Apparatus for generating a dynamic structured light pattern for optical tracking in three-dimensional space, comprises an array of lasers, such as a VCSEL laser array, to project light in a pattern into a three-dimensional space; and an optical element or elements arranged in cells. The cells are aligned with subsets of the laser array, and each cell individually applies a modulation, in particular an intensity modulation, to light from the laser or lasers of the subset, to provide a distinguishable and separately controllable part of the dynamic structured light pattern. A method of generating a structured light pattern is disclosed, in which light is provided from an array of lasers, and light is individually projected from subsets of the array of lasers to provide differentiated parts of the structured light pattern.