Rendering Tree Roots Outdoors: A Comparison Between Optical See Through Glasses and Smartphone Modules for Underground Augmented Reality Visualization - Gergana Lilligreen; Philipp Marsenger; Alexander Wiebel (Virtual, Augmented and Mixed Reality - 13th International Conference, VAMR 2021, Held as Part of the 23rd HCI International Conference, HCII 2021, Virtual Event, July 24-29, 2021, Proceedings, 2021)