1. A system, comprising: a processor; and a memory communicatively coupled to the processor when the system is operational, the memory bearing processor-executable instructions that, in response to execution by the processor, cause the system to at least: receive a depth image of a scene; determine a centroid of a target in the scene; define a bounding box for the target based on the centroid of the target and a measurement of the target; and identify a pixel of the depth image that is outside of the bounding box as being associated with an environment of the scene.