An additive manufacturing apparatus includes a platform, a dispenser to deliver a plurality of layers of feed material, one or more light sources configured to emit a first light beam and a second light beam, and a polygon beam scanner including a rotatable mirror having a plurality of reflective facets to redirect the first light beam and the second light beam toward the platform to deliver energy to an uppermost layer of feed material. The mirror is positioned and rotatable such that motion of each facet of the plurality of reflective facets causes the first light beam to sweep along a first path on the uppermost layer and causes the second light beam to sweep along the first path following the first light beam.