gave 3D mesh models as output. These scans result in models with a high mesh density, and thus they need to be optimized to be computationally light enough for virtual reality. This is solved using quadric error metrics using edge contraction. This method ranks every edge of the 3D mesh by the error caused by optimization, and then contracts these edges based on this ranking. The optimized models are then compared with the original versions to assess their quality as well as comparing how other scan ranges and processing modes change the optimized results. It is found that a scan range of 5 meters with the detail processing mode result in the most suitable models for virtual reality, as they show the highest texture quality with the lowest polygon count. The new optimized models are prepared for the final virtual reality application, which is made in the Unreal Engine 5.3 game engine. Multiple methods such as Level of Detail, as well as the types of levels used and lighting placement and lighting type are used to increase performance as much as possible. The XRZone at the TUDelft Library will create the full application with my processed models; however, to assess performance, a small virtual reality demo is made for players to get a feeling of the final result. A theoretical limit of 1,125,000 rendered polygons is assumed based on the virtual reality hardware; however, the results show that at most 465,478 polygons were rendered. Based on this, the performance is very well, as older hardware should also be able to work with the amount of polygons being rendered. Additionally, a survey is held to assess the quality of the game demo. Players are asked about different light intensities, motion sickness as well as if they prefer three smaller levels instead of one large level. The results of this are overall very positive, with almost all players preferring three levels instead of one.