TerrariumXR is a fun “little” project focusing on hand interactions in mixed reality. Basically, the user can manipulate the geometry of a planet through a “dual-hand input” (DHI) system. By performing various gestures on their ‘alt’ hand, the user can change how their ‘primary’ hand interacts with the geometry. There’s a lot going on under the hood to make this possible, specifically when it comes to geometry manipulation. Built in Unity for Quest 3, it works by creating & subdividing an icosphere, separating its vertices into eight octants. Each frame, the program compares the primary hand’s position with vertices in the active octant, in order to find the nearest vertex(s). A modified grab transformer is then applied (via Meta’s XR Interaction SDK) to the relevant vertex(s).