1. A system comprising: one or more processors; one or more cameras to obtain at least a first 3D image of an environment at a first time and a second 3D image of the environment at a second time subsequent to the first time; one or more computer-readable media storing computer-executable instructions that, when executed by the one or more processors, cause the one or more processors to perform acts comprising: detecting a first hand segment in the first 3D image; detecting a second hand segment in the second 3D image; identifying a first continuous surface in the first 3D image corresponding to the first hand segment; determining first 3D boundaries of the first continuous surface; generating a first contour of the first hand segment based, at least in part, on the first 3D boundaries of the first continuous surface; identifying a second continuous surface in the second 3D image, the second continuous surface corresponding to the second hand segment; determining second 3D boundaries of the second continuous surface; generating a second contour of the second hand segment based, at least in part, on the second 3D boundaries of the second continuous surface; determining whether a region defined by the second contours of the second hand segment overlaps with a region defined by the first contour of the first hand segment; and determining that the first hand segment and the second hand segment are a same respective hand segment when an amount of overlap between the region defined by the second contours of the second hand segment and the region defined by the first contours of the first hand segment satisfies a threshold amount.